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Reproductive biology of the starfish Pharia pyramidatus (Echinodermata: Asteroidea) from the Mexican Tropical Pacific
Abstract
The starfish Pharia pyramidatus is a tropical species of high ecological importance, mainly because of its role as generalist predator. Nevertheless, there are no studies about its reproduction. This study analysed the reproductive biology of P. pyramidatus based on monthly time-series samples from April 2008 to March 2009 at Isla Montosa in the Mexican tropical Pacific. The gonad index (GI), and pyloric caecum index (PCI) were determined and the results were corroborated by histological examination of the gonads. Pharia pyramidatus is a gonochoric asteroid and the ratio of males to females was not significantly different throughout the year. Gametogenesis showed high synchrony among males and females and five stages were recognized for both sexes. Spawning occurred from July to September. Maximum oocyte size was �150 mm and mean fecundity was 7.3+ 1.2 millions of oocytes per female. GI and PCI showed seasonal variations and an inverse relationship from May to August. Sea-bottom temperature and photoperiod showed a direct relationship with GI, and apparently constitute the proximate causes of the seasonal reproductive pattern observed in P. pyramidatus, while the highly seasonal rainfall and strong upwelling probably act as ultimate causes.
... Microscopic examination of the sections allowed sex determination and assignation of each individual to a gonad maturation state. Development was divided into five stages based on an adaptation of scales used for other asteroid species, where each stage is determined according to the frequency and characteristics of gametes, presence of phagocytes and cell remains, as well as thickness and shape of the gonadal wall [4,9,10,32,38]. ...
... Relations among PCI, temperature, photoperiod and Chl a (independent variables) with the reproductive cycle represented by GI (dependent variable) were assessed through a step-by-step multiple linear regression analysis (GLM) using STATA v1.2 statistical Software (Stata Corporation, College Station, TX, USA). Statistical significance was accepted at p < 0.05 [4]. ...
... Results showed that both A. aranciacus sexes had a synchronous gametogenesis but females reached the maturity stage slightly earlier than males, in accordance with previous results obtained in Asterias amurensis by Byrne et al. [9]. The studied A. aranciacus population did not differ significantly in the male-female proportions, coinciding with previous results in other sexually reproducing asteroids (since sex-ratios can be highly biased in the case of asexual asteroids) [4,26]. The development of the A. aranciacus gonads reflected that mature and partially spawned individuals remained for an extended period of time. ...
... Microscopic examination of the sections allowed sex determination and assignation of each individual to a gonad maturation state. Development was divided into five stages based on an adaptation of scales used for other asteroid species, where each stage is determined according to the frequency and characteristics of gametes, presence of phagocytes and cell remains, as well as thickness and shape of the gonadal wall [4,9,10,32,38]. ...
... Relations among PCI, temperature, photoperiod and Chl a (independent variables) with the reproductive cycle represented by GI (dependent variable) were assessed through a step-by-step multiple linear regression analysis (GLM) using STATA v1.2 statistical Software (Stata Corporation, College Station, TX, USA). Statistical significance was accepted at p < 0.05 [4]. ...
... Results showed that both A. aranciacus sexes had a synchronous gametogenesis but females reached the maturity stage slightly earlier than males, in accordance with previous results obtained in Asterias amurensis by Byrne et al. [9]. The studied A. aranciacus population did not differ significantly in the male-female proportions, coinciding with previous results in other sexually reproducing asteroids (since sex-ratios can be highly biased in the case of asexual asteroids) [4,26]. The development of the A. aranciacus gonads reflected that mature and partially spawned individuals remained for an extended period of time. ...
The growth and reproductive biology of the sea star Astropecten aranciacus was investigated on the continental shelf of the northwestern Mediterranean Sea. Sea stars were captured monthly in two bathymetric ranges (5-30 and 50-150 m) between November 2009 and October 2012. Bathymetric segregation by size in A. aranciacus was detected: small individuals inhabit shallow areas (5-30 m), while large individuals inhabit deeper areas of the continental shelf (50-150 m). Recruitment was recorded twice nearshore but no recruitment was detected offshore during the whole study period. Three cohorts were identified in each bathymetric range and growth rates were estimated. A. aranciacus population exhibited a seasonal growth pattern, being higher from June to October in the nearshore cohorts and from February to October in the offshore ones. Histology and organ indices revealed that spawning likely started in March, coinciding with the spring phytoplankton bloom and the increase in sea water temperature, and extended until June-July. Ratio between males and females was approximately 1:1 throughout the year and in both bathymetrical ranges. The size at first maturity (R50%) was estimated to be R=112 mm. A. aranciacus did not show an inverse relationship between gonad index and pyloric caeca index.
