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Limited use of stored energy reserves for reproduction by the tropical loliginid squid Photololigo sp
Abstract
This study sought to determine if the tropical loliginid squid Photololigo sp. stores energy in the form of lipid, carbohydrate or protein for reproductive investment. Individuals were examined for changes in morphometry, mantle muscle structure and concentrations of water, lipid, carbohydrate and protein in muscle tissue and the digestive gland, associated with the stage of reproductive maturation. Muscle mass was affected by reproductive maturation in females. Mature individuals were lighter for their length compared with females in the early stages of maturation. Concentrations of lipid and carbohydrate in the muscle tissue were very low, and female Photololigo sp. showed equivocal evidence of declining lipid and carbohydrate levels with egg production. There was no evidence of dramatic changes in protein concentration in the mantle muscle with reproductive maturation. Male Photololigo sp. showed a change in the digestive gland with maturation, with water content increasing and protein concentrations decreasing. The digestive gland of both male and female Photololigo sp. increased in size and contained less water with growth. There was little evidence that the storage and transfer of energy for reproduction occurred in Photololigo sp. Instead, it is probable that energy for reproduction is predominantly sourced directly from consumed food.
... The energetic cost of reproduction can be measured at various levels: whole animal, cellular organization, or tissue composition, with most authors having studied this cost of reproduction in cephalopods through morphometric analyses (e.g., Collins et al., 1995;Ho et al., 2004;Otero et al., 2007;Smith et al., 2011;Lourenço et al., 2012;Lin et al., 2015), and just a few focusing on studying changes in the structural composition (e.g., Moltschaniwskyj, 1995;Moltschaniwskyj and Carter, 2013) or through detailed biochemical analyses (e.g., de Moreno et al., 1998;Moltschaniwskyj and Semmens, 2000). Structural and/or biochemical analyses throughout maturation unlike morphometric analysis are more desirable because they offer a more detailed knowledge of patterns of energy storage and utilization to gain a comprehensive understanding of the interaction between the organism and its environment, and may reveal where constraints of power budgeting are most critical (Clarke et al., 1994). ...
... However, most analyses on biochemical changes throughout reproduction in cephalopods suffer from the lack of information during post-spawning, and this is more pervasive for those species, such as some octopods, which hide for parenting. Nonetheless, some studies have dealt with the biochemistry of maturation in a number of female cephalopod species finding some common patterns such as the accumulation of lipids and/or proteins in the ovary (e.g., Jackson et al., 2004), and a stable composition in the mantle, particularly with regard to proteins, during maturation (Clarke et al., 1994;de Moreno et al., 1998;Moltschaniwskyj and Semmens, 2000;Moltschaniwskyj and Carter, 2013). Regarding octopods, those particularities outlined previously are also common, for instance, the accumulation of lipids in the ovary (Pollero and Iribarne, 1988;Rosa et al., 2004b) and in the digestive gland in some cases (Lourenço et al., 2014;Pascual et al., 2020). ...
... During sexual maturity, both somatic and reproductive growth would occur simultaneously, though reallocating part of the energy from the somatic growth to ovary growth once vitellogenesis starts (macrostage III, Sieiro et al., 2014) but without any deterioration of the soma, i.e., trade-offs, as happens in other cephalopods (e.g., Quetglas et al., 2011;Moltschaniwskyj and Carter, 2013). Therefore, the energy for ovary growth would come directly from food agreeing with previous findings for the same species (Rosa et al., 2004a;Otero et al., 2007) and other cephalopods (Moltschaniwskyj and Semmens, 2000;Rosa et al., 2005a). ...
The common octopus, Octopus vulgaris, has a short life cycle, growing rapidly to maturity, spawning once, and characterized by an asynchronic oocyte development and a synchronic ovulation dying after breeding. This species has a protein and amino acid metabolism and it is usually defined as an income breeder. However, most biochemical studies lack an examination of the whole reproductive cycle, in particular the spawning process. We here studied the biochemical changes and determined the energy strategy along reproduction in female O. vulgaris, and found that proteins were the main energy reserve, primarily located in the body muscle when sexually maturing and decreasing during breeding. Lipids were also an important source of energy in the ovary and digestive gland and decreased during breeding too. By contrast, glycogen had a minor contribution to the energy content and was the unique compound that increased in spawning and post-spawning females. Additionally, the most abundant fatty acids (FA) in all tissues were 16:0, 18:0, 20:1n9, 20:4n6 (ARA), 20:5n3 (EPA) and 22:6n3 (DHA), with a clear predominance of long-chain polyunsaturated FA. The FA profile of mature ovaries was compared with other life stages finding similitudes with eggs, hatchlings and juveniles but considerable differences with paralarvae which showed higher DHA/ARA and EPA/ARA ratios. Therefore, we found important biochemical changes along the reproductive cycle that determined the energetic signature in each tissue, though no significant energy trade-offs between tissues were found, suggesting that, on the one hand, female O. vulgaris obtained energy directly from food accumulated simultaneously in the somatic and reproductive tissues during sexual maturation. However, an energy reallocation from somatic to reproductive growth would occur once vitellogenesis has started, so that the rate at which body growths would decrease in favor of ovary growth. On the other hand, during breeding, a general decrease in the energy content occurred in all tissues, so that the ovary would be responsible for the spawning success, whereas muscle tissues and digestive gland would independently supply the energy needed for the body maintenance safeguarding the female survival needed for the maternal care.
... Los componentes comúnmente analizados para la comprensión de la dinámica de reserva y gasto energético en cefalópodos, son las fluctuaciones en la concentración de lípidos, carbohidratos, proteínas, aminoácidos, ácidos grasos, colesterol, glucógeno y en algunos casos contenido energético, humedad, ceniza y hemolinfa; mientras que los principales tejidos comparados son la gónada (ovario), la glándula digestiva y el músculo del manto (Pollero e Iribarne, 1988;Castro et al., 1992;Clarke et al., 1994;Moreno et al., 1998;Gabr et al., 1999; Moltschaniaskyj y Semmens, 2000;Rosa et al., 2002Rosa et al., , 2004aRosa et al., , 2004bRosa et al., , 2005aRosa et al., , 2005bZamora y Olivares, 2004;Reyes et al., 2008;Cruz-López, 2010;García-Garrido et al., 2010). ...
... Estudios realizados en calamares sugieren que la evidencia de almacenamiento o transferencia de energía entre tejidos para la reproducción es reducida o inexistente, señalando que la energía para la reproducción proviene directamente del consumo de alimento (Moltschaniaskyj y Semmens, 2000;Rosa et al., 2005b). Un único estudio sugiere la posibilidad de movilización de energía a partir del tejido muscular, sin embargo esto es realizado sólo con base en la observación de las fibras que componen este tejido (Moltschaniwskyj, 1995). ...
... En lo que respecta a los triglicéridos, éstos también mostraron decrementos significativos en la glándula digestiva, pero en este caso durante el desove y postdesove; por lo que se trata de un descenso más bien atribuible al mantenimiento del organismo durante el ayuno reproductivo, pues a pesar de que los lípidos no son reconocidos como la principal fuente energética en cefalópodos, estudios han demostrado la capacidad de algunos pulpos para movilizar reservas de triglicéridos de la glándula digestiva para suplir hasta el 30% de la energía necesaria durante periodos de inanición (Moltschaniwskyj y Semmens, 2000;García Garrido et al., 2010-, Morillo-Velarde et al., 2012Navarro et al., 2014). ...
Todo conocimiento sobre la reproducción y nutrición de una especie es importante para su entendimiento, cultivo y manejo como recurso. Esto incluye el estudio de la fisiología reproductiva, evento particularmente demandante de energía en organismos semélparos como los pulpos. En el presente trabajo se analiza el efecto de la maduración gonádica en la composición bioquímica y dinámica energética del pulpo O. hubbsorum. Para ello se recolectaron hembras de la especie en la Bahía de La Paz, BCS., de agosto a noviembre de 2013. Se realizó histología de las gónadas para definir las fases de madurez gonádica. La dinámica energética se analizó agrupando los datos de acuerdo a estas fases y mediante tres aspectos: 1) Comparación de pesos de órganos reproductivos y somáticos; 2) Variación de índices morfofisiológicos (IGS: índice gonadosomático, IGD: índice de la glándula digestiva, IM: índice muscular); y 3) Análisis bioquímicos en ovario, glándulas oviductales, glándula digestiva y músculo; obteniéndose valores de energía mediante factores de conversión establecidos. Entre las 118 hembras obtenidas, se encontraron representadas las seis fases de desarrollo gonádico descritas para la especie: inmadurez I y II, maduración, predesove, desove y postdesove. Los pesos y tallas generales y de órganos incrementaron principalmente durante el predesove y desove, siendo la glándula digestiva el órgano que creció más durante la inmadurez y perdió más peso en el postdesove, sugiriendo la utilización de reservas de este órgano para el ayuno reproductivo. Esto fue confirmado por la correlación entre el IGS y el IGD, y es explicado por la composición bioquímica como una disminución significativa en el contenido de triglicéridos durante el postdesove, atribuible al mantenimiento energético durante la inanición. Asimismo, la relación PG-PGD por fases, reveló que los recursos de esta glándula también son utilizados para la vitelogénesis durante el predesove; lo que, de acuerdo al análisis bioquímico, corresponde a un transporte de lípidos hacia el ovario y las glándulas oviductales, necesarios para la formación del vitelo y fuente de ácidos grasos respectivamente. Por su parte, la relación IGS-IM demostró un transporte de recursos musculares para la maduración gonádica, en este caso correspondiente a proteínas, encontrándose evidencia bioquímica que indica un transporte de este sustrato hacia el ovario y, principalmente, hacia las glándulas oviductales durante el predesove, atribuible a la formación del vitelo y las mucoproteínas para el recubrimiento de los huevos respectivamente. En cuanto al contenido de carbohidratos totales y glucógeno, éstos también fueron requeridos durante la maduración gonádica, sin embargo no se encontró
evidencia de su transporte entre órganos por lo que su adquisición se atribuye enteramente a la alimentación recientemente ingerida. Los carotenoides constituyeron un sustrato sin relación con la maduración gonádica o el ayuno reproductivo, con una acumulación constante únicamente en la glándula digestiva, atribuible a la dieta. Energéticamente, el efecto más significativo de la maduración sexual corresponde a un incremento en el contenido energético del ovario, debido a la actividad de síntesis por vitelogénesis. El mayor costo energético en O. hubbsorum corresponde a lípidos, representando una inversión del 74.9% en el ovario y del 66% en la glándula digestiva; y a proteínas, implicando un gasto del 64% en el músculo. Cabe destacar que los resultados del presente trabajo difieren en gran medida a estudios con otros octópodos, demostrando que las necesidades y procesos metabólicos pueden variar notablemente entre especies. Sin embargo, se encontraron mayores similitudes con el pulpo O. mimus, aunque son necesarios más estudios comparativos entre especies. En conclusión, O. hubbsorum presenta un ciclo de almacenamiento y utilización de reservas energéticas que indican una estrategia reproductiva de tipo conservativo, en la que la maduración gonádica, particularmente el predesove, depende estrechamente de las reservas energéticas almacenadas en la glándula digestiva y el músculo.
... To study the relative investment between somatic and gonad growth, the geometric mean regression (Model II) equations for ML-MW, ML-FW, ML-DGW, ML-gonad weight were calculated separately for males and females. From these equations, the residuals were estimated for each specimen and used as size-independent measure of tissue and somatic condition (Moltschaniwskyj & Semmens, 2000;García-Berthout, 2001;Green, 2001;Pecl, 2001;McGrath Steer & Jackson, 2004;Otero et al., 2007;Ceriola & Jackson, 2010). The ML-gonad weight residuals were correlated with ML-FW residuals, ML-MW residuals, and ML-DGW residuals for each sex separately. ...
... The ML-gonad weight residuals were correlated with ML-FW residuals, ML-MW residuals, and ML-DGW residuals for each sex separately. This type of analysis can highlight possible trade-offs occurring between somatic and reproductive apparatus growth (Moltschaniwskyj & Semmens, 2000;Pecl, 2001;Mc-Grath & Jackson, 2002;McGrath Steer & Jackson, 2004;Otero et al., 2007;Ceriola & Jackson, 2010). ...
... Moltschaniwskjy & Semmens, 2000;Semmens, 2002). Furthermore, the lack of correlation between digestive gland weight and gonad weight suggests that lipid reserves are not directly diverted from this organ to fuel the gonad maturation process. ...
Life span, growth and cost of reproduction of Illex coindetii were examined for the first time in the southern Adriatic Sea, central Mediterranean Sea. Age and growth were investigated through statoliths reading. Cost of reproduction was explored by studying the relative investment between somatic and gonad growth. The life span of I. coindetii was less than nine months in both sexes. Females (128-234 days) showed longer life span than males (124-178 days). In both sexes the linear model best described the mantle length-at age data, while the exponential model provided the best fit to the total weight-at-age data. In terms of mantle length, females grew faster than males (average growth rate was 1.33 mm day- 1 in females and 1.00 mm day-1 in males). In terms of total weight, no significant differences were highlighted between growth curves of males and females. Mantle length, total weight, mantle weight and fin weight increased up to the latest maturity stage in both sexes. Immature and maturing individuals showed poorer body condition than mature counterparts in both sexes. Some evidences of a reproductive strategy more similar to a multiple-spawning than to a single-spawning species were found.
... Investment in reproduction or the optimal trade-off between investment in reproduction and investment in somatic growth may be impacted by low internal energy reserves at the beginning of the breeding season (Elkin & Reid 2005). Under this circumstance, animals must optimally allocate the limited energy from food intake to maintain somatic growth and to meet costs associated with reproduction (Wells & Clarke 1996;Moltschaniwskyj & Semmens 2000). ...
... These monocyclic animals have evolved an adaptive response to the concurrent energy demands of reproduction and continued somatic growth and muscle function (Moltschaniwskyj & Carter 2013). Both protein in the mantle muscle tissue and lipid in the digestive gland have been suggested as possible substrates and sites for energy storage in cephalopods (O'Dor & Wells 1978;Castro et al. 1992;Clarke et al. 1994;Moltschaniwskyj & Semmens 2000). ...
... Many species of coleoid cephalopods exhibit a mix of capital and income breeding patterns, with energy for reproduction derived predominantly from the diet. Nonetheless, these animals need to acquire a threshold level of somatic condition so that either subsequent food intake can be fully directed to reproduction (i.e., Photololigo sp.; Moltschaniwskyj & Semmens 2000), or a diversion of energy from somatic tissues to reproductive tissues can occur (i.e., Loligo forbesi STEENSTRUP 1857; Collins et al. 1995). ...
Energy investment in reproduction and somatic growth was investigated for summer spawners of the Argentinean shortfin squid Illex argentinus in the southwest Atlantic Ocean. Sampled squids were examined for morphometry and intensity of feeding behavior associated with reproductive maturation. Residuals generated from length-weight relationships were analyzed to determine patterns of energy allocation between somatic and reproductive growth. Both females and males showed similar rates of increase for eviscerated body mass and digestive gland mass relative to mantle length, but the rate of increase for total reproductive organ weight relative to mantle length in females was three times that of males. For females, condition of somatic tissues deteriorated until the mature stage, but somatic condition improved after the onset of maturity. In males, there was no correlation between somatic condition and phases of reproductive maturity. Reproductive investment decreased as sexual maturation progressed for both females and males, with the lowest investment occurring at the functionally mature stage. Residual analysis indicated that female reproductive development was at the expense of body muscle growth during the immature and maturing stages, but energy invested in reproduction after onset of maturity was probably met by food intake. However, in males both reproductive maturation and somatic growth proceeded concurrently so that energy allocated to reproduction was related to food intake throughout the process of maturation. For both males and females, there was little evidence of trade-offs between the digestive gland and reproductive growth, as no significant correlation was found between dorsal mantle length-digestive gland weight residuals. The role of the digestive gland as an energy reserve for gonadal growth should be reconsidered. Additionally, feeding intensity by both males and females decreased after the onset of sexual maturity, but feeding never stopped completely, even during spawning.