... At the Mexican south Pacific scale, López-Pérez et al. (2016), established a historical average temperature for the region of around 28°C, and an increase of up to 1.8°C above historical data during the ENSO event. An important influence of the temperature over the intensity of reproductive activity has been reported for three echinoderm species (Benítez-Villalobos and Martínez-García, 2012;Benítez-Villalobos et al., 2013 and two mollusks (Avila-Poveda, 2013;Alejo-Plata and Gómez-Márquez, 2015) in this area. This intensity in reproductive activity indicates that the increase in temperature during the warm period (May-October), reaching almost 30°C, probably acts as one of the proximate causes that determine the seasonal reproduction observed in those marine invertebrates. ...
... A temperature of 2°C above the average temperature (28°C) of the area where the population studied inhabits, promoted a larger fertilization success, coinciding with the temperature that prevails during the year's warmest periods recorded in the study area (between May and September) when a number of marine invertebrates show a more intense reproductive activity (Benítez-Villalobos and Martínez-García, 2012;Benítez-Villalobos et al. 2013Avila-Poveda, 2013;Alejo-Plata and Gómez-Márquez, 2015). In contrast, the temperature of 32°C Fig. 4. Percentage ( ± SD) of developmental stages of Toxopneustes roseus achieved at every time point during the experimental period (30 h) at the three temperature treatments. ...
Toxopneustes roseus performs a key role in the eastern tropical Pacific as a strategic herbivore and bioturbation promoter. We evaluated the effect of temperature on the fertilization success, embryonic development and larval survival of T. roseus under laboratory conditions, to understand how the increase in ocean temperature could affect it in a global warming. The highest percentage of fertilization occurred in gametes that were exposed to 30 °C, and a significant negative effect of 32 °C was evidenced by the lowest percentage. There was also a deleterious effect in embryos exposed to 32 °C, resulting in an abnormal development at all the time points. The highest percentage of larval survival occurred at 30 °C, while the lowest percentage occurred at 32 °C. The results suggest that T. roseus probably lives near its upper thermal limit, and future ocean warming could threaten the permanence of the species in the eastern tropical Pacific, or at least lead to contraction or fragmentation of its range limits. Therefore if sea temperature rises globally, it could cause the disappearance of these populations that are living at the edge of their thermal tolerance, but for other populations located in more temperate latitudes, it could propitiate favorable conditions for fertilization and survival of embryos and larvae.
... A temperature of 28°C was considered as the control, as it is the historical average seawater temperature in the study area. A temperature of 30°C was considered as the summer temperature, when the most intense reproductive activity has been observed for several marine invertebrates in the study area (Avila-Poveda, 2013;Benítez-Villalobos et al., 2012, 2013, 2015. A temperature of 32°C (an increase of 4°C above the average) was considered as the most extreme scenario predicted by the IPCC for the region by 2100, where average sea temperature is expected to increase by 1.6-4°C, depending on geographic region (Brierley and Kingsford, 2009;Meinshausen et al., 2011;IPCC, 2022). ...
Environmental temperature is one of the most significant factors influencing the developmental rate and survival of embryos and larvae of many marine animals, including polychaetes. The aim of this study was to experimentally evaluate the effect of temperature increase on the embryonic development and larval survival of Spirobranchus incrassatus and S. cf. corniculatus. Adult worms of both species were collected from the western margin of the Gulf of Tehuantepec, Mexico. Embryos and larvae were obtained from these worms and exposed to four temperature treatments (28, 30, 32 and 34°C). The optimal temperatures for embryonic development of S. incrassatus and S. cf. corniculatus were 30 and 28°C, respectively. For both species, the maximum critical temperature was 32°C and the lethal temperature was 34°C. The embryonic stages of S. cf. corniculatus were most negatively affected by elevated temperatures. Larval survivorship of S. incrassatus and S. cf. corniculatus was higher at 30°C and 28°C (76.2±2.8%; 72.6±4.2%) and lower at 34°C (28.9±2.6%; 26.3±2.9%), respectively. These results suggest that S. cf. corniculatus has the lowest thermal tolerance. Both Spirobranchus species already live near their upper limit of thermal tolerance in the study region (30°C). In the near future, under a global warming scenario, the distribution of both species could be modified, causing a loss of biodiversity, changes in the trophic chain, and alterations in the water column, such as excess organic matter.
... Toxopneustes roseus is another typical species of sea urchin, which has a wide latitudinal distribution throughout the tropical eastern Pacific and co-inhabits with other species of sea urchins and echinoderms that have a similar distribution and in which hermaphroditism has not been reported 40,[55][56][57] . Regarding its population density, T. roseus is not considered among the most abundant species in the study area and its densities are relatively low (between 0.04 and 1.2 ind.m 2 ). ...
Trioecy is a sexual system that consists of the co-occurrence of females, males and hermaphrodites in a population and is common in plants; however, in animals it is uncommon and poorly understood. In echinoderms, trioecy had never been recorded until now. Frequencies of females, males, and hermaphrodites were evaluated and gametogenic development was histologically characterized in a population of Toxopneustes roseus inhabiting the Mexican Pacific. Trioecy in this population is functional and temporally stable, since the three sexes coexisted in each sampling month. The hermaphrodites presented similar gametogenic development as the females and males and participated during the spawning season, contributing to the population’s reproductive process. Trioecy is considered an evolutionarily transitory state, and it is extremely difficult to explain its presence in a species. We hypothesize that continuous ocean warming represents a threat to the survival of this population of T. roseus, since its early developmental stages, which represent a population bottleneck, are more vulnerable to high temperatures than other sea urchins inhabiting the area, while its population density is significantly lower. These conditions generate a strongly stressed environment, which is the determining factor that maintains the stability of trioecy in the species in which it has been studied.
... The bipinnarial arms were stubby and the round rudiment was a rusty brown color. This larva was collected in November, which is consistent with the spawning season of July-September reported from the Mexican tropical Pacific (Benítez-Villalobos & Martinez-Garcia, 2012). There is no other published information on the reproduction of this species. ...
As part of a project to document the diversity of larval invertebrates on both coasts of Panama, we collected and photographed 141 larval asteroids and sequenced fragments of their mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal DNA. We uncovered 10 Caribbean operational taxonomic units (OTUs) and five Pacific OTUs. We could identify six of the 15 OTUs based on >99% similarity with reference sequences in GenBank: The Pacific species Astropecten verrilli and Pentaceraster cumingi and the Caribbean species Astropecten marginatus, Astropecten antillensis, Oreaster reticulatus, and Mithrodia clavigera. Two other OTUs were placed in BINs in the Barcode of Life Database (BOLD) with unpublished sequences that were identified as Pharia pyramidata from the Pacific and Valvaster striatus, now known from the Caribbean as well as the Indo‐West Pacific. The remaining seven species appear likely to belong to Luidia, as 16S sequences from each have 87%–95% identity with various species of Luidia, and the sequences nest among species of Luidia in neighbor‐joining trees. The low diversity of asteroid larvae reflects ~10% of the diversity of adult sea stars reported from Panama, and highlights the need for broader collection efforts and improved coverage of DNA barcode reference sequences for Luidia and other soft‐bottom species.
... Reproductive cycles tend to be more synchronized with increasing distance from the equator, and seasonality becomes more pronounced (Pearse, 1968(Pearse, , 1970. Seasonality of reproduction is also synchronized to maximize the survival of spawning, exposing the larvae to more favourable conditions for development (Giese & Pearse, 1974;Benítez-Villalobos & Martínez-García, 2012;Benítez-Villalobos et al., 2015). ...
Widely distributed species such as Arbacia stellata adjust patterns of their life history according to local conditions. In the present study the reproductive cycle of this species was analysed throughout a sampling year. Gonadal development cycle, sex ratio, actual fecundity and oocyte size distribution were characterized and the relationship of these reproductive characteristics with environmental variables such as sea surface temperature, photoperiod, chlorophyll a and net primary production evaluated. Our results showed that A. stellata is a gonochoric sea urchin. Gametogenesis was classified into six stages for both sexes (immature, growth, pre-maturity I, pre-maturity II, mature and spawning) and no synchrony was observed for the gonads between individuals. The female to male ratio was close to 1:1 in most months. The gonadosomatic index (GSI) showed significant differences between sexes or months; however, the highest values were observed during spring, with positive correlation with chlorophyll a . No significant differences were observed in the maturity index (MI) between sexes, with a positive correlation with temperature but negative with chlorophyll. Actual fecundity showed wide variations throughout the year and correlation with chlorophyll a and temperature. Oocyte size distribution was unimodal and the predominant frequency was that of mature oocytes. The reproductive cycle of A. stellata has a semi-continuous pattern for both sexes and partial spawning throughout the year in the sampling site. We observed nutrient assimilation in the gonads during spring and a larger reproductive activity from late summer to early winter.