... Maturation, somatic condition, and growth Ratios calculated from somatic and reproductive measurements are not size-independent (Hayes and Shonkwiler, 2001), but residuals of the mantle weighteML relationship provide a size-independent measure of the condition of an individual at the whole animal level (Moltschaniwskyj and Semmens, 2000). To obtain measures of somatic condition, mantle weighteML geometric mean linear regression (Model II) equations were calculated for males and females separately using log-transformed data, and from these equations, residuals were calculated for each individual. ...
... Captive female Loligo pealei (Maxwell and Hanlon, 2000) and Idiosepius pygmaeus (van Camp, 1997) also lay smaller batches of eggs more frequently or larger batches less frequently. This dichotomy in reproductive strategy adopted by individuals within a population appears common for cephalopods (Boyle et al., 1995;Moltschaniwskyj, 1995a) and has been suggested to be a function of when energy reserves are available for gametogenesis (Moltschaniwskyj and Semmens, 2000). This study suggests that seasonal differences in biotic and abiotic conditions experienced by individual squid may play a large role in determining when energy is made available for reproduction. ...
... Sepioteuthis australis has a high degree of plasticity in its life history processes in terms of growth, reproduction, and repro-somatic investment, and such flexibility in life history strategy within populations is consistent with an opportunistic lifestyle (Moltschaniwskyj and Semmens, 2000). This study revealed little evidence of trade-offs between reproduction and growth or condition of individuals. ...
2006. Life history of a short-lived squid (Sepioteuthis australis): resource allocation as a function of size, growth, maturation, and hatching season. e ICES Journal of Marine Science, 63: 995e1004. Many cephalopods continue growing while laying multiple egg batches over the adult life, with repro-somatic allocation continuing beyond attainment of reproductive maturity. Many species show extreme individual variation in reproductive investment. Factors driving this variation in adult Sepioteuthis australis were evaluated by examining allocation of energy to somatic and reproductive growth as a function of body shape, growth rate, maturation, and hatching season. Hatching season influence was sex-specific; males hatched in warmer months had greater reproductive investment, faster growth, and better somatic and repro-ductive condition, whereas females hatched in spring and summer had less reproductive investment. Seasonal impacts on life history resulted in an ''alternation of generations'', with slow-growing squid in poor condition and with high levels of reproductive investment producing a generation with completely different life-history characteristics. This suggests that abiotic and biotic conditions that change seasonally could play a large role in determin-ing energy allocated to reproduction. However, this was not driving trade-offs between size and number of offspring. Life-history trade-offs should be detectable as negative correla-tions between relevant traits. However, in Sepioteuthis australis there was little evidence of trade-offs between reproduction and growth or condition of individuals, suggesting a ''live for today'' lifestyle.
... Se ha documentado un decrecimiento progresivo del peso de la glándula digestiva en períodos de inanición (Castro et al., 1991) sugiriendo esto que funciona como reservorio de energía, pero no evidencia que provea energía para el desarrollo gonadal (Gabr et al., 1999a ). Estudios más actualizados han demostrado que en sepiólidos y loligínidos, el funcionamiento de la glándula digestiva no sería un lugar de reservorio energético en períodos reproductivos (Gabr et al., 1999aGabr et al., , 1999b Moltschaniwskyj & Semmens, 2000). Todos estos estudios sobre los tipos de funcionamiento de la glándula digestiva en algunas especies de cefalópodos, contrasta con la función (reservorio energético) constatada en el hígado de peces, durante períodos reproductivos o de escasez de alimento (Santos et al., 1996; Jobling, 1995). ...
... Se sugiere para estudios posteriores indagar acerca de un incremento en la tasa de alimentación durante el desarrollo gonádico, lo cual podría dar respuesta a la demanda energética generada en esta etapa, para suplir esta necesidad reproductiva (coincidiendo con Mangold et al., 1993) e investigar además, la premisa de que algunas especies de cefalópodos derivarían gran parte de su energía obtenida de la alimentación para la producción gonadal, incrementando su tasa de ingestión (Rocha et al., 1994). Además cabe mencionar que en los cefalópodos existen reservas energéticas en órganos tales como el manto, los músculos y las vísceras (O'Dor & Wells, 1987; Moltschaniwskyj & Semmens, 2000 ) y que éstas están constituidas principalmente de proteínas y carbohidratos (Moltschaniwskyj & Semmens, 2000). ...
... Se sugiere para estudios posteriores indagar acerca de un incremento en la tasa de alimentación durante el desarrollo gonádico, lo cual podría dar respuesta a la demanda energética generada en esta etapa, para suplir esta necesidad reproductiva (coincidiendo con Mangold et al., 1993) e investigar además, la premisa de que algunas especies de cefalópodos derivarían gran parte de su energía obtenida de la alimentación para la producción gonadal, incrementando su tasa de ingestión (Rocha et al., 1994). Además cabe mencionar que en los cefalópodos existen reservas energéticas en órganos tales como el manto, los músculos y las vísceras (O'Dor & Wells, 1987; Moltschaniwskyj & Semmens, 2000 ) y que éstas están constituidas principalmente de proteínas y carbohidratos (Moltschaniwskyj & Semmens, 2000). ...
The objective of this study is to investigate to possible biological relationship among the reproductive process and the energy consumption from the digestive gland. 52 samples of the squid Loligo gahi were collected in bahía Concepción, between December of 2003 to February of 2004. For each sample mantle length were measured, and total weight, gonads and digestive gland were weighed. It were examined and determined the maturity stage of the gonads. Subsequently, it make calculations of the gonadosomatic and digestive gland index for each sample, later, to carry out correlations among both and with male individual's total weight and female separately. The male and females squids were not different in the proportion of individuals of different mantle length and maturity stage. In both sexes IGS increased in relation to maturity stage, but not IGD. The only significant correlation was in the males among the gonadosomático index with its total weight. The lack of correlations suggests that the digestive gland, would not have any important participation as storage organ and therefore in the energy consumption during the process of reproductive development. Apparently L. gahi can increases its feeding rate to replace the energy demand and of nutrients that it implies the gonadic development
... Female squid invests considerably more energy than males to deploy large accessory reproductive organs and vitellogenesis during the reproductive events (Stearns 1992). Thus, the energy used to reach sexual maturity comes from three primary sources: (1) the somatic tissue, (2) directly from food, and (3) as a combination of both processes (Arkhipkin 1993;Laptikhovsky and Nigmatullin 1993;Moltschaniwskyj and Semmens 2000). However, the high energetic cost applied during the reproduction indirectly causes decay of energy available for somatic repair (Roumbedakis and Guerra 2019). ...
... In accordance with Moltschaniwskyj and Semmens (2000), the energy invested by squid species (including L. diomedeae) for spawning comes from two principal sources: (1) food (60% Can. J. Zool. ...
Although the squid Lolliguncula diomedeae Hoyle, 1904 is of commercial and ecological importance in the Gulf of Tehuantepec (southeastern Mexico), this is the first study to examine female spawning strategy. Information on reproductive indicators was used to assess the impact of spawning behavior on growth rates and the condition of somatic tissue, since energy for reproduction is derived mainly from somatic tissue and from consumed food. Additionally, oocyte storage patterns were examined to determine the type of spawning that characterizes this species. A total of 1,347 females, ranging between 27.3 to 90.0 mm dorsal mantle length (ML) and 0.1 to 25.6 g of total weight, were examined. Statolith analysis indicates that the life cycle of L. diomedeae is 212 days. Allometric growth was observed during the female life cycle. The size at maturity was at 68.54 mm ML, with synchronous ovulation (by groups) and intermittent spawning. The results show that L. diomedeae is an energetically efficient squid species that feeds during all of its reproductive life stages, thus ensuring the occurrence of partial spawning events, and that feeding ends when senescence begins. However, its life cycle could be affected by the presence of coccidian parasites, mainly during senescence.
... Several researchers have pointed out the relationship between age, reproduction, maturity, somatic tissue, and resource availability (Pollero and Iribarne, 1988;Gabr et al., 1999a, b;Moltschaniwskyj and Semmens, 2000;Rosa et al., 2004Rosa et al., , 2005. It seems that for sexual maturation and egg production, octopus, cuttlefish, and squid use energy directly from food, rather than from stored products (Gabr et al., 1999a, b;Moltschaniwskyj and Semmens, 2000;Rosa et al., 2005;Otero et al., 2007). ...
... Several researchers have pointed out the relationship between age, reproduction, maturity, somatic tissue, and resource availability (Pollero and Iribarne, 1988;Gabr et al., 1999a, b;Moltschaniwskyj and Semmens, 2000;Rosa et al., 2004Rosa et al., , 2005. It seems that for sexual maturation and egg production, octopus, cuttlefish, and squid use energy directly from food, rather than from stored products (Gabr et al., 1999a, b;Moltschaniwskyj and Semmens, 2000;Rosa et al., 2005;Otero et al., 2007). In this context, Boyle and Knobloch (1984a, b) suggested that culture conditions could increase gonad growth in small-sized animals exposed to high temperatures, low food supply, or conditions where growth rates are low, because animals in such conditions are forced into maturity when they reach the "reproductive age," regardless of size. ...
Gonad development during the early life of Octopus maya is described in terms of histological, morphometric, oocytes growth, and somatic-oocyte relationship data obtained from octopus cultured at the UMDI-UNAM, in Sisal, Yucatan, Mexico. This study is the first publication on gonad development during the early life of Octopus maya. A total of 83 O. maya specimens were used; their sizes ranged from 6.5 to 76 mm of total length (TL), 4 to 28 mm of dorsal mantle length (DML), 2.5 to 20 mm of ventral mantle length (VML), and 0.0180 to 7.2940 g of fixed body weight (fBW). Animals were weighed and measured only after preservation. A loss of 10% of living weight was estimated for juvenile octopuses after formalin preservation. The relation of length to weight (VML, DML, TL/fBW) pooled for both sexes had a strong positive correlation (r), as shown by a potential power function that was quite close to 1. Compound images were produced from numerous microscopic fields. The histological examination revealed that, 4 months after hatching, male octopus (24.5 mm DML and 7.2940 g fBW) were in gonad stages 2 (maturing) to 3 (mature), with spermatogonia and spermatocytes in the tubule wall and abundant spermatids and spermatozoa in the central lumen of the seminiferous tubules, suggesting the occurrence of different phases of gonad development at different maturity stages. In contrast, females (22.5 mm DML and 4.8210 g fBW) at the same time since hatching were immature (stage 1), with many oogonia, few oocytes, and germinal epithelium. This suggests that males reach maturity earlier than females, indicating a probable onset of maturity for males at around 4 months of culture or 8 g of wet body weight. Our results indicate the possibility that the size-at-weight can be recognized early with a degree of certainty that allows the sexes to be separated for culture purposes; but more detailed studies on reproduction in relation to endocrinology and nutrition are needed.
... negative standardized residuals) were in poorer reproductive condition than individuals whose organs that were heavier than the predicted weight (i.e. positive standardized residuals) (Moltschaniwskyj and Semmens, 2000). Due to the nature of the fishing activity the structure of the dataset was not fully orthogonal; collections from Victoria were made from all 10 combinations of season and year, but collections from GAB were only from five of the year-season combinations (Table 3.1). ...
... negative standardized residuals) organ weight are suggested to be in poorer reproductive condition than organs that are greater than the predicted weight (i.e. positive standardized residuals) (Moltschaniwskyj and Semmens, 2000). Reproductive condition was analysed using a full three-way analysis of variance (ANOVA) to explore the effects of year, season and location, as well as their two and three way interaction on the mean standardized residuals calculated for each sex. ...
... Cephalopods have a large amino acid requirement for maintaining optimal growth and to supply the fuel for energy (Lee, 1994), and direct use of protein as energy reserve may account for the lack of major glycogen and lipid reserves in cephalopod tissues ( Storey and Storey, 1983;O'Dor et al., 1984). Although there is no evidence that the digestive gland provides stored energy for gonad development ( Gabr et al., 1999), the lipids in the digestive gland are possible substrates and site for energy storage in cephalopods (Moltschaniwskyj and Semmens, 2000;Phillips et al., 2001;Semmens, 2002). ...
... It seems that both Eledone species use energy for egg production directly from food, rather than from stored products. This direct acquisition was also proposed by other authors for temperate (Guerra and Castro, 1994;Collins et al., 1995) and tropical squids (Moltschaniwskyj and Semmens, 2000) and cuttlefishes ( Gabr et al., 1999). Polar lipids play important role in gametes (Pollero and Iribarne, 1988), because they are probably involved in the synthesis of the vitellus, a yolk phospholipoprotein (Fujii, 1960). ...
The effect of spermatogenesis and oogenesis on protein, lipid, glycogen, cholesterol and energy contents, total amino acid and fatty acid profiles of Eledone cirrhosa and Eledone moschata tissues (gonad, digestive gland and muscle) was investigated. A significant (p<0.05) increase in the amino acids and protein content of the gonad throughout sexual maturation (namely in oogenesis) was observed, but the allocation of these nitrogen compounds from the digestive gland and muscle was not evident. The major essential amino acids (EAA) in the three tissues were leucine, lysine and arginine. The major nonessential amino acids (NEAA) were glutamic acid, aspartic acid and alanine. A significant increase in lipid and fatty acid contents of gonad and digestive gland was observed. There was also little evidence of accumulated lipid storage reserves being used for egg production. It seems that for egg production Eledone species use energy directly from food, rather than from stored products. Most of saturated fatty acid (SFA) content of the three tissues was presented as 16:0 and 18:0, monounsaturated fatty acid (MUFA) content as 18:1 and 20:1 and polyunsaturated fatty acid (PUFA) content as 20:4n-6, 20:5n-3 and 22:6n-3. Cholesterol and glycogen contents significantly increased in gonad and digestive gland throughout maturation while the muscle revealed no obvious pattern. If Eledone's component sterols are of a dietary origin, a considerable variation in the cholesterol content between species might be expected on the basis of the sterol composition of their prey. Although spermatogenesis and oogenesis had a significant effect (p<0.05) in gonad and digestive gland energy content, the biochemical composition of digestive gland and muscle may not be primarily influenced by sexual maturation, but rather by other biotic factors such as feeding activity, food availability, spawning and brooding.
... The biochemical composition of cephalopods has been studied in a number of species inhabiting both coastal or oceanic waters and originating from tropical, temperate or polar environments (Takahashi, 1960;Jangaard and Ackman, 1965;Koning, 1972Koning, , 1993Hochachka et al., 1975;O'Dor et al., 1984;Kariya et al., 1986;Pollero andIribarne, 1988, Clarke et al., 1994;Pierce et al., 1999;Moltschaniwskyj and Semmens, 2000). These studies provide information at several levels: they can explain the nature and the role of the tissues and cells which compose them and they can be used to calculate energy allocation in body components or the energetic biomass of the populations. ...
... The lipid content also exhibited significant seasonal variation, attaining the highest values in May, which suggests that the lipid levels could be related to oogenesis and spermatogenesis. Similar results were obtained by Takahashi (1960) with Todarodes pacificus and Moltschaniwskyj and Semmens (2000) with Photololigo sp. Both studies showed that lipid levels fall precipitously with spawning and build up again thereafter. ...
The aim of this work was to investigate biochemical changes during the reproductive cycle of the common octopus, Octopus vulgaris, Cuvier, 1797. Proximate composition, fatty acids, cholesterol and amino acids were determined monthly in the mantle of O. vulgaris caught off in three different areas of the Portuguese coast. The moisture content exhibited significant seasonal and spatial variations, with a maximum value in Viana do Castelo in April (81.4%) and a minimum value in Tavira in October (76.5%); the mineral content tended to be similar to the results of other studies (1.4-1.9%). Nitrogen compounds were the major organic compounds (16.1-20.7%) and seem to be the most important energetic fuel in sexual maturation, spawning and brooding. In fact, the maturation of gonads and periods of feed deprivation (during brooding) can result in tissue depletion with marked decreases in the content of protein in muscle. With the profiles of SDS-PAGE it can be speculated that the exhaustion of these energetic sources, at the end of the reproductive cycle, might be explained by the decrease of the major myofibrillar proteins content (paramyosin, myosin and actin), due to the enhancement of the protease activity in the muscle. Glutamic acid (2.1-2.7 g 100 g−1), aspartic acid (1.4-1.9 g 100 g−1 wet weight) and leucine (1.3-1.8 g 100 g−1 wet weight) were found to be the major components within muscle proteins. The total lipid content (0.1-0.6%) and the major polyunsaturated fatty acids DHA (C22:6w3) and EPA (C20:5w3) showed variations which could be related to oogenesis and spermatogenesis. The cholesterol content can be correlated with the rapid maturation process, because the production of sexual hormones are related with the cholesterol metabolism. Some data of metabolic state, sexual maturation and reproduction, related with the biochemical composition of Octopus vulgaris, are certainly important to a better knowledge of octopus life-cycle.
... For example, little evidence of mobilisation of energy from the digestive gland was found during the reproductive development of Photololigo sp. (Moltschaniwskyj and Semmens, 2000); whereas there seems to be an energy tradeoff between somatic and gonadal tissues during maturation of Nototodarus gouldi (McGrath Steer and Jackson, 2004). In other species, such us Sepioteuthis australis, the level of reproductive investment in females may be related to temperature . ...
... These results are in agreement with those obtained by Rosa et al. (2004) for O. vulgaris and O. defilippi. The direct acquisition of energy for reproduction was proposed for other cephalopod species (Guerra and Castro, 1994;Moltschaniwskyj and Semmens, 2000;Smith et al., 2005); although strategies that channel stored products to reproduction have also been described (McGrath Steer and Jackson, 2004). O. vulgaris females seem to drive most of its energy acquisition from food resources to somatic growth until they reach a critical size (presumably near the size-at-maturity, and controlled by sex-dependent internal factors- Wells and Clarke (1996) postulated that Octopus gonadal growth is linked with an increase in the concentration of many amino acids and proteins in the urine). ...
Reproductive and energy allocation analyses were performed on 1418 common octopus (Octopus vulgaris) from the Galician creel fishery (NE Atlantic) between May 2000 and December 2005. Individuals ranged from 8 to 35 cm dorsal mantle length (DML) and 136–6303 g body weight (BW). The length–weight relationship for whole animals was BW = 2.9(±1.1) × DML2.17(±0.04) (r = 0.86; P < 0.00001). The sex ratio only differed from 1:1 during May and September. Spawning of O. vulgaris in this area extends from December to September with a unique peak in spring months. Size-at-maturity was 1788 g for females (n = 508); and 903 g for males (n = 467). Mean (±S.D.) potential fecundity was estimated at 221,447 ± 116,031 oocytes and mean oocyte length at 3.0 ± 0.8 mm. The mean number of fully developed spermatophores was 182 ± 88 with mean length of 48.8 ± 10.6 mm. Potential fecundity was significantly correlated with length and weight in both sexes. The condition (digestive gland to body weight ratio) of females increased proportionally with maturity stage and mature individuals had higher gonad investment suggesting that energy for gonad growth was derived from the diet rather than endogenous reserves. On the other hand, mature males showed poorer condition. The general picture of the reproductive biology of this species in Galician waters is discussed taking into account the seasonal wind-driven upwelling that governs this ecosystem.
... Although there was no significant difference in GSI among seasonal spawners from Taiwan (in contrast to females from Japan), a positive correlation (but no tradeoff) was found between somatic and gonadal investment in Taiwanese females. This pattern is similar to that of S. australis (Pecl and Moltschaniwskyj 2006), with energy for reproduction predominantly sourced from food rather than from stored somatic energy as in many loliginid species (Moltschaniwskyj and Semmens 2000;Pecl et al. 2004b). Thus, food availability might greatly affect energy allocation in Taiwanese females. ...
Swordtip squid Uroteuthis edulis is a commercially important species in coastal waters throughout the Northwestern Pacific, including those of Japan and Taiwan. Despite the importance of U. edulis to fisheries, previous studies on the life history traits (growth rate, size at maturity, and fecundity) of its populations in the Northwestern Pacific have been localized and region specific. Thus, we report life history traits of female swordtip squid from the waters off southern Japan and northern Taiwan, to identify seasonal variations within each population, as well as geographical variations between them. Variations in life history traits, including growth rate, mantle length (ML) at maturity, and female reproductive traits (gonadosomatic index, fecundity and egg size), are described and recognized to vary seasonally in both populations. Winter spawners in Japan have the highest growth rate, followed by spring spawners and summer spawners. Spring spawners in Taiwan mature at a younger age than autumn spawners. Geographical variations between populations are reported: fecundity level and egg size of spring spawners in Japan differ from those of spring and autumn spawners in Taiwan, but those of summer spawners in Japan are similar to those of spring and autumn spawners in Taiwan. Data on seasonal and geographical variations in life history traits of U. edulis are useful for effective squid fisheries management.
... A length-weight relationship (log(Weight) = log(CL)) was fitted to CL and weight (g) data for surviving prawns using ordinary least squares regression. This relationship was used to derive a condition index by calculating the residuals for each data point (after Moltschaniwskyj and Semmens 2000) and averaging across individuals in each tank. Following inspection of the data, survival was modelled against salinity according to Survival = β + β 1 log(Salinity). ...
Variation in salinity is one of the principal changes in estuarine physicochemistry that can impact the productivity of estuarine species. The effect of salinity on the mortality, growth, and metabolite profiles of juvenile Eastern School Prawn (Metapenaeus macleayi) was evaluated across a salinity gradient ranging from 0.2–36 over 60 days. Survival was >70% for salinity treatments other than the lowest salinity. Survival was 0% in the lowest salinity and all prawns had died within 3 days. Salinity did not appear to impact relative growth across the range of salinities examined. In contrast, relative somatic condition was greater at lower salinities and was negatively correlated with salinity, indicating lower salinities promote enhanced somatic condition in School Prawn. Total fatty acid concentration showed no relationship with salinity or somatic condition index. However, total fatty acid concentration did have a significant positive relationship with total amino acid concentration. Total amino acid concentration showed no linear relationship with salinity or somatic condition index. Quantitative profiling of individual fatty acids and amino acids showed some changes in response to salinity. Alpha-aminoadipic acid showed a significant positive relationship with salinity. These complex patterns suggest several shifts in cellular chemistry may occur throughout the salinity range investigated, potentially with metabolic consequences. These results highlight the complex responses of estuarine crustaceans to changes in salinity.
... Standardised residuals from the log CL log dry weight data was used as a size-independent measure of the somatic condition of an individual at the whole animal level (e.g. Moltschaniwskyj and Semmens, 2000). The splines were based on thin plate smoothing terms with default settings (Wood, 2003) applied to each variable, using the mgcv package (Wood, 2011) in R v. 3.2.0 ...
Habitat – Fishery Linkages and implications for Habitat Repair
... Energy for production of reproductive organs appears to be derived from diet rather than a stored energy source, given the gradual decline of the DGI with size. An obvious drop would suggest that lipid deposits within the digestive gland are being used as an energy source at the onset of reproductive maturation (Guerra and Castro 1994;Moltschaniwskyj and Semmens 2000). ...
Cephalopod populations exhibit high variability in life history characteristics, such as longevity and size-at-age. The aim of this study was to understand how characteristics of a newly described ‘superbull’ male morph in Doryteuthis gahi populations (Patagonian Shelf) arise and whether there is a selective advantage. At the population level, it is speculated that superbulls provide temporal and spatial connectivity, but individual benefit is less obvious. Age structure and reproductive potential of males was investigated to determine whether superbulls could provide connectivity. Environmental variables affecting size-at-age were explored to ascertain whether morphological differences were primarily phenotypically driven. Superbulls from the autumn spawning cohort were significantly older than the residual population, with added longevity potentially leading to spawning with the following cohort. A reduction in relative testis weight was apparent in superbulls, but spermatophore production remained high. Generalised additive mixed models indicated temperature, location and hatch year had significant effects on size-at-age. Weak correlations between warm El Niño–Southern Oscillation phases and superbull abundance were found. The results suggest that superbulls provide temporal connectivity and arise through phenotypic plasticity, likely providing connectivity as a side effect of body shape and size rather than a genetically selected advantage.
... Initially, spatial patterns in the abundance of School Prawn in the two lake systems were visualised by conducting Global Polynomial Interpolation in ArcGIS v 10.3 (ESRI). The relative condition of prawns in each of the two lake systems was assessed by calculating the standardised residuals from the relationship between log(Carapace Length) and log(Weight), which provided a size-independent measure of the somatic condition of an individual (Moltschaniwskyj and Semmens, 2000). To evaluate the potential impact of dissolved oxygen levels on relative condition, data were grouped for whether dissolved oxygen (logger measurements) dropped below 3 mg L −1 during the month (classified as ''critical'', or < 3 mg L −1 ) prior to capture, and compared with other samples (classified as ''normal'', or ≥ 3 mg L −1 ) for Watson-Taylor Lake and Queens Lake using a two-factor ANOVA. ...
Many factors can affect growth, survival, reproduction, and fisheries productivity of estuarine species, including structural and physico-chemical habitats, and freshwater inflow to estuaries. Land-based activities can lead to poor catchment condition, and catchment-derived stressors can adversely impact estuarine systems. Using the Eastern School Prawn (Metapenaeus macleayi) in a south-eastern Australian estuary (Camden Haven Estuary) as a case study, we examine juvenile recruitment and fisheries productivity alongside a comprehensive suite of catchment-derived stressors, and interpret patterns in the context of existing studies of lethal and sub-lethal impacts of these stressors on penaeid prawns. Logged dissolved oxygen data indicated a moderate frequency of hypoxia throughout the system, with occasional periods of anoxia. Dissolved aluminium concentrations remained above the relevant marine water quality guideline for the majority of the study period, and concentrations tended to correlate with estuarine inflow. Hypoxia led to depressed prawn abundance, and both hypoxia and high estuary inflow led to decreased somatic condition in prawns. Long-term commercial catch negatively correlated with estuary inflow, which was the opposite of the expected pattern for the species. These patterns highlight the potential cumulative impacts of a complex array of catchment-derived stressors on an important exploited penaeid species. Similar patterns probably occur for prawn species across other floodplain estuaries across south-eastern Australia, and suggest a hitherto unquantified economic impact of degraded catchments through losses in fisheries productivity.
... Standardised residuals from the log CL-log dry-weight data were used as a size-independent measure of the somatic condition of an individual at the whole animal level (e.g. Moltschaniwskyj & Semmens, 2000). The splines were based on thin plate smoothing terms with default settings (Wood, 2003) applied to each variable using the mgcv package (Wood, 2011) It should be noted that the rate of salinity decline and the endpoint salinity were correlated. ...
Estuaries act as nurseries for many penaeid prawns, but these habitats are highly susceptible to salinity decline through flooding. The rate of salinity decline and duration of exposure to non-optimal salinity may affect survival and subsequent recruitment of prawns to the fishery. This study aimed to determine the effect of salinity fluctuations observed in local estuaries during flood events using a novel dilution approach. Mortality of juvenile Melicertus plebejus (Hess) was assessed after 24 hr exposure to 24 rates of salinity decline ranging from 0.01% to 20% per hr. After the salinity decline, prawns were held at the final salinities for five days before again assessing mortality as well as aerobic metabolic rate and prawn water content. Salinity decline from 36 to ~0.8 led to 50% mortality, but continued exposure to low salinity for five days increased mortality at this salinity to 99% and shifted the 50% mortality point to salinity ~5. Aerobic metabolic rate and water content data suggested the cause of mortality due to exposure to salinities < 5 was osmoregulatory failure. Rapid salinity declines over 24 hr and sustained low salinity due to flooding could compromise the survival of juvenile prawns, potentially reducing recruitment to the fishery.
... The wet weight of each isopod was also measured. Gonads and livers were fixed in a mixture of 10ml 37% formaldehyde, 5 ml glacial acetic acid, 1.3g calcium chloride dihydrate and 85 ml distilled water (FAAC) for 4-6 weeks (Moltschaniwskyj and Semmens, 2000). ...
A thesis submitted for the degree of Master of Philosophy at The University of Queensland in August 2005.
... The low lipid content of S. apama (Table 4.2) is a feature of cephalopods, reported as <2% in several studies including Saavedra (1949), Pandit and Magar (1972), Cooper (1979), Coppini (1972), Sidwell and Ambrose (1975), Prince (1982, 1996), Cherel and Klages (1998), Goodman-Lowe et al. (1999), Moltschaniwskuj and Semmens (2000), Lozano et al. (2001) and Phillips et al. (2003). Crude protein values are based on the nitrogen content multiplied by the constant 6.25, a value used traditionally by national food quality regulatory bodies. ...
PhD thesis - Energetics and morphometrics of non-breeding albatrosses. Includes unpublished studies of basal metabolic rate and organ and muscle scaling of several albatross and petrel species
... The ova (fecundity) in parasitised and unparasitised female fish and the eggs in mouthbrooding males were counted by distributing them evenly in a 14 cm Petri dish divided into 1 cm quadrants, and counting them under a dissecting microscope. Gonads and livers were fixed in a mixture of 10 ml 37% formaldehyde, 5 ml glacial acetic acid, 1.3 g calcium chloride dihydrate and 85 ml distilled water (FAAC) for 4-6 weeks (Moltschaniwskyj and Semmens, 2000). To determine the developmental stage and ovum diameter, ovaries from parasitised and unparasitised females and eggs from the mouthbroods of males were dehydrated, embedded in paraffin and sectioned at 5 lm with a microtome. ...
Parasitic castration, the specific blocking of host reproductive output by an individual parasite, is a host– parasite interaction common to many invertebrates, particularly crustaceans, echinoderms and molluscs. It can reduce host density, alter host population dynamics and the evolution of host life history traits. Here we show that parasitisation by a single female cymothoid isopod, Anilocra apogonae, castrates its vertebrate host, the five-lined cardinalfish, Cheilodipterus quinquelineatus. Parasitised male fish fail to mouthbrood their young. The gonads of parasitised fish are smaller and parasitised female fish have substantially fewer and smaller ova than do the gonads of unparasitised fish. As for parasitic castrators of invertebrate hosts, A. apogonae on C. quinquelineatus are uniformly dispersed amongst infested hosts (one adult female isopod per host), are site specific, and their body size is highly correlated with that of their host. These isopods are large relative to the body size of their hosts, averaging 3.8% of the weight of the host. Parasitised fish also weigh less and are shorter than unparasitised fish of the same age. Despite the presence of other potential hosts, A. apogonae only infests C. quinquelineatus. The consistency of the ecological correlates amongst known parasitic castrators suggests that the parasitic castrator host– parasite relationship will be recognised for other parasites of vertebrates.
... An efficiency of 14% in the first week might be low, but 102% at 18 months is definitely too high! Cephalopods can lose weight during spawning (Moltschaniwskyj and Semmens 2000, Jackson 2000) so this may reflect over-extrapolation of the ...