... In 2008 and 2009, similar outbreaks happened in coastal waters of Yantai and Weihai. Asterinid species have different reproductive patterns, includ- ing seasonal or continuous breeding periodicity (Carvalho and Ventura, 2002;Barker and Xu, 1991b;Byrne, 1992;Paik et al., 2005; Pastor-de- Ward et al., 2007;Mariante et al., 2010;Micael et al., 2011;Benítez-villalobos and Martínez-garcía, 2012). The dif- ferences are related to many environmental factors, including temperature, hydrodynamics, the quantity and quality of avail- able food, and photoperiod. ...
To obtain baseline information on the size distribution of individuals in the population and reproductive features of sea star Asterias amurensis, monthly surveys of the population were carried out from May to December 2010 and March to May 2015 in coastal waters off Yantai, China. Spawning period was predicted by gonad and pyloric caeca indices as well as anatomical and histological methods. In the A. amurensis population, both large individuals (>143 mm) and small ones (<42 mm) were present in all sampling months. The population size structure was driven by the appearance of big cohorts of individuals less than 55 mm from May to August. The appearance of small individuals in all months suggested a prolonged spawning period at other sites in this bay or sea stars growing slowly because of food shortage. An arm length is a good predictor to wet body weight for A. amurensis. The development of gonad was relative slow from May to September but rapidly reached a peak of 20.95 in October 2010, and then dropped remarkably, indicating its spawning lasted from October to November. The same phenomenon was found from March to May 2015, suggesting another spawning during March to May, which was also verified by the results of histologic analysis on ovary. The gonad index (GI) and pyloric caeca index (PCI) tended to show a negative relationship. Due to the poor food availability, the reproductive characteristics of sea star were most likely affected by the shellfish mariculturein Yantai coastal waters.
... Most gametogenic stages did not differ between sexes in the GI values. It has been reported that some asteroid species have higher GI values in females than in males (Carvalho & Ventura, 2002;Pastor de Ward et al., 2007;Bos, Gumanao, Alipoyo & Cardona, 2008;Benítez-Villalobos & Martínez-García, 2012) while others show higher values in males than in females (Benítez-Villalobos & Díaz-Martínez, 2010) or even no difference between the sexes (Georgiades, Temara & Holdway, 2006;Benítez-Villalobos, Díaz-Martínez & Tyler, 2007;Mariante, Lemos, Eutrópio, Castro & Gomes, 2010). ...
Energy allocation patterns during the reproductive cycle of echinoderms may be determined by the different energy requirements of the organisms. In this study, we describe the energy reserves variation in the gonads, pyloric caeca and stomach among the gametogenic stages of a population of Cosmasterias lurida from the Beagle Channel, Argentina. Adult individuals of C. lurida were collected from the subtidal zone of Ushuaia Bay during four seasonal sampling periods (August 2010 to June 2011). Indices, energy density (kJ/g ash-free dry mass) and energy content (kJ) of gonads, pyloric caeca and stomach were determined. Oocytes number and diameter were evaluated. Cosmasterias lurida had a major peak of gonadal index (GI) in mature gonads (M), with a great decrease towards the spawning (PS/PSR) and remature (RM) periods. No variation was observed in the energy density of the gonads (EDG). The energy content of the gonads (ECG) presented a similar pattern to the GI. Thus, the gonadal storage cycle can be explained through the variation in gonad mass more than in its energy density. Females had higher ECG and EDG values than males, which suggest a greater energy contribution in females during the reproductive cycle. The stomach and the pyloric caeca indices, energy density and energy content remained unaltered among the stages. The energy density of pyloric caeca (EDPC) was higher in mature males than in mature females. Likewise, the energy density of the stomach (EDS) was overall higher in males than in females. This inverse pattern between sexes in relation to the EDG may suggest a transference of energy from the pyloric caeca and stomach to gonads during maturate stage playing a storage role for reproduction.