The term 'growth model' in fisheries literature commonly refers to equations predicting size-at-age. Applying statistical goodness-of-fit criteria to such equations measures their capacity to describe populations but implies an unstated corollary that some individuals grow 'wrong'. This 'wrongness' may result from techniques misrepresenting age, but, as cephalopods often exhibit ten-fold variation in growth under controlled conditions and have multiple sub-annual cohorts in nature, it may simply be wrong to try to represent a 'population' with a single equation. This article provides a simple spreadsheet model, adjustable daily, that allows tests of a wide variety of environmental and physiological variables' effects on an individual animal's growth parameters. This allows independent elimination of implausible individual errors from statistical analyses and has important consequences for growth models used in an ecosystem context. Growth efficiency during low food intake can be ten-fold lower than at high intakes, so the cumulative error in estimating a population's energetic impact on an ecosystem may be wrong by a hundred-fold. The standard assumptions of this spreadsheet model can be run with no input except size and age, but all assumptions, except that energy can be created or destroyed, can be adjusted, if real measurements such as temperature or feeding rate are available.
... This is evident at the cellular level, with squid growing over their entire lifespan by both hypertrophy (increased muscle size) and hyperplasia (addition of new muscle fibres, Moltschaniwskyj 1994, Pecl & Moltschaniwskyj 1999, while teleost fish generally cease hyperplasia with age (Jackson & O'Dor 2001). Squid have exceptionally high growth efficiency, with a protein-based metabolism that rapidly converts energy into growth rather than storage (O'Dor & Webber 1986, Lee 1994, Moltschaniwskyj & Semmens 2000. The metabolic and growth rates of squid are indeed higher than many poikilothermic vertebrates, including most teleost fish, and can in fact be as high as some mammals (Pörtner & Zielinski 1998, Zielinski & Pörtner 2000. ...
... However, there are differences in the evolution of the DGI between regions, that suggest that the individual spawning period may be longer in southern Brazil: in northern Patagonia, the DGI decreases along sexual maturation and can be associated to intense reserve mobilization along a short spawning season (Pujals, 1982;Iribarne, 1991); in southern Brazil, the DGI remains high along maturation, suggesting accumulation of reserves for a longer period of spawning and parental care of the eggs. However, it is not consensual that the digestive gland has an important role in energy storage in cephalopods, as many authors also consider the reserves in the muscle and gonads (Moltchaniwskyj and Semmens, 2000;Rosa et al., 2004;Semmens et al., 2004). ...
Octopus tehuelchus is a small octopus endemic to subtropical and temperate waters of the southwestern Atlantic continental shelf. Its reproductive biology was studied by examining 319 individuals, measuring 20 to 79 mm mantle length (ML), col-lected between 1979 and 2009 along the coast of southern Brazil. Females are more numerous in shallower waters and attain larger size than males. Fully mature males and females were observed in all seasons and mean mantle length at matu-rity was 46 mm for females and 27 mm for males. The number of intraovaric oocytes of maturing females ranged from 20 to 448 and was positively correlated with female size. In mature females, a wide range of intraovaric oocytes diameters was observed, in some cases with a bimodal distribution. The num-ber of eggs in the four layings ranged from 86 to 237, the diameters ranged from 8.2 to 14.5 mm and no bimodality was observed. Digestive gland grew proportionally to body weight along maturation in females but not in males, suggesting accu-mulation of reserves for spawning and parental care in females and priority for sexual maturation over growth in males. The comparison of the reproductive cycle of O. tehuelchus in south-ern Brazil with populations from northern Patagonia shows that the species has the potential for year round spawning, but ecological constrains only allows it to express this potential in the lower latitudes of its distribution.
... Residuals were standardized by dividing each residual by the standard deviation of the predicted values. According to Moltschaniwskyj and Semmens (2000) residuals of the weight-length relationship provide a size-independent measure of the somatic condition of an individual at the whole animal level. An individual that is lighter for its length than predicted from the regression equation (negative residual), is suggested to be in poorer somatic condition than an individual who is heavier for its length than predicted from the regression equation. ...
El N no and La N na event Perú a b s t r a c t Based on size at maturity and standardized residuals from mantle length (ML)–total weight (TW) and mantle length–gonad weight (GW) relationships, this paper describes the interannual variability of the size at maturity (SM), somatic and reproductive investment of mature males and females of Dosidicus gigas during the spawning peak (October–March) for the period 1994–2006 in the Northern Humboldt Current Ecosystem (Peruvian waters). Significant changes occurred in the SM in females as well in males: before 2001 the average did not exceed 47 cm ML, while from 2001 onwards the average MS varied between 62 and 96 cm ML. The average SM was generally higher in females. There was a great individual variability of somatic and reproductive investment, being higher in large-sized mature squids. No relationship was found between SM and somatic condition. The presence of small-sized mature squids in good somatic condition under different scenarios of sea surface temperature (normal, warm or cold periods; El N no and La N na events) does not indicate a relationship between somatic condition and SST. The relationship between reproductive and somatic investment was variable and independent of the sex. It also varied among different years. This would indicate that females and males may respond differently under the same environmental conditions. Considering the relationship between fecundity and ML, mature females at larger sizes had a lower reproductive condition, but also a higher potential fecundity. Lower fertility potential for some small mature females is offset by greater investment in reproduction, particularly under adverse environmental conditions. The positive correlation between the abundance (CPUE) and SM shows that the biomass was greater in periods dominated by the presence of large-sized mature squid.
... Water (73 to 87%) and protein (8 to 20%) represent the primary components of cephalopod bodies, which yield estimates of 4 to 10% C and 2 to 4% N relative to WW (Croxall & Prince 1982, Krzynowek & Murphy 1987, Moltschaniwskyj & Semmens 2000 ). In comparison , Stauroteuthis syrtensis were composed of > 90% water, 3 to 7% C, and 0.6 to 1.4% N. In addition, the chemical composition of S. syrtensis was more similar to values reported for various gelatinous zooplankton than to values reported for crustaceans or fishes (Bailey et al. 1995). ...
The cirrate octopod Stauroteuthis syrtensis is a mesopelagic species commonly collected in the North Atlantic. Individuals were observed at depths > 600 m and typically within 100 m of the bottom in three similar to 900 m deep canyons indenting the southern edge of Georges Bank. When first sighted, most octopods were floating passively with their webbed arms gathered into a small ball. When disturbed, they expanded their webs to form a 'balloon' shape, swam slowly by Sculling their fins, pulsed their webs like medusae and, in some cases, streamlined their arms and webs and moved away smoothly by rapidly sculling their fins. The bodies of 9 octopods comprised 92 to 95 % water, with tissue containing 9 to 22 % carbon (C) and 2 to 4 % nitrogen (N). These values were similar to those reported for medusae and ctenophores. Oxygen (O(2)) consumption rates of 4.6 to 25.8 mu mol 02 g(-1) C h(-1) were within ranges reported for medusae, ctenophores, and deep-water cephalopods. The stomachs of S. syrtensis, dissected immediately after capture, contained only the calanoid copepod Calan us finmarchicus. Calculations indicated that S. syrtensis need 1.3 to 30.1 ind. d(-1) of C. finmarchicus to meet their measured metabolic demand. Excretion rates (0.3 to 12.4 mu g NH(4)(+) g(-1) C h(-1) and 0.06 to 4.83 mu g PO(4)(3-) g(-1) C h(-1)) were at least an order of magnitude lower than rates reported for other octopods or gelatinous zooplankters. O:N ratios (11 to 366) suggested that S. syrtensis catabolized lipids, which may be supplied by C. finmarchicus. Vertical distribution, relatively torpid behavior and low metabolic rates characterized S. syrtensis as a benthopelagic and relatively passive predator on copepods.
... Loliginids have been found to grow by both a combination of increase in fibre size (hypertrophy), along with continual recruitment of new muscle fibres (hyperplasia) (Moltschaniwskyj 1994;Preuss et al. 1997;Pecl and Moltschaniwskyj 1999;Ho et al. 2004). Maturity in some tropical species coincides with a detectible loss of condition and loss of large muscle fibres, although fuel for reproduction appears to come predominantly from feeding rather than from stored reserves (Moltschaniwskyj 1995;Semmens 1998;Moltschaniwskyj and Semmens 2000). Conversely, L. opalescens is a terminal spawner that displays a dramatic loss of tissue condition (Fields 1965). ...
Recent years have seen the emergence of extensive studies of myopsid squid growth of the family Loliginidae. This has greatly advanced our understanding of their life histories. Growth data have accumulated from both statolith-based field studies and culture work. Validation studies on loliginids continue to support that statolith increments are laid down daily. Ageing work has also revealed that short lifespans are typical, with nine of the 21 species studied having lifespans <200 days, eight species with lifespans between 200 days and about 1 year and only three species with lifespans >1 year. While growth is continuous and non-asymptotic, the marked plasticity in size-at-age has hindered the development of a general model to describe squid growth. Many loliginids are multiple spawners that continue to feed while growing and reproducing, although there has been some documented loss of conditon in mature individuals. An exception is Loligo opalescens, which has a terminal spawning strategy with a marked loss of condition and post-spawning mortality. Quantification of the cost of living and the energetics of loliginids are likely to be best achieved by combining field and culture studies on a species such as the Indo-Pacific squid Sepioteuthis lessoniana.
... Residuals were standardized by dividing each residual by the standard deviation of the predicted values. According to Moltschaniwskyj and Semmens (2000) residuals of the weight-length relationship provide a size-independent measure of the somatic condition of an individual at the whole animal level. An individual that is lighter for its length than predicted from the regression equation (negative residual), is suggested to be in poorer somatic condition than an individual who is heavier for its length than predicted from the regression equation. ...
Based on size at maturity and standardized residuals from mantle length (ML)–total weight (TW) and mantle length–gonad weight (GW) relationships, this paper describes the interannual variability of the size at maturity (SM), somatic and reproductive investment of mature males and females of Dosidicus gigas during the spawning peak (October–March) for the period 1994–2006 in the Northern Humboldt Current Ecosystem (Peruvian waters). Significant changes occurred in the SM in females as well in males: before 2001 the average did not exceed 47cm ML, while from 2001 onwards the average MS varied between 62 and 96cm ML. The average SM was generally higher in females. There was a great individual variability of somatic and reproductive investment, being higher in large-sized mature squids. No relationship was found between SM and somatic condition. The presence of small-sized mature squids in good somatic condition under different scenarios of sea surface temperature (normal, warm or cold periods; El Niño and La Niña events) does not indicate a relationship between somatic condition and SST. The relationship between reproductive and somatic investment was variable and independent of the sex. It also varied among different years. This would indicate that females and males may respond differently under the same environmental conditions. Considering the relationship between fecundity and ML, mature females at larger sizes had a lower reproductive condition, but also a higher potential fecundity. Lower fertility potential for some small mature females is offset by greater investment in reproduction, particularly under adverse environmental conditions. The positive correlation between the abundance (CPUE) and SM shows that the biomass was greater in periods dominated by the presence of large-sized mature squid.
... Overall, this study produced a model of protein turnover that indicates that when Euprymna tasmanica allocates energy to reproductive growth, there was no difference in retention of protein for somatic growth between mature and immature individuals . Significantly slower mean fractional rates of mantle protein degradation in mature females (this study) and no evidence that lipid is used as a storage product (Moltschaniwskyj and Johnston 2006 ) support an income energy model for reproduction in some cephalopod species (Hatfield et al. 1992; Moltschaniwskyj 1995; Moltschaniwskyj and Semmens 2000; Semmens and Moltschaniwskyj 2000). This study has revealed that both fractional rates of mantle protein synthesis and degradation were slower in mature individuals, suggesting that less energy is available for protein synthesis but slower rates of protein degradation allowed somatic growth to continue (Moltschaniwskyj and Carter 2010); this supports an adaptive response in mantle protein turnover (Hawkins 1991). ...
Abstract Sourcing energy for reproduction is a major driver of the life-history characteristics of animals. Unlike other molluscs, cephalopods do not appear to have significant glycogen stores, and energy is either sourced directly from ingested food or mobilized from protein stores in the muscle. Given the importance of protein to cephalopods, this study quantified changes in protein turnover in the muscle tissue in reproductively immature and maturing/mature individuals. Quantifying protein accretion and protein synthesis allowed an assessment of protein turnover in immature and maturing individuals of the southern dumpling squid (Euprymna tasmanica), which has fast nonasymptotic growth, has a short generation time, and does not use lipid stores. This study found that protein turnover slowed in the mantle muscle tissue with gonad growth, suggesting an adaptive response to the energy demands associated with reproduction but one that allows for continued somatic growth and muscle function in these animals. However, the cost of reproduction may be indirect, with less energy available for somatic repair, and therefore may be responsible for the rapid senescence typical of many cephalopod species.
... A decline in relative mass of the mantle during reproductive maturation was seen in Illex argentinus (Hatfield et al. 1992) and Photololigo sp. (Moltschaniwskyj and Semmens 2000), and a decline in growth rates was seen in Photololigo sp. (Moltschaniwskyj 1995). ...
Age and size-at-maturity of Loligo vulgaris from Portuguese waters were evaluated in order to explain its complex population structure, which is strongly influenced by continuous spawning. Age was obtained by increment counting in statoliths. Maturity ogives by age group indicated that males mature one month earlier (at 277 days) than females (at 298 days). Females mature at a ML50% of 17.6 cm, while males mature at smaller sizes. The later, however, showed a high degree of complexity in the size at maturity with evidence of two size at maturity groups. In both sexes, maturity was ultimately found to be primarily dependent on size rather than age. The effect of hatching season on age-at-maturity, size-at-maturity and reproductive investment was analysed by comparing two groups of squid hatched under distinct environmental conditions, namely the temperature during the first 3 months of life, the cold cohort (CC),
hatching between December and March and the warm cohort (WC), hatching between May and September. Significant differences were found between cohorts on age-at-maturity, size-at-maturity and reproductive investment, giving indication of the environmental influences on sexual maturity. CC squid mature ca. 2 months later in life than WC squid and at a significantly larger size. The reproductive nvestment as measured by GSI was higher in the WC squid. Much of the variability in age and size-at-maturity of females in the population was due to differences between cohorts but this was not the case for males.
... Similar results were obtained from cephalopods such as Todarodes pacificus (Takahashi 1960), Photloligo sp. (Moltschaniwskyj & Semmens 2000), R. macrosoma, (Rosa et al. 2006), and L. forbesi (Kilada & Riad 2008). These studies showed that lipid levels fell sharply with spawning and subsequently recovered. ...
The aim of this work was to investigate the seasonal variability in the biochemical composition in both sexes of Loligo forbesi, (Streenstrup 1856) in two locations in Egypt: the Mediterranean Sea off the coasts of Alexandria and north of the Gulf of Suez. The study is also aimed to document for the first time the fatty acids composition in both sexes in each location. There was a significant difference in the seasonal variations of total protein (P = 0.0001), total lipids (P = 0.036) and total carbohydrates (P = 0.009). Also, there was a significant difference in total lipids (P = 0.008) between sexes. Total lipids and protein declined from spring to summer and then increased in fall before they decrease again in the winter in males and females. Meanwhile, the concentration of total carbohydrates in females decreased from spring to fall then increased slightly in winter. There was a negative correlation between Gonado Somatic Index and Nidamental gland Somatic Index and each of total protein and lipids in different sexes (P = 0.01), which was not the case with total carbohydrates (P = 0.1). Seasonal fluctuations in biochemical content were attributable to the reproductive state of the animal. Although there was no significant difference in either total saturated lipids or total unsaturated lipids among the two sexes or between the two locations (P > 0.05), variations were observed in some fatty acids. The most predominant saturated fatty acid was palmitic acid (C16:0), comprising 68% to 73% for both sexes and locations. Most of the monounsaturated content was present as Cis-Pentadecanoic (C15:1) and palmiboleic (C16:1). Omega 3-poly-unsaturated fatty acids, which include linolenic, EPA, and DHA comprised 80% of total polyunsaturated fatty acids.
... The lack of major glycogen and lipid reserves in cephalopod tissues favours the direct use of protein as an energy supply in such marine species [23,34]. However, the results of the present study clearly indicate that the digestive gland exhibits a remarkably high lipid content which, according to previous research on other cephalopod species [35,36], might be employed as a metabolic substrate in common octopus. ...
Seasonal variation of octopus (Octopus vulgaris) lipid composition was investigated in four tissues: arm, mantle, ovary and digestive gland. A non-homogeneous fat distribution was observed, with the digestive gland exhibiting a higher (p <0.05) lipid content than the other tissues. The ovary showed a higher (p <0.05) fat content than both muscle tissues, reaching its highest (p <0.05) value in winter. Neutral lipids – free fatty acids (FFA), triacylglycerols, and sterols (ST) – exhibited their highest (p <0.05) concentrations in the digestive gland and their lowest (p <0.05) values in muscle tissues. The phospholipid (PL) content of the ovary was the highest (p <0.05) of all tissues analysed, with the PL content also being significantly (p <0.05) higher in the digestive gland than in arm and mantle. The concentrations of most lipid classes (FFA, PL and ST) exhibited a seasonal variation. The fatty acid composition showed a remarkable difference between the digestive gland and all other tissues analysed. Thus, the digestive gland exhibited higher (p <0.05) contents in monounsaturated fatty acids and also lower (p <0.05) contents in both saturated (SFA) and polyunsaturated (PUFA) fatty acids. The highest mean values in SFA and PUFA were observed in ovary and muscle tissues, respectively. A seasonal effect was observed for SFA and PUFA.
... The genotypic plasticity of this species allows individuals to adapt to the variable environmental conditions experienced over a vast distribution area, which covers a considerable latitudinal gradient. Animals from the colder range of the species are larger, mature later and possess a single and relatively restricted breeding season (Moreno et al., 2005), probably as consequences of a physiological limit to sexual maturation (Moltschaniwskyj and Semmens, 2000;Pecl and Moltschaniwskyj, 2006), the slow metabolism observed in colder waters and a predictable oceanographic regime. Animals from the semi-tropical non-upwelling oceanographic regimes in the species range, on the other hand, have a warm, less productive but predictable environment, in which all animals hatch to a relatively constant food supply, and are able to grow fast and mature early. ...
Loligo vulgaris is the most abundant and commercially important species of squid in Portuguese waters. The species presents a complex population structure due to a short life-cycle, highly variable growth rates and a long spawning period. The latter characteristics combined with the marked seasonality of the Portuguese coast results in individuals that are born in different seasons being influenced by different environmental conditions, notably water temperature, as has previously been shown.In the present study, we have taken animals belonging to each of two temperature-based hatching cohorts (cold and warm cohorts – CC and WC) and determined the fecundity and egg size of individuals on either one, in order to determine whether animals in different cohorts followed different reproductive strategies.Significant differences were found between the cohorts regarding reproductive investment, fecundity and size of oocytes. Individuals of the CC (larger and older when reaching maturity) had lower fecundity than individuals of the WC, but presented larger oocytes. WC females (smaller and younger at maturity) present higher fecundities and higher GSIs. Such differences further demonstrate the high plasticity and adaptability of these organisms to environmental conditions and highlight the advantage of integrating environmental variables in fisheries assessment.
... In contrast, no change in the lipid content of the digestive gland occurred during reproductive maturation in the Table 2 Average specific growth rates (percentage increase in body weight per day), and digestive gland % lipid dry weight, water, and adjusted digestive gland weight (g) in the two groups of males fed at different ration levels and the mysid shrimps that were used as the diet (Semmens 1998) and Photololigo sp. (Semmens 1998;Moltschaniwskyj and Semmens 2000). Likewise the role of the digestive gland in lipid storage appears to vary and is also not related to habit (Table 4). ...
The aims of this study were to assess quantitatively the enzymatic ability of squid to digest lipids and the ability of the digestive gland to accumulate lipid classes associated with storage. This was achieved through two manipulative experiments using the dumpling squid, Euprymna tasmanica. Firstly, we measured lipase activity and determined the presence and location of lipid vacuoles within the digestive gland; secondly we identified and quantified lipid classes in the digestive gland. Given the levels of lipase activity, we provided evidence for the first time that a squid species is capable of digesting lipid at levels comparable to invertebrates known to use dietary lipid. A poor relationship between feeding activity and lipase secretion suggests that enzyme production is continuous. The second experiment found no evidence that lipid was stored in the digestive gland; most of the lipid present in the gland was either structural or a dietary by-product. The implication of these findings is that for this species lipid is most probably being immediately digested and used for growth and reproduction rather than being stored in the digestive gland. We consider that the role and storage of lipid is likely to vary among different cephalopod species, but not predictably as function of their lifestyle. Therefore, potential locations for lipid storage, other than the digestive gland, need to be considered and using changes in the relative size of the digestive gland as a measure of condition needs to be interpreted with care.
... These somatic-and reproductive-condition residuals were standardised by dividing each residual by the standard deviation (SD) of the predicted values. Residuals of weight-length relationships provide a size-independent measure of the somatic or reproductive condition of an individual at the whole animal level (Moltschaniwskyj and Semmens 2000, Pecl et al. 2004a). Individuals with positive residual values have a greater reproductive investment or are in better somatic condition compared to the average population, whereas individuals with negative residuals are in lower reproductive condition or poorer somatic condition than the average population. ...
This study explored population dynamics of Sepioteuthis australis on a fine temporal scale before, during, and after a 3-month commercial fishing closure on the summer inshore spawning grounds of Great Oyster Bay, Tasmania, Australia. An abrupt change in male size (mantle length) and population sex ratio after the re-opening of the commercial fishery suggests that fishing alters the population structure on the spawning beds from a ‘natural’ structure which is highly biased towards males, to a more even ratio of males to females. Although jigs are taking a representative sample of the squid population using the spawning beds at any one time, the fishery is apparently still effectively selective for males, potentially as a function of differential spawning movements of the two sexes. Increased fishing pressure over the past 5years had been correlated with a change towards a highly male-biased sex ratio on the spawning beds; however the current study suggests that increased fishing pressure in recent years may not have reduced the proportion of females. Instead, the inter-annual change in sex ratio may reflect changes in the degree of protection from fishing, with progressively longer closures allowing time for more males to accumulate on the beds and therefore, for the proportion of males to increase (as opposed to a decrease of females). As fishing is selective for males, fishing throughout the spawning season could potentially modify the process of sexual selection and the mating behaviors of the individuals within the spawning population, highlighting the need for closures over this crucial period. Additionally, examinations and comparisons of squid population structure need to be interpreted in light of fishing pressure and broader movement patterns.
... The existence of an individual storage organ of cephalopods is still discussed and the capacity of the digestive gland to store energy in the form of lipids was generally accepted. However, a number of studies found no evidence for this (Semmens 1998Semmens , 2002 Moltschaniwskyj and Semmens 2000; Ibáñez et al. 2005 ) or found that the lipid metabolism of cephalopods is restricted (e.g. Phillips et al. 2001 Phillips et al. , 2002). ...
Cannibalism refers to the action of consuming a member of the same species and is common in many taxa. This paper reviews
the available literature on cannibalism in cephalopods. All species of the class Cephalopoda are predators and cannibalism
is common in most species whose diet has been studied. Cannibalism in cephalopods is density-dependent due to their aggressive
predatory and in case of the octopuses territorial nature. It also depends upon local and temporal food availability and of
the reproductive season. Cannibalistic behaviour is positively related to the size of both cannibal and victim. It can affect
population dynamics of cephalopods in periods of low food availability and/or high population abundance. Cephalopods are generally
restricted in their ability to store energy. It is thus assumed that cannibalism is part of a population energy storage strategy
enabling cephalopod populations to react to favourable and adverse environmental conditions by increasing and reducing their
number. Finally, we propose five orientation points for future research on cannibalism in cephalopods.
The Add-my-Pet (AmP) collection of data on energetics and Dynamic Energy Budget (DEB) parameters currently contains 92 of the 800 extant species of cephalopods. Growth data, as reconstructed from statolith-, beak- or shell-readings, show a rather large scatter, whereas that from laboratory specimens with known age, does not. This implies that food availability varies under field conditions and/or age-determination is uncertain. We compare DEB parameter values and traits of cephalopods with those of other molluscs (Polyplacophora, Bivalvia, and Gastropoda). All cephalopods appear to start accelerating their metabolism at birth, quite few even up till puberty. As a consequence, length-at-age initially shows a clear up-curving at constant temperature and food, which is not clearly linked to morphological changes. They have a high acceleration factor, specific somatic maintenance, surface area-specific assimilation and maximum reserve density. The energy conductance, which controls reserve mobilisation, is typical for molluscs, and age at death is low. The investment into reproduction, in terms of specific offspring mass production per life span, is typical for molluscs. The negative effects that a short life span would have on reproductive output is compensated by a large allocation fraction to maturation or reproduction. Mass at birth is larger than that of gastropods, which, in turn, is much larger than that of bivalves and polyplacophorans. Cephalopod reproduction in terms of number of offspring per life time is, therefore, smaller than that of other molluscs. Although cephalopods are reputed to grow fast, gastropods grow equally fast per gram at maximum rate, while bivalves and polyplacophorans grow quite a bit slower. We conclude that 79% of the cephalopod species do not survive thinning of their populations in the long run, while this holds for some 20% of other animal species. This underscores their vulnerability for this type of harvesting.
En el presente estudio se evaluó el efecto que tiene en el crecimiento y en el
acondicionamiento reproductivo la inclusión de ácidos grasos poliinsaturados a la
dieta de Octopus maya en condiciones de cultivo en colectivo e individual. Para
conocer la forma en que las condiciones de cultivo y la dieta alta en ácidos grados
poliinsaturados modulan el crecimiento de juveniles tempranos y pre–adultos de
O. maya se realizaron tres experimentos dirigidos a probar la relación entre ambas
variables: efecto de la individualización y el tipo de alimento en juveniles
tempranos, efecto de la individualización y el tipo de alimento en pre–adultos y
efecto del tipo de alimento en condiciones de cultivo en colectivo; realizándose
además un ensayo con hembras pre–adultas de O. maya para conocer si éstas
transfieren directamente los ácidos grasos de mayor importancia contenidos en el
alimento al vitelo de los huevos a medida que se aproxima el evento reproductivo.
Se observó que el crecimiento de los juveniles de O. maya es afectado por la
forma de cultivo. Animales mantenidos individualmente tuvieron un crecimiento
más lento (0.024 g por día) que el registrado en animales mantenidos en
estanques y en forma colectiva (0.054 g por día), reportándose un efecto
significativo de la dieta enriquecida con ácidos grasos poliinsaturados sobre el
crecimiento de los pre–adultos de O. maya. Estos resultados sugieren que sin
limitaciones de espacio los animales pudieran aprovechar los efectos benéficos de
la dieta lo que produciría un mayor crecimiento. También se observó que las
hembras pre–adultas de O. maya transfieren directamente del alimento los ácidos
grasos necesarios para la síntesis de vitelo, siendo los más frecuentes C14:0,
C16:0, C17:0, C18:0, C18:1, C20:1, C20:2, C20:3n–6, C20:4n–6 (AA), C20:5n–3
(EPA) y C22:6n–3 (DHA), constituyendo el 96 por ciento de los ésteres metílicos
de ácidos grasos, sugiriendo que su adición a la dieta podría mejorar la calidad de
los huevos.
The objective of this study is to investigate to possible biological relationship among the reproductive process and the energy consumption from the digestive gland. 52 samples of the squid Loligo gahi were collected in bahía Concepción, between December of 2003 to February of 2004. For each sample mantle length were measured, and total weight, gonads and digestive gland were weighed, It were examined and determined the maturity stage of the gonads. Subsequently, it make calculations of the gonadosomatic and digestive gland index for each sample, later, to carry out correlations among both and with male individual's total weight and female separately. The male and females squids were not different in the proportion of individuals of different mantle length and maturity stage. In both sexes IGS increased in relation to maturity stage, but not IGD. The only significant correlation was in the males among the gonadosomático index with its total weight. The lack of correlations suggests that the digestive gland, would not have any important participation as storage organ and therefore in the energy consumption during the process of reproductive development. Apparently L. gahi can increases its feeding rate to replace the energy demand and of nutrients that it implies the gonadic development.
The reproductive biology of the Panama brief squid was evaluated using reproductive indicators, and histological and histochemical analyses. A total of 2,460 squid were analyzed, which were captured during 15 exploratory fishing surveys in the Gulf of California during 2003 to 2006 and 2008. Of the total sample, 61% were female, 15% were male, and the rest were undifferentiated. Based on the frequency of the gonad developmental stages, the largest number of mature females was identified in February and October, whereas mature males were found in April and August. This result coincided with the gonadosomatic index. According to the histological analyses, we characterized 4 stages of oogenesis: previtellogenesis, vitellogenesis, postvitellogenesis with mature oocytes, and postspawning. We also characterized 6 substages of oocyte and 2 structural indicators of spawning: oogonia (Po0), previtellogenic oocyte primary (Po1), previtellogenic oocyte secondary (Po2), vitellogenic primary oocyte (Vo1), secondary vitellogenic oocyte (Vo2), postvitellogenic oocyte (Pvo), postovulatory follicles, and atresia. Oocyte size among types showed significant differences (P < 0.05). The presence of postovulatory follicles, and oocytes of different sizes and various developmental stages throughout the study period indicates that the Panama brief squid has a synchronous ovarian development with multiple spawning. The size at first maturity (L-50) indicates that males (mantle length, 51 mm) mature at lengths shorter than females (mantle length, 85 mm).
This study investigates for the first time the reproduction biology of Uroteuthis duvauceli in the northern Red Sea, Egypt, over 4 seasons. The sexual maturity was analyzed using the gonad condition in both sexes and by the color of the accessory nidamental glands in females. Spawning season was determined by calculating the gonadosomatic index (GSI) in both sexes as well as the nidamental gland—somatic index in females. Results showed that the spawning season is in winter and early spring. Lastly, the biochemical composition of the mantle in males and females was estimated in the 4 seasons. Lipids, protein, and carbohydrates had a significant difference between the 2 sexes (P < 0.05); however, only protein differed significantly between the 4 seasons (P < 0.05). The seasonal fluctuation of GSI showed a similar trend to the seasonal variation in various biochemical components. In addition to the total lipids and proteins, detailed profiles of each biochemical component are discussed in relation to the sexual maturity of the animal. Also, the morphometric characteristics of males and females of the squid U. duvauceli were investigated. Various body parts were found to have significant difference between the 2 sexes over the 4 seasons (P < 0.01). The analysis also showed that total length has a significant difference in relation to the mantle length between the 2 sexes (P = 0.016). The analysis of length frequency of male and female samples revealed the presence of 2 modes that are assumed to be 2 y classes.
The aim of this study was to investigate the biochemical changes that occur during sexual maturation of the squids Illex coindetii and Todaropsis eblanae. In both species, amino acids and protein content increased in the gonad throughout maturation, but the allocation of these nitrogen compounds from the digestive gland and muscle was not evident. A significant (P 0.05) increase in the content of lipids and fatty acids was observed in the gonad and digestive gland. It seems that both species take energy for egg production directly from food, rather than from stored products. Analyses for cholesterol revealed a signif- icant (P 0.05) increase in the gonad, and the lipid content differences between species are potentially related to differ- ent feeding ecologies. The glycogen reserves in the gonad increased significantly (P 0.05), suggesting that glycogen has an important role in the maturation process. It was evident that sexual maturation had a significant effect upon the gonad energy content, but because the energy variation in the digestive gland and muscle was nonsignificant (P 0.05), there was no evidence that storage reserves are trans- ferred from tissue to tissue.