... Therefore, species like E. thouarsii, T. roseus and P. pyramidata showed a density decrease trend from 2011 to 2013. These species are well known as active grazers of calcareous algae and algal turf, as well as by their facultative diet of sessile invertebrates such as coral polyps, bryozoans, sponges and barnacles (Paredes 2010;Benítez-Villalobos and Martínez-García 2009;Benítez-Villalobos and Abadia-Chanona 2015). In addition to a general density and richness decrease trend in mid-2013, a "groundswell" event caused fragmentation of most of the biggest branching coral colonies. ...
Echinoderms are a conspicuous assemblage associated with coral communities, which provides them with food, shelter, and nursery areas. Temporal and spatial changes in environmental conditions may modify their density and composition, which furthermore may affect the structure of the coral community. In order to identify the response of echinoderm composition to environmental fluctuations, variations in the density were evaluated at spatial and temporal levels from
2011–2014 in Islas Marietas National Park, a National
Protected Area located off the Mexican Pacific coast, which
harbors the most important coral and echinoderm community
in the region. The results showed that the species Diadema
mexicanum, Centrostephanus coronatus, and Eucidaris
thouarsii, were dominant. Differences between areas off the
islands were observed, as Isla Redonda showed the highest values (1.31 ± 0.15 in. m2, S = 7.74 ± 0.17) associated with high heterogeneity and availability of food resources. Isla Larga had the lowest density (0.89 ± 0.7 in. m2) and richness (S = 6.49 ± 0.24). This was associated with the presence of high coverage of branching corals (16.34%) which can be considered a space competitor for echinoderms. Moreover, during cold seasons, density (17.44%) and richness (12.6%)
increased, with a positive relation with the food supply. During the 2011/La Niña, a partial coral mortality resulted in the proliferation of turf and contributed to the highest abundance of grazer echinoderms. Abundance decreased during the following years, due to the loss of turf coverage. The assemblage of echinoderms maintained their species composition over the years, showing that the coral community of the
Central Mexican Pacific has a singular auto-regulatory capacity that allows their long-term maintenance in response to environmental anomalies.
Available on: http://link.springer.com/article/10.1007/s12526-016-0622-y
... Therefore, species like E. thouarsii, T. roseus and P. pyramidata showed a density decrease trend from 2011 to 2013. These species are well known as active grazers of calcareous algae and algal turf, as well as by their facultative diet of sessile invertebrates such as coral polyps, bryozoans, sponges and barnacles (Paredes 2010;Benítez-Villalobos and Martínez-García 2009;Benítez-Villalobos and Abadia-Chanona 2015). In addition to a general density and richness decrease trend in mid-2013, a "groundswell" event caused fragmentation of most of the biggest branching coral colonies. ...
... Martínez-García 2012, Benítez-Villalobos et al. 2013. ...
The chiton, Chiton (Chiton) articulatus commonly known as "dog tongue" or "sea cockroach" is collected as bait for artisanal fisheries and offered in restaurants like gourmet dish, along the Pacific coast of Mexico, so their consumption is generating a potentially exploitable fisheries and economic interest. Considering reproduction as fundamental in the life history, the economic importance of the resource and that does not have control in their consumption and marketing; studies on aspects of reproductive biology of this species are needed. The aim of this study is to contribute to the basic knowledge of C. (C) articulatus in aspects such as gonadal maturation, reproductive cycle, reproductive season and its relationship with environmental variables, sex ratio and size at maturity (Tm50%). During 2011, 32 adult chitons were monthly collected in Puerto Angel, Oaxaca. A technique for relaxation, fixation and dissection of animals was established. Were taken body measurements (total length: LT, Shell length: LC, total width: AT, Shell width: AC) and total weight (PT). By histological analysis of the gonad the maturation sequence of the female gamete was described, a method for viewing and setting of the gonad maturation stages (GMS) is proposed, and the reproductive cycle was obtained. The reproductive season was characterized with the gonadosomatic index (GSI) and the index of microscopic maturity (IMMi). The sex ratio was calculated. The TM50% were estimated considering the four measurements morphological and the body weight. The gonad of C. (C.) articulatus produces synchronously gametes and the mature oocytes have the "hull egg" characteristic of polyplacophorans. Five gonad maturation stages (GMS) were established and described: I-goniogenesis, II-development, III-mature, IV-spawning, V-rest or recovery. Although C. (C) articulatus is a total spawner and it reproduce throughout all year, the main reproductive season (maturity and spawning) occurs in the second half of the year (July to December), and coincides with the rainy season. The sex ratio during the entire sampling period was 1:1. The TM50% for both sexes was: LT 55.43 mm, LC 50.70 mm, AT 33.27 mm, AC 28.06 mm and PT 11.86 g. It is suggested that a panoramic observation of the gonad for the establishment of GMS. By using different morphometrics for estimating the Tm50% are given more options to establish minimum catch sizes, besides to facilitate data collection in the field. With these results we contribute to the basic knowledge of reproductive biology of Chiton (Chiton) articulatus, which allow proposing future regulatory measures (i.e., closed season and minimum catch size).