We develop a per-recruit model for the management of the California market squid (Loligo opalescens) fishery. Based on recent confirmation of determinate fecundity in this species, we describe how catch fecundity (i.e., eggs remaining in the reproductive tracts of harvested females) can be used to simultaneously infer fishing mortality rate along with management reference points such as yield-per-recruit, spawned eggs-per-recruit, and proportional egg escapement. Rates of mortality and egg laying have important effects on these reference points. Somewhat surprisingly, increasing the rate of natural mortality decreased spawned eggs-per-recruit while increasing proportional egg escapement. Increasing the rate of egg laying increased both spawned eggs-per-recruit and egg escapement. Other parameters, such as the maturation rate and gear vulnerability of immature females, affected the reference points. In actual practice, the influence of these parameters for immature squid may go undetected if immature squid are excluded from analysis of the catch. Application of this model to routine management is feasible but requires refinement of sampling procedures, biological assumptions, and model parameters. This model is useful because it is grounded on empirical data collected relatively inexpensively from catch samples (catch fecundity) while allowing for the simultaneous calculation of instantaneous fishing mortality rate and egg escapement.
Many cephalopods are 'multiple spawners'; however, we know little about the timing and dynamics of egg production. This has implications for the allocation of energy to reproduction, lifetime fecundity and subsequent recruitment. The current study aimed to determine if Sepioteuthis australis (Quoy and Gaimard, 1832), which spawns multiple times, produces mature oocytes for deposition in a continuous trickle or in larger discrete batches. Throughout a spawning season, developmental stages were assigned to the ovaries of each female by combining macroscopic and histological analyses of the oocytes. Half of the females (46%) showed a significant peak in oocytes at one of the maturation stages, indicating that females were developing eggs in batches. It was hypothesised that the remaining females were also batch spawning, given that the oviduct weights of the remaining females (54%) were high and the other measured biological characteristics were similar to those of the females showing a peak in oocyte stage. Average batch fecundity declined over the 3-month spawning season, but total egg numbers in the ovary increased, suggesting that females might have deposited small batches more often during December. As reproduction requires large allocations of energy, understanding how females distribute reproductive effort throughout their lives is crucial to understanding the behaviour of populations, individuals and their offspring.
Age, growth and cost of reproduction were examined for the small near-shore loliginid squid Loliolus noctiluca in Tasmanian waters, near the southern limit of its distribution. The effects of several factors on hatch size were also evaluated by comparing the statolith natal ring size (NR) from individuals collected in different locations, seasons and years. The life cycle of L. noctiluca was less than six months. July-hatched females grew faster than their May-hatched counterparts, indicating a faster growth in winter-hatched compared with autumn-hatched individuals. There was considerable variation in NRs as function of location, season, year and sex, with females displaying NRs considerably larger than males in any location and year. Immature and maturing females displayed poorer body condition than mature counterparts, suggesting that gonad growth does not affect the mantle or fin growth. A good condition was maintained also in spent individuals indicating that L. noctiluca continued to invest in somatic organs throughout the spawning period. A reproductive strategy closer to ‘multiple spawning’, than to ‘single spawning’ was proposed for this species. Loliolus noctiluca was used as a model to explore the possible effects of climate change on near-shore loliginid populations.
The cost of reproduction for the terminal spawning onychoteuthid squid, Moroteuthis ingens, was analysed using measures of condition and tissue biochemistry. Both males and females showed a dramatic drop in the weight of the gonad in stage 6 (spent) individuals. The mantle weight and nidamental gland weight of females also decreased during the maturation process. Males, however, had a marked increase in both the penis and spermatophoric complex weight in spent individuals, while female oviducal gland weight and nidamental gland length also increased in stage 6 individuals. Residual analysis indicated that testis growth was not developing at the expense of mantle growth, although there was a suggestion of cost to the fins. Females showed that the development of the ovary occurred at a cost to both the mantle and fins. Overall body condition also declined with maturity stage for both males and females, with stage 6 individuals of both sexes in poor condition. Very few females had eggs in the oviducts, suggesting that the oviducts are used as ducts instead of storage organs. Proximal analysis revealed a loss of constituents within the mantle during maturation, with an associated increase in water, indicating the remobilization of energy from the mantle to fuel reproduction. This study suggests that the digestive gland is not used as an energy store in this species.
When using cephalopods as experimental animals, a number of factors, including morality, quality of information derived from
experiments, and public perception, drives the motivation to consider welfare issues. Refinement of methods and techniques
is a major step in ensuring protection of cephalopod welfare in both laboratory and field studies. To this end, existing literature
that provides details of methods used in the collection, handling, maintenance, and culture of a range of cephalopods is a
useful starting point when refining and justifying decisions about animal welfare. This review collates recent literature
in which authors have used cephalopods as experimental animals, revealing the extent of use and diversity of cephalopod species
and techniques. It also highlights several major issues when considering cephalopod welfare; how little is known about disease
in cephalopods and its relationship to senescence and also how to define objective endpoints when animals are stressed or
dying as a result of the experiment.
Temperature is known to have a strong influence on cephalopod growth during the early exponential growth phase. Most captive growth studies have used constant temperature regimes and assumed that populations are composed of identically sized individuals at hatching, overlooking the effects of seasonal temperature variation and individual hatchling size heterogeneity. This study investigated the relative roles of initial hatchling size and simulated natural seasonal temperature regimes on the growth of 64 captive Octopus pallidus over a 4-month period. Initial weights were recorded, and daily food consumption and fortnightly growth monitored. Two temperature treatments were applied replicating local seasonal water temperatures: spring/summer (14–18°C) and summer/autumn (18–14°C). Overall octopuses in the spring/summer treatment grew at a rate of 1.42% bwd−1 (% body weight per day) compared to 1.72% bwd−1 in the summer/autumn treatment. Initial size influenced growth rate in the summer/autumn treatment with smaller octopuses (<0.25g) growing faster at 1.82% bwd−1 compared to larger octopuses at 1.68% bwd−1. This was opposite to individuals in the spring/summer treatment where smaller octopuses grew slower at 1.29% bwd−1 compared to larger octopuses at 1.60% bwd−1. Initial size influenced subsequent growth, however, this was dependent on feeding rate and appears to be secondary to the effects of temperature.
Squid typically display considerable intra-specific plasticity in size and age-at-maturity in response to ambient environmental conditions, yet little is known of the mechanisms driving these variations. We examined the intra-specific variability in Nototodarus gouldi reproductive traits to determine patterns of energy allocation between somatic and reproductive processes over short temporal scales. Females caught during the cool months of May and July were larger, had slower lifetime growth, lower gonad investment, and better somatic condition than females caught during the warmer months, suggesting a trade-off between gonad investment and somatic condition in females. On the other hand, males showed a tight coupling between somatic condition and gonad investment for most months, with increases in somatic and gonad tissue occurring concurrently. In male squid, an increase in lifetime growth rate was coupled with an increase in the relative weights of somatic and reproductive structures, whereas in females, percent increase in body weight per day was correlated only with gonad development. Patterns of repro-somatic investment in mature females had implications for spawning strategies, since female squid with higher levels of gonad investment apparently released batches of eggs together as a group, regardless of body size, whereas females with low gonad investment possibly spawned their eggs independently of one another. In terms of life-history theory, male squid were able to respond rapidly to environmental fluctuations without compromising either the gonad or the soma. However, although mature females did not appear to respond as quickly to ambient conditions, female squid possibly produced two different reproductive strategies, possibly to maximise offspring survival in either a stable or a variable environment. It seems from our study that monthly variations in ambient conditions may have large effects on life-history strategies.
Samples of female Illex argentinus were taken from the catch of a Japanese squid jigging vessel on the Patagonian Shelf during March 1986. Morphometries of the somatic and reproductive organ systems and the histological structure of the mantle in relation to maturation were examined. The data suggest that growth and maturation occur simulta neously during most of the time that Illex argentinus females are on the feeding grounds. In a squid of a 'standard' mantle length the whole body mass increases relative to mantle length during maturation and growth of the reproductive organs. This is accompanied by a small but significant decrease in the relative mass of the mantle, head and viscera whilst the mass of the digestive gland remains constant. Although mantle mass of a 'standard' female squid decreases relative to mantle length with maturity this is not associated with degeneration of the mantle muscles. Energy and nutrient resources for maturation are apparently derived from the squid's food, not from reserves, and during the course of maturation there is an increasing shift of emphasis from somatic growth to production of gonad and accessory reproductive organs.
Size and rates of growth in a cohort of 1+ Arctic charr housed in standard conditions were tracked over 12 months (December to December) and mature and immature males and females compared retrospectively. In both sexes, maturing fish were larger than non-maturing ones. In males, this size differential was the result of differences in growth in winter and early spring, but not in the remainder of the study period. In females, size differentials resulted mainly from growth rate differences immediately prior to breeding. In females but not in males, gonadosomatic index was predicted by growth rates in the months leading up to maturation, and among the females that matured, faster growing fish produced more eggs. Lipid reserves in July were correlated negatively with growth during the previous 7 months and, in females only, lipid reserves were significantly lower in maturing fish then in non-maturing fish, indicating that mobilization of lipid energy reserves in maturing fish had commenced by this time. Variation in investment in gonadal tissue, measured as gonadosomatic index, was not explained by variation in July lipid reserves for either males or females. However, July lipid reserves were negatively correlated with egg number, so females investing more in ova exhibited greater depletion of lipid reserves. These results are discussed in the context of the relationship between body condition and the onset of maturation in salmonids, relative investment in reproduction and sexual differences in the cost of reproduction.
This study presents the results of an analysis of data on length, weight maturity stage, and fecundity of the squid Loligo vulgaris. The data are based on monthly sampling, between January 1991 and June 1992, from the landings of a traditional inshore fishery for squid in southern Portugal. Male squid generally have a lower weight than females of equivalent mantle length. The overall ratio of male to female squid is 1.1, with limited periods during autumn and spring when females outnumber males. Mature males occur within the broad size range 115–605 mm, whilst mature females have a more restricted size range within 175–345 mm. Immature stages I–II dominate the population during June and July, and there is progressive maturation of both sexes stage II to mature squid at stage V, between August and the following March and May in the larger males and females, respectively. There is a significant difference between the sizes at which the different sexes achieve maturity (ML50%), with the male at 245 mm and the female at 227 mm. There is evidence that there are two size modes at which males achieve sexual maturity. It is suggested that maturation of this species takes approximately 8 months in the Algarve. A range of reproductive indices derived from gonad morphometrics in mature squid show a pattern of seasonal development with overall values for gonad maturation indices which are lower during the summer and higher during the autumn to the spring. Fecundity has been estimated by counting the total number of oocytes and ova in the ovary and oviduct of mature (stages IV–V) females. The number of eggs varied between 1441 and 14886 and fecundity was correlated positively with mantle length, body weight, and with length and weight of the nidamental gland.
Cephalopods, like all other animals, have to decide how to allocate resources; maintenance processes, growth of somatic and reproductive tissues, and locomotor activity all have costs. We should like to be able to identify these costs and discover how efficiently cephalopods make use of the prey that they capture and digest. Cephalopods generally grow fast and mature rapidly; a first task is to determine how accurately laboratory studies reflect growth in the wild, because much of the information we need (such as food conversion efficiencies, excretion rates or the costs of locomotion) can be collected only from animals kept in the laboratory. Comparison of laboratory feeding and growth rates for octopods, sepioids and teuthoids with fisheries data suggests that data collected from cephalopods fed ad libitum in the laboratory may be used validly to construct energy budgets representative of individuals in the wild. The immediate cost of feeding (the specific dynamic action) has been thoroughly documented in Octopus, as has the longer-term elevation or depression of metabolic rate by feeding or starvation; it is assumed that similar costs will be found in squid. The cost of locomotion has been studied in both octopods and squid, but we have only limited data on how much time the animals spend moving, and how rapidly, in the wild. Excretory and faecal losses are assessed from laboratory studies, and maintenance costs estimated from feeding rates that just maintain body mass in the laboratory. Comparison of gross and net food conversion efficiencies suggest that squid convert food into tissues less efficiently than octopods, owing primarily to their greater time spent in locomotion. We present a representative series of energy budgets for octopods (based on Octopus) and squids (based on Illex and Loligo), for starving, feeding, migrating and maturing individuals. A major contrast is provided by Nautilus, which lives for ten or twenty years and grows only slowly. Finally we speculate on the possible biochemical and historical factors that may have limited the adaptive radiation of cephalopods, resulting in a group lacking herbivores, detritivores or filter-feeders but extremely successful as carnivores.
In yellowtail rockfish (Sebastes fiavidus), lipids that accumulated in mesenteries and liver during the summer and early fall upwelling were subsequently translocated to developing ovaries during late fall and winter. Tissue and serum lipids were assessed by stage of ovary maturation from fish collected monthly over six annual reproductive cycles (1985–91) from Cordell Bank, a seamount off central California. Lipids were primarily transported to ovaries prior to fertilization. Energetic lipids (triglycerides, nonesterified fatty acids) were maximal in serum during yolk accumulation stages and declined significantly during embryonic stages. Between fertilization and parturition, lipid and protein content of ovaries declined by about 21%, a value approaching the minimum for lecithotrophy (i.e. ovoviviparity). During gestation, however, serum phospholipids and calcium (vitellogenin surrogate) were significantly elevated relative to male levels, suggesting matrotrophic contributions. A reproductive mode that is primarily lecithotrophic but supplemented by maternal inputs during embryogenesis would be beneficial to viviparous fishes of the California coast. This strategy may optimize reproduction by coupling the disparate times of food abundance and gestation, yet allow for provision of nutrients late in the reproductive cycle should they be available.
We studied the condition of stoplight parrot-fish, Sparisoma viride, collected from the fringing reef of Bonaire (Netherlands Antilles) between March 1987 and October 1991. To this end, we compared length-weight relationships using analysis of covariance. The condition of different life phases [juveniles, initial phase (IP) and terminal phase (TP) adults] and social categories (territorial and group adults) is compared in different seasons, taking into account spatial variability along a depth gradient. Variations in condition are related to differences in behaviour, the use of space and the distribution of food. The average length weight relationship of fish with empty guts is described by the equation: WEmpty = 9.115 x 10 -6 X FL 3"1r176 (n = 386, R 2 = 99.82%, W in g, FL in ram). Territorial TP males were found to be in poorest condition, whereas (sexual-ly inactive) group TP showed the best and IP fish an intermediate condition. These differences are ascribed to varying investments in territory defence and repro-duction, which affect condition more than the vertical distribution of food. All categories were in minimum condition between May and July, the season with longest day lengths and increasing water temperatures. This seasonal effect cannot be ascribed to increased reproductive effort and suggests that the higher ener-getic demands due to the longer active period of fish are not completely met by increased food uptake. It is inferred that food may be a limiting factor at times.
Samples of Loligo
gahi from the Falkland Islands Interim Conservation and Management Zone collected in March 1987 were analysed to determine the relationships between mass of reproductive and somatic organs during maturation. There was a progressive increase in mass of the reproductive organs with growth in males, while in females these organs did not show a conspicuous increase in mass until a body mass of c. 40 g was reached. No change was found in the mass of the digestive gland in relation to body mass or in the water content of male and female somatic tissues during maturation. Growth of reproductive organs in L.
gahi seems to be supported by diet and not at the expense of somatic tissue.