... Recently, the study of echinoderms in the Southern Mexican Pacific has not only focused on systematics, but also on ecology (Benítez-Villalobos, 2001;Lirman et al., 2001;Calderón-Aguilera & Reyes-Bonilla, 2006;López-Pérez et al., 2008;Zamorano & Leyte-Morales, 2005a, 2005b, bioerosion (Herrera-Escalante et al., 2005;Benítez-Villalobos et al. 2008b), reproduction (Benítez-Villalobos & Martínez-García, 2012;, and symbiosis (Granja-Fernández et al., 2013b). ...
The echinoderms of the Southern Mexican Pacific have been studied for three centuries, but discrepancies
in the nomenclature of some species have pervaded through time. The objective of this work is to present the first updated checklist of all valid species and synonyms, and a historical review of the study of the echinoderms of the Southern Mexican Pacific is also presented. The checklist is based on an exhaustive published literature search and records of specimens deposited in museum and curated reference collections. There are 162 species of echinoderms in the Southern Mexican Pacific from 96 genera, 54 families and 20 orders. The State of Guerrero presented a total of 135 species, Oaxaca 94 and Chiapas 15. We updated the list and added five new records of the species (Microphiopholis platydisca, Ophiostigma tenue, Arbacia stellata, Thyone bidentata, Chiridota rigida) for the Southern Mexican Pacific and one for the Mexican Pacific (Encope laevis). This checklist expands the number of species known for the study area; nevertheless studies suggest that still more species are yet to be discovered
... High-latitude marine ecosystems present important seasonal fluctuations (Clarke 1987;Almandoz et al. 2011). As a consequence, several environmental factors such as sea water temperature, photoperiod, water salinity, food availability, pluvial precipitation and lunar cycle have a strong influence on the reproductive cycles of echinoderms (Pearse and Eernisse 1982;Pearse et al. 1986; Bouland and Jangoux 1988;Byrne 1992;Byrne et al. 1997;Stanwell-Smith and Clarke 1998;Pearse and Bosch 2002;Benítez-Villalobos and Martínez-García 2012). Gonadal development is closely related with nutrient acquisition (Lawrence 1987a) although ingested energy must be partitioned among organism growth and maintenance as well (Lucas 1996). ...
Seasonal fluctuations in environmental factors at high-latitude marine regions have a strong influence on the reproductive cycles of echinoderms. The purposes of this study on a population of Cosmasterias lurida in the Beagle Channel are to describe the reproductive cycle through histological analyses, to characterize the pattern of gonad and somatic indices, to determine the energy content of different organs and their temporal variation and to establish the pattern of energy allocation. During the study period, from August 2010 to June 2011, four seasonal samplings were performed in the subtidal zone of Ushuaia Bay. Indices (gonad, pyloric caeca and stomach), gonadal histology, organic matter and calorimetric measurements were determined. Gametogenesis begins in February and continues until June when oocyte size increases. The gonadal maximum development and gamete releasing take place between August and December. Temporal variation of energetic reserves in gonads occurs through the variation in gonad mass, with a GI major peak and energy content during August. Stomach and pyloric caeca show their maximum energy accumulation during June, while decrease of organic matter of the body wall takes place from August to December. The population of C. lurida from Beagle Channel suggests an annual reproductive cycle with two maturation events and the influence of water temperature on maturation and releasing of gametes. Different patterns of energy allocation to gonads between sexes were observed, with a greater energy investment in females than in males. Pyloric caeca, stomach and body wall were proposed as energy reservoirs for gonadal maturation and spawning.