The digestive gland of the tropical sepioid Idiosepius pygmaeus (Steenstrup) (Cephalopoda: Idiosepiidae) is characterized by a single cell type which secretes proteinaceous spherical bodies, the secretory spheres. Changes in the structure of the gland with feeding were investigated through a field sampling programme and a laboratory feeding experiment. Specimens were collected in the field on three consecutive days. There was a significant increase in the number of spheres during the day. A laboratory-based night trial showed that numbers of secretory spheres remained high during the night. After feeding there was a rapid and marked increase in the number of secretory spheres, suggesting that upon registering a stimulus the digestive gland secretes large amounts of enzymes. The process is rapid with an increase in the number of spheres occurred one hour after feeding. A second peak occurred 16 hours after feeding, suggesting that there may be two phases to the digestive cycle. This study examined natural and experimental patterns in the digestive gland and estimated the time involved in the digestive activity of I. pygmaeus.
The mantle muscle tissue of cuttlefish is predominantly made up of circular muscle fibres which run around the body. This circular muscle tissue is divided into discrete blocks by radial fibres, which run perpendicular to the main axis of the body. Growth of mantle muscle tissue was described in the tropical cuttlefish Sepia
elliptica by examining muscle block size and the density and size distribution of muscle fibres. Changes in these variables were assessed in juvenile and adult cuttlefish. Generation of new muscle fibres, both within new and existing muscle blocks, occurred as animals grew across the size range. Anterior muscle blocks were smaller than muscle blocks in the middle and posterior regions of the mantle, suggesting that new blocks were generated anteriorly. Muscle blocks were also created in the middle and posterior regions by division of existing large blocks into small blocks by generation of circular and radial muscle fibres. The examination of cuttlefish muscle growth dynamics provided an alternative way of assessing cephalopod growth mechanisms.
Samples of male Illex argentinus were taken from the catch of a Japanese squid jigging vessel on the Patagonian Shelf during March 1986 and an analysis was carried out on the morphometrics of the somatic and reproductive organ systems in relation to maturation. The data show that growth and maturation occurred simultaneously during most of the time that Illex argentinus males were on the feeding grounds over the southern Patagonian Shelf. In a squid of a ‘standard’ mantle length the whole body mass increased relative to mantle length during maturation and this could be attributed to the increase in mass of the reproductive and accessory reproductive organs. During maturation the mantle and digestive gland mass showed no significant change relative to mantle length. The mass of the head increased and the mass of the viscera decreased relative to mantle length. In male Illex argentinus, as in the female, the energy and nutrient resources for maturation are derived from the squid's food and during the course of maturation there is an increasing shift of emphasis from somatic growth to production of gonad and accessory reproductive organs. The proportional investment of body mass in reproductive and accessory reproductive organs predicted for a fully mature male Illex argentinus was less than half that of the female.
Size and rates of growth in a cohort of 1 + Arctic charr housed in standard conditions were tracked over 12 months (December to December) and mature and immature males and females compared retrospectively. In both sexes, maturing fish were larger than non-maturing ones. In males, this size differential was the result of differences in growth in winter and early spring, but not in the remainder of the study period. In females, size differentials resulted mainly from growth rate differences immediately prior to breeding. In females but not in males, gonadosomatic index was predicted by growth rates in the months leading up to maturation, and among the females that matured, faster growing fish produced more eggs. Lipid reserves in July were correlated negatively with growth during the previous 7 months and, in females only, lipid reserves were significantly lower in maturing fish than in non-maturing fish, indicating that mobilization of lipid energy reserves in maturing fish had commenced by this time. Variation in investment in gonadal tissue, measured as gonadosomatic index, was not explained by variation in July lipid reserves for either males or females. However, July lipid reserves were negatively correlated with egg number, so females investing more in ova exhibited greater depletion of lipid reserves. These results are discussed in the context of the relationship between body condition and the onset of maturation in salmonids, relative investment in reproduction and sexual differences in the cost of reproduction.
This study assesses the potential of the tropical loliginid squid Photololigo sp. to lay multiple batches of eggs and examines changes in somatic growth during reproduction. Histological analysis of the ovary and the relative size of the oviduct to mantle weight and ovary weight were used to determine the potential for multiple spawning. Ovaries of mature females always had immature and mature oocytes present, suggesting that not all the oocytes were maturing simultaneously and that multiple batches of eggs were being produced. Furthermore, poor correlations of oviduct weight with body size and ovary weight indicated that mature oocytes were not accumulating in the oviduct for a single spawning event. Both these observations supported the hypothesis that Photololigo sp. has the potential to lay multiple batches of eggs throughout its life. Specific growth rates, length-weight relationships, relative growth of somatic and reproductive tissue and microscopic assessment of muscle tissue were compared between immature and mature females. Growth rates of immature females were almost twice as fast as those of mature females. Mature females also had no large muscle fibres present, suggesting that energy for reproduction was mobilised from the muscle tissue.
The population biology of Loligo vulgaris and Loligo forbesi in Galician waters is described based on monthly samples from the fishery obtained during the period February 1991–June 1992. Maturity was assessed using a maturity scale and indices. The estimated number of oocytes in mature females varied from 782 to 21 885 in L. vulgaris and from 1317 to 14 956 in L. forbesi, and showed a slight positive correlation with the length of the mantle (ML) for both species. Oocytes in the ovaries fall into three discrete size classes, which suggests that L. vulgaris and L. forbesi are intermittent or multiple spawning species. In L. vulgaris males mature at two different modal sizes, hence perhaps at two different ages, while in L. forbesi this occurs in both males and females. Males mature earlier in the season than females in both species. The maximum number of spermatophores found was 1010 and 1000 in two L. vulgaris males with 119 mm and 400 mm ML respectively, and 1035 in a L. forbesi male with 150 mm ML. In both species, spermatophore length increases with ML. Loligo forbesi males maturing at a larger size produce fewer but larger spermatophores than those maturing at a small size. Loligo vulgaris spawn throughout the year, but the period of more intensive spawning extends from December to April. The breeding season of L. forbesi extends from December to May, the more intensive spawning extending from December to February. Sex ratios were variable for both species. Age and growth for both species and sexes were estimated by examining growth increments in the statoliths. Like-sized individuals had different ages in both species. The life span of L. vulgaris was estimated at about 1 year while L. forbesi seems to reach an age of 15–16 months. A list of prey species found in gastric contents of both species is given. The diet of L. vulgaris comprises fish (86.8%), cephalopods (6.0%), crustaceans (3.0%) and polychaetes (1.8%), and the diet of L. forbesi includes fish (75.6%), crustaceans (18.5%) and cephalopods (4.4%).
The reproductive pattern of Loligo vulgaris and Loligo forbesi was studied on the basis of gonad maturation, mating and spawning in males and females of both species which were present off the northwest coast of Spain (Galicia), between February 1991 and February 1993. The mature females of both species have several modes of egg sizes and developmental stages within the ovary. Several signs indicate that both female Loligo vulgaris and L. forbesi undergo partial ovulation at the time of spawning, the spawning period being relatively long, although in no case representing the greatest fraction of the animal's life before death. Egg-laying occurring in separate batches and somatic growth between egg batchs has not been observed. This reproductive pattern is defined as intermittent terminal spawning. Some other terms describing different cephalopod reproductive strategies are also defined.
The role of the digestive gland, with respect to non-structural lipid, was examined using proximal analysis, histochemistry and quantitative histological techniques in the tropical loliginid squids Sepioteuthis lessoniana (Lesson) and Photololigo sp. The digestive gland of both species was characterized by large and numerous lipid droplets in the apical portion of the digestive cells and very few in the basal portion. The apical lipid droplets were released into the lumen of the gland and subsequently rapidly removed. Despite the numerous large apical lipid droplets, the lipid concentration in the digestive glands of S. lessoniana and Photololigo sp. was lower than that reported for most squid species. There was no relationship between lipid concentration and stage of digestion, suggesting that lipid is not stored in the gland after a meal. There was also no relationship between lipid concentration and the sex of an individual or stage of reproductive maturity, suggesting that these squids are not storing lipid in the digestive gland for use in fuelling reproductive maturation or providing an energy source for oocytes. I believe this study is the first to combine proximal analysis and quantitative histological techniques to examine the role of the squid digestive gland with respect to non-structural lipids. The results indicate that the digestive gland of these tropical loliginid squids is excreting, not storing, excess dietary lipid.
Individuals of the tropical loliginid squid Photololigo sp. 1 were collected from the tropical waters of the northwest continental shelf of Australia. Both males and females exhibited pronounced phenotypic variation in size at maturity. Statolith increment analysis was carried out to determine individual age. On the basis of the assumption that statolith increments were deposited daily, counts revealed that this species had a short life-span and that all individuals were younger than 160 d and exhibited linear growth over the size range sampled. All of the longest squid collected were females, which achieved this size disparity predominantly by being older than males rather than by growing at a faster rate. Age analysis revealed that small mature individuals were considerably younger than large mature individuals. A large size distribution of mature individuals was therefore achieved by variation in age at maturity. Possible causal mechanisms are considered.
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
The proximate (protein, lipid, carbohydrate and ash) and elemental (C, H, N and P) composition of the major tissues were measured for 18 male and 51 female Illex argentinus sampled from the feeding grounds over the Patagonian Shelf. In most tissues the chemical composition did not vary with sexual maturity, although the mass of the tissue increased significantly because sexual maturation and growth were proceeding simultaneously. The composition of the ovary and associated tissues (nidamental gland, oviducal gland) did change significantly during sexual maturation. Several tissues contained significant amounts of one or more unknown components. The nitrogen content of an unknown component in the testis was similar to that of DNA. In the spermatophoric complex the nitrogen content suggested the unknown fraction may be an amino acid or short peptide, whereas in the nidamental gland the nitrogen content suggested an amino-sugar or polysaccharide derivative. The digestive gland was rich in lipid and continued to accumulate substantial reserves of energy throughout the period of sexual maturation on the feeding grounds. During this period there was no evidence for the utilization of either digestive gland or mantle tissues to supply energy for gonads. Accumulation of carbon and energy (estimated stoichiometrically from carbon) during the final 50 days on the feeding grounds indicated that energy demands for tissue synthesis in females were almost twice those of the smaller males, and that a relatively small fraction of the demands were for reproductive tissues (5% in males, 15% in females). Most energy intake in this period was directed to the digestive gland (40% in males, 47% in females) and other somatic growth (54% in males, 38% in females). A preliminary power budget suggested that during the final days of feeding before migrating to the spawning grounds, energy intake of Illex argentinus is 4-5% body energy content per day, growth efficiencies are low (17-22%) and that energy reserves in the digestive gland would fuel migration in the absence of feeding for 14 days in males and 21 days in females.
Body condition indices were assessed for pelagic juvenile cod [14 to 31 mm standard length, SL] over 2 cruises in spring 1987 in Canadian Atlantic waters on the southern Scotian Shelf. Three different indices determined from the residuals of univariate regressions were [1] triacylglycerol [TAG] content on standard length [SL], [2] dry body weight on SL, and [3] back-calculated change in SL from the peripheral 14 daily growth increments of the otolith on SL; hereafter referred to as TAGSL, DWTSL, and OTOSL respectively. Correlations between indices declined from TAGSL:DWTSL [0.69, 0.64, cruises 87-1 and 87-2 respectively], to TAGSL:OTOSL [0.38, -0.05], to DWTSL:OTOSL [0.05, 0.03], a surprisingly low correlation considering that the indices were derived from the same individual. This pattern was also demonstrated by a principal component analysis (PCA), showing that after the first [size] component, otolith-based growth alone loaded on PC 2, then TAG contrasted with SL loaded on PC 3, and dry body weight showed the highest correlation with the starvation-independent SL. Supplementary analyses from 4 other cruises during 1985 and 1986 confirmed the weak correlation between DWTSL, OTOSL and other morphometric measures. All indices were positively correlated with zooplankton biomass, but of the 16 separate cruise by index comparisons, only 6 were significantly correlated with zooplankton, of which 3 were the OTOSL. The rapid somatic/otolith growth of pelagic juvenile cod may respond rapidly to prey abundance, and rapid growth may preclude accumulation of lipids [TAG], indicating that the utility of a condition index will depend on the species and life stage examined. Indices of recent otolith growth appear good measures of pelagic juvenile cod condition.
A number of reproductive indices were compared with a subjective maturity scale for assessment of Loligo forbesi maturity. The ratio between nidamental gland length and mantle length corresponded well with female maturation, as did the
ovary mass-soma mass and nidamental gland mass-soma mass ratios. For males, the ratio between spermatophoric complex mass
and somatic mass was found to be the most suitable for maturity assessment. The timing of recruitment and maturation of L. forbesi in Irish waters was described from the size and maturity of squid in commercial landings in the south of Ireland during the
years 1991–1993. Immature squid first appeared in commercial catches in July and August, and this represented the main period
of recruitment. A second period of recruitment was apparent in December 1991, but was not identified in the 1992–1993 season.
Mature females were present in the commercially exploited population between November and April, with a small number also
found in the summer. The abundance of egg masses was used to indicate timing of spawning. Egg masses recovered from the Cork
coast indicated that peak spawning occurred during the winter months, but continued on a small scale for much of the year.
The convergent evolution of cephalopods and fish has often been discussed on an anatomical basis, but recent advances in the knowledge of cephalopod life cycles, physiology, and biochemistry suggest that there are constraints on cephalopods that prevent them from competing directly with fish. These advances are reviewed against the background of detailed information on fish from the perspective that the basic inefficiency of the jet-propulsion system has required bioenergetic, physiological, and biochemical adaptations in squid which maximize their metabolic rates. Such "high-energy" adaptations are suggested to have resulted in the short life history and semelparous reproductive patterns that seem to characterize these coleoid cephalopods. Conversely, the physiology and biochemistry offish give them distinct advantages for long lives and iteroparity.
An energetics mechanism is proposed to explain the trade-off between current and future reproduction. Surplus energy can be used for reproductive tissue (current reproduction) or somatic tissue (needed for future reproduction); therefore, we needed to determine first, when does growth of somatic and reproductive tissues occur, and second, how and when is energy allocated to reproduction. Walleye were sampled monthly from the commercial fishery in Lake Erie. Morphological attributes were recorded from these walleye, as well as the lipid composition of a smaller subsample. Energy for reproduction is acquired in the winter, spring, and summer before spawning and stored as visceral lipids. Ovarian lipids are largely derived from visceral fat deposits; thus, females appear to be capital breeders. Females elaborate gonadal tissue only if there is sufficient visceral fat. The circannual endocrine switch to reproduction may occur in midsummer (August) and in October. Females may discontinue ovarian development during the early winter if there is insufficient surplus energy (visceral fat). Year-class variation may be partly explained by the energy condition of the females and the proportion of the stock able to spawn successfully each year.
Validated size-at-age data are presented for two tropical squid species (Loliolus noctiluca and Loligo chinensis) and a sepioid (Idiosepius pygmaeus). Estimates of age were obtained from daily increments in the statolith. All species reached adult size in less than 200 d. For each species, growth in mantle length was linear over the sizes sampled. In L. chinensis, growth was fastest during December–January (summer), with males showing faster growth rates than females. For I. pygmaeus, females generally had a higher growth rate than males. The slowest growth rates for both sexes occurred in the August–September (winter) period. The size-at-age data indicated rapid linear or exponential growth and a short life span of less than 1 yr. In contrast, growth curves generated from analysis of length frequency data (ELEFAN software package) suggested an asymptotic growth curve and ages in excess of 3 yr, and such analyses therefore appear inappropriate. The results of this study and a review of the literature revealed that rapid growth and short life span is the norm for pelagic cephalopods, with tropical species growing considerably faster than their temperate counterparts.
A link is proposed between the processes that led to the evolution of large species of squid and the highly variable, cyclic recruitment seen in squid fisheries. Maximum growth requires maximal feeding and minimal routine metabolism at optimum temperatures, which decrease as squid grow. Topographically induced upwelling zones, inshore of western boundary currents, provide productive environments with appropriate temperatures for all life stages. Most squid are small and live in the tropics or subtropics; locomotor constraints prevent them from swimming long distances. Long annual migrations to spawn upstream in current systems require short-lived squids to maximize rates of growth. Therefore, such systems provide the opportunity and a powerful selective advantage for large size and rapid growth. Increased fecundity and cannibalism provide additional directional selection for large individuals. Current systems show food production peaks (blooms); paralarval release must match these to increase survival. Because squid are semelparous, disruption of delicately balanced lifecycles by physical events can virtually annihilate stocks. Recovery probably requires that populations of large squid "re-evolve" from smaller, more-stable tropical populations of small squid. This recovery phase may extend the "down-side" of abundance cycles. Studies of squid/current systems have focused on western boundary currents, but the Illex complex also associates with eastern boundaries. Such populations are generally smaller than in larger systems, supporting the hypothesis, but more detailed comparisons are required.
Age and growth were estimated in the European squid, Loligo vulgaris, by examining growth increments in the statoliths of 203 specimens collected from off the French Mediterranean coast. Length and increment data were analyzed assuming that the increments were formed daily. The relationships between age and length showed that: growth rate varied considerably among individuals; growth was double exponential; the squids grew on average to 240 mm ML at 240 d from hatching, with a maximum of 350 mm at 240 d; the life span is probably about one year.
Maturation in the onychoteuthid squid Moroteuthis ingens was found to be irreversible, with death following shortly after sexual maturation and spawning. Both males and females were found with spent gonads. The ovary reaches very large sizes in mature females and probably prevents feeding by constricting the caecum. There was also a marked difference in the tissue integrity between immature females and females which had reached sexual maturity. Mature and spent females showed advanced tissue breakdown with individuals having a thin mantle wall with an inelastic, gelatinous appearance. Histological examination of the mantle wall revealed that the tissue breakdown was due to a drastic histolysis of muscle tissue and, to a lesser extent, collagen fibres. Mature males also showed some tissue breakdown and loss of muscle fibres but this was not as dramatic as in the females. These features are considered in relation to processes contributing to terminal maturation in M. ingens.
Mantle muscle tissue of Idiosepius pygmaeus was examined to describe changes in structure and organization associated with growth. Growth in I. pygmaeus|DD was a function of both an increase in muscle fibre number and fibre size within muscle blocks. Continuous fibre production over the observed life span of I. pygmaeus was indicated by the presence of very small muscle fibres (< 1.0 μm in diameter) in substantial proportions in all sizes of individuals. Muscle blocks became larger as animals increased in size, although new muscle blocks were generated in all sizes of individuals. Mantle muscle fibres had a maximum size of 11 μm. Therefore, for an individual to continue increasing muscle block sizes, new fibres must be produced. This is further evidence of continuous fibre production throughout the size range of I. pygmaeus examined. The relative rates of muscle fibre generation and fibre growth depended on the size of the animal and position along the mantle (anterior, mid or posterior mantle). The predominance of small fibres and blocks at the anterior end of the mantle suggested that this was the primary growth region. Mitochondriapoor and mitochondria-rich muscle fibres from small individuals had much larger mitochondrial cores than muscle fibres from larger animals. Changes in the muscle structure are discussed with respect to the metabolic and energetic requirements of I. pygmaeus, and how these may change with growth.
Four species ofPhotololigo were identified using allozymes from the northern waters of Australia between the North West Shelf (11400E) and Brisbane (15300E). Two of these species fitted the gross morphology ofP. edulis documented from Japan and two taxa shared the distinguishing features ofP. chinensis. F-statistic analyses revealed no major population genetic structuring in any of the species over the geographical range sampled and all populations were in Hardy-Weinberg equilibrium. Given that the distributions of the species appear to be correlated with depth, at least during the austral summer, this panmixia is considered to reflect extensive gene flow through longshore movement of these squid. It is suggested that depth constraints, or factors associated with depth, act as effective barriers to gene flow and, therefore, provide mechanisms for allopatric speciation in this genus. The data from northern Australia indicate that the current view thatLoligo species have broad distributions may need revision and that a number of widespread taxa (such asP. edulis andP. chinensis) are likely to comprise a series of hitherto unrecognised allopatric sibling species. Heterozygosity levels were low for all species exceptPhotololigo sp. 1, which had a restricted deep-water distribution. These data are concordant with the habitat specialist-generalist model, which is discussed.
Body size at sexual maturity, egg-size distributions, and potential reproductive output have been estimated for female and male squid, Loligo forbesi Steenstrup, off the west coast of Scotland. Two size modes at maturity were found in both sexes, but separation into size cohorts was more pronounced in males (180 and 350 mm mantle length, ML). Preliminary ageing studies based on statolith ring-counts suggest that these size modes are not due to different age groups at breeding. Females have a single size mode of mature eggs in the proximal oviduct, but may have at least two size modes of eggs within the ovary. This finding is interpreted as evidence of batch-spawning in this squid. There was a weak relationship between total egg numbers (range 1000 to 16000) and body size (range 196 to 318 mm ML) and between mature egg size and body size. Males showed a strong positive relationship between spermatophore length and body length but a weak relationship between total number of spermatophores and body size. The results are discussed in the context of flexibility of breeding strategies in the loliginids and variety of life-cycle patterns.
The oogenic cycle and biochemical composition of the ovary of raft-cultured great scallop (Pecten maximus) were studied during the period April 1990–July 1991. The ovary condition index (FGI) and stereological studies showed the existence of two principal spawning periods, winter and late spring-early summer. No sexual resting period was found. Oocyte lysis was high throughout the year. Ovarian lipid levels displayed a clear seasonal pattern linked to the gametogenic cycle. Total lipid (TL, 16–21% dry weight), acylglycerol (AG, 20–65% TL) and free sterol (FS, 2.8–6.4% TL) levels were, generally, higher in the ripe ovary and a decrease coincided with spawning. Protein (59–63% dry weight), glycogen (r
s = 0.779, p < 0.001),="" and="" ag="" (%="" f="" tl)="" correlated="" well="" with="" the="" mean="" oocyte="" diameter="">r
s = 0.630, p < 0.01)="" and="" the="" female="" gonad="" condition="" index="">r
s = 0.443, p
Growth, reproduction and gross biochemical composition of the Manila clam Ruditapes philippinarum were studied for one oceanic and two inner stations in the Bay of Arcachon, France, from March 1989 to March 1991. During this period, sea-water temperature, salinity and chlorophyll a were also recorded. A marked increase in length occurred during the first year in all areas, after which growth rates decreased. In contrast, weight increased more steadily. The Manila clam exhibited best development in the oceanic area, but there was no difference in growth of clams between the two inner stations. Differences in growth between oceanic and inner stations may result from differences in fluctuations of environmental conditions such as temperature and salinity. Except for higher carbohydrate contents in clams recovered in autumn from the oceanic station Le Ferret, biochemical components differed little between stations. During the second winter, glycogen levels were relatively low, but no mortalities were recorded. On the other hand, sowing spat in autumn instead of spring or sowing larger-sized spat did not reduce the time required for culture of R. philippinarum.
Changes in the biochemical composition of the digestive gland and in the proteins of the mantle muscle of Sepia officinalis L, collected in September 1989 from the Ria de Vigo (northwest Spain), were measured during periods of 2, 4, 10 and >53 d starvation. The digestive gland lost weight faster than the rest of the body throughout the whole period of starvation. In the digestive gland, carbohydrate and protein contents did not change during starvation; however, lipid levels decreased significantly after 53 d. Phospholipid content increased during longterm starvation. The content of free fatty acids rose after 16 d. Sterols, diacylglycerylethers, triacylglycerols and carotenoids contents did not change significantly. Of the total fatty acids, 18:0, 20:2n6, 20:4n6 and the monounsaturated moieties were preferentially consumed; others, such as 22:5n3, 22:6n3 and 16:4n1, were selectively retained. In the mantle muscle, water content increased and total protein content decreased. The myofibrillar proteins decreased after 53 d starvation, whereas the sarcoplasmic fraction did not change and the stromatic proteins increased. No changes were observed in the electrophoretic patterns of sarcoplasmic and myofibrillar proteins. The digestive gland of S. officinalis does not seem to be an important reserve organ during long-term starvation, but does seem to be important during shortterm starvation.
In an attempt to describe the biochemical events associated with the main stages of the annual and reproductive cycles of
the female dog cockle Glycymeris glycymeris L., we studied seasonal variations in the various stages of oocyte development of the ovaries, and the glycogen, total protein
and total lipid content of five body tissues – adductor muscle, foot, tunic coat, visceral mass and mantle. From November
1991 to November 1994, microscopic examination of the ovaries and measurement of the tissue concentrations of glycogen, total
proteins and total lipids in these five body tissues were made monthly on ten female dog cockles originating from the sea
area around Douarnenez (south Brittany, France). Morphological studies revealed that in the population investigated the annual
cycle is characterised by three major periods: a first period of vitellogenesis extending from February/March to April/May
and preceding a spawning in spring; a second period of vitellogenesis extending from May/June to September/October and leading
to either no spawning, a single autumnal spawning event, or to two spawning events in summer and autumn; and a third period
extending from October/November to February/March and characterised by a high level of oocyte lysis. In the muscular body
tissues of the dog cockle, i.e. the adductor muscles, the foot and the tunic coat (the muscular envelope containing the visceral
mass), the concentrations of glycogen, total proteins and total lipids underwent very similar variations during the annual
cycle. During each stage of vitellogenesis, a typical glycogen–protein–lipid sequence was observed in the muscular tissues
that was characterised firstly by a peak of glycogen concentration 2 to 3 mo before spawning, followed by a peak in total
proteins 1 mo before spawning, and finally by a peak in lipid content just before spawning. A similar glycogen–protein–lipid
sequence was also recorded in the first half of the winter period. However, these events were followed by general atresia
affecting all oocytes in the gonad. Maximum energetic value of biochemical constituents in females coincided with peaks in
lipid content in the visceral mass and mantle. These biochemical events occurred principally immediately before and at the
end of oocyte lysis (December/January). A drop in the total energetic value, affecting mainly the visceral mass and the mantle,
was recorded each year during the period January to March, coinciding with the period of shell growth in this species. Our
data clearly indicate that in female G. glycymeris all muscular tissues contribute to the storage of glycogen and proteins, and suggest that glycogen may be the source of energy
triggering vitellogenesis. Biochemical and microscopic observations revealed that oocyte development takes place during the
first half of winter, but that these oocytes undergo atresia in December/January. The metabolites produced from oocyte lysis
could contribute to somatic growth, which occurs in late winter.
The biochemical composition of larvae of Teredo navalis L. and Bankia gouldi (Bartsch) (Bivalvia: Teredinidae) was examined throughout larval development at 23°C and 30–32%. salinity in the presence of the phytoplankton food Isochrysis aff. galbana (clone T-ISO), during a delay of metamorphosis in the presence of food but absence of a wood substratum and during periods of enforced starvation. Newly released Teredo navalis larvae had a mean length (L) and height (H) of 89.3 and 76.1 μm respectively. The first appearance of pediveliger larvae at 212.1 μm L and 230.0 μm H occurred 27 days after release. Larval dry weight increased from 0.29 μg to 1.96 μg during this period. Newly formed straight hinge larvae of Bankiagouldi had dimensions of 62.8 μm L and 49.8 μm H. Metamorphically competent B. gouldi larvae had dimensions of 230.0 μm L and 282.9 μm H and were first observed 20 days after fertilization. Larval dry weight increased from 0.06 μg to 2.20 μg during this period. During enforced delay of metamorphosis the ash-free dry weight of Teredo navalis larvae decreased whereas the ash free dry weight of Bankia gouldi larvae increased. During the early period of shelled larval development both species showed similar decreases in lipid, protein and carbohydrate levels (μg·mg dry weight−1); however, this was reflected in a decrease in biochemical content (μg·larva−1) only in Teredo navalis. During enforced starvation the major proportion of both the weight and caloric losses were due to protein. Lipid also contributes significantly to these losses whereas the contribution of carbohydrate was small. Larval oxygen consumption rates were determined directly by manometry and indirectly by estimates of decrease in caloric content during periods of enforced starvation. Direct and indirect determinations for T. navalis are described by the relationships R = 1.16 W1.05 and R = 0.98 W1.24 respectively where R is the respiration rate in nl O2 · larva−1 · h−1 and W is dry weight inclusive of shell in μg. Direct and indirect determinations for Bankia gouldi are described by the relationships R = 1.37 W1.25 and R = 1.81 W1.25 respectively. When data for both assay procedures are combined for each species the relationships R = 1.10 W1.07 and R = 1.44 W1.18 are obtained for Teredonavalis and Bankia gouldi respectively.
Biological and fishery features of the waves of abundance of Illex argentinus in three fishery regions −52°S (shelf with 180–230 m depths in exclusive economic zone of Argentina—EEZA), 46° and 42°S (continental slope with 600–800 m depths off the EEZA) in April–June 1990 were studied. According to age analysis of 629 statoliths made aboard, age-length structure of each wave of abundance were determined. In April–June active spawning migrations of I. argentinus were observed from feeding grounds located in limits 50–52°S along the continental slope northwards through 46° and 42° fishery regions. Only winter-hatched squids (hatched from June to September of the previous year) took part in migrations which were observed as waves of abundance in all three regions. Each migratory wave of abundance consisted of 2–4 successive monthly generations. The start of spawning movement was corresponded with the age and maturity state of the squid. Squid of all monthly generations began migrating from the 52°S region at a mean age of approximately 250 days, passed through 46°S at mean age 280 days and through 42°S at mean age 295 days. Males migrated 2–3 weeks earlier than females of the same generation. Rates of somatic growth were very low during migrations from 52° to 46°S (RDGR - 0.13% mantle length (ML) in mature males and 0.2% ML in maturing females). During movement from 46° to 42°S and, obviously further, mature squids practically ceased somatic growth. Estimated rate of migrations was 23.2–28.9 km day−1 (including current velocity), or 26–30 cm s−1 (0.47 body length s−1). Spawning was considered to occur on the continental slope of Uruguay and Brazil north of 35°S in July–August. Methodical approaches of efficient determination of squid age, growth and stock structure by means of investigation of squid biological features and statolith microstructure in each distinguished wave of abundance were elaborated.
1. Octopus vulgaris can be forced into precocious maturity by removal of the subpedunculate lobe from the brain, an operation that releases the optic glands from inhibition, and allows them to secrete a gonadotropin. 2. 14C-leucine was injected into the bloodstream of immature animals and its subsequent incorporation into muscle protein followed by taking successive samples from the arms. The optic glands were then activated, and a further injection of 3H-leucine given and followed by means of further arm samples. 3. Optic gland secretion suppresses protein synthesis in the muscles. This is associated with an increase in the total amino acid pool in the muscles and with a considerable increase in the concentration of free amino acids circulating in the blood. 4. If an ovary is present these events are associated with a rapid growth of the ovary and its ducts, and a loss of weight elsewhere. In ovariectomized animals the ducts grow, but there is no yolk to absorb the large pool of free amino acids, and the animals gain weight by osmotic uptake of water into the muscles. 5. The developing ovary may produce a hormone that increases the release of amino acids from muscle, since the concentration circulating in the blood of intact animals remains at least as high as in ovariectomized octopuses, despite the demands of the developing ovary. 6. These matters are discussed in relation to other evidence for a gonadial hormone and in relation to the 'self-destruct' effect of the optic gland secretion in determining the post-reproductive death of octopuses.
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
The reproductive strategies of bivalve molluscs
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Squid maturity scales for population analysis
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Description of growth in a tropical cuttle®sh using muscle tissue: asymptotic or non-asymptotic growth?
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growth in a tropical cuttle®sh using muscle tissue: asymptotic
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