... At high latitudes, sea stars show a marked seasonality in reproduction (Smith and Clarke, 1998) that fades in mid-latitudes (Rubilar et al., 2005; Ventura et al., 1997 ) and is not evident in tropical species (Guzmán and Guevara, 2002). Many studies provide evidence about the relationship between reproductive cycles of sea stars and different environmental factors such as seawater temperature, day-length, pluvial precipitation and food supply (Villalobos and Martínez-García, 2012; BenítezVillalobos et al., 2007; Stanwell-Smith and Clarke, 1998; Pain, 1982a, 1982b; Tyler et al., 1984). Understanding the fluctuation of these factors is important to elucidate the coupling between reproductive patterns and the environment (Mercier and Hamel, 2009). ...
... The marked differences between dry and rainfall seasons and strong upwelling influence the biological processes of the communities at an evolutionary level, determining the seasonal reproductive patterns observed in Holo thu ria fuscocinerea and other echinoderm species in the area, such as the starfish Pharia pyramidatus (Benítez-Villalobos & Martínez- García 2012) and the brittle stars Ophiocoma aethiops and O. alexandri ). ...
The sea cucumber Holothuria fuscocinerea is among the most common holothurian species widely distributed in the Tropical Eastern Pacific Region and is becoming a potentially important fishery in Mexico. Nevertheless, there are no studies about its reproductive biology. This study analyzed several reproductive traits of H. fuscocinerea based on monthly time-series samples taken from April 2008 to March 2009 at La Entrega Bay, Oaxaca, in the Mexican tropical Pacific. Sex ratio, gonad development stages (GDS), reproductive cycle, diameter and distribution of oocytes, and fecundity were determined. Reproductive indices (the gonadosomatic index [GSI] and maturity index [MI]) were calculated, and their relationship with some environmental factors (temperature, rainfall, salinity, and pH) was evaluated. H. fuscocinerea is a gonochoric holothuroid, and its annual ratio of males to females was not significantly different from 1:1. Four GDS (i.e. gametogenesis, mature, spawning, post-spawning) as well as one period of gonadal recovery, which is ‘sexually undifferentiated’, were established. Spawning occurred from June to October in females and from April to September in males. Post-spawning of females and males and recovery stages coincided from October to January. Mean fecundity was 2.9 ± 2.8 million oocytes per female, with ovaries exclusively comprised of vitellogenic oocytes from June to September. GSI and MI values showed similar variations in accordance with the reproductive cycle, and GSI showed a relationship with rainfall season. Seasonal rainfall may act as a cause of the seasonal reproductive pattern observed in H. fuscocinerea.
This work aims to describe for the first time the reproductive biology of the red starfish Echinaster sepositus at the western region of Algeria (Mostaganem). The population of E. sepositus is characterized by a sex ratio of 1:2 (female: male). The relation between arm length and wet body weight indicate a negative allometric growth. Histological study reveals six stages of sexual maturity in females (I: development; II: premature ; III: mature; IV: partly spawned; V: post-spawning; VI: recovery) and five stages in males (I: development; II: premature ; III: mature; V: post-spawning; VI: recovery). The gonadosomatic index shows that there is only one spawning period per year, which happens from July to November. The gonadal maturity and gametogenesis of E. sepositus are correlated with the environmental factors namely temperature and photoperiod. ARTICLE HISTORY
To assess the variation of sea star (Asteroidea) populations in the Northern Gulf of California and look for evidence of sea star ulcerative lesions, counts of sea star species were recorded in 2019 using a standard belt-transect technique of 30 m2. During surveys, scuba divers also measured sea stars' diameter and examined them for ulcerative lesions. Ulcerative lesions were noted on Phataria unifascialis only. To verify changes in abundance and size of the two most abundant species, P. unifascialis and Pharia pyramidata, historical data from 2009, 2010, and 2016 were used as comparison and using the same methodology. To evaluate differences in abundance or diameter in sea star species over time, analysis of variance tests (ANOVA) were used. We found a significant reduction in diameter for the species P. unifascialis and P. pyramidata over time (<0.0001), but only P. unifascialis also showed a significant decrease in abundance (P=0.018). The decrease in diameter recorded for these two species, along with the signs of ulcerative lesions found on one of them in 2019, suggest that a potential mortality event occurred and, as a result, new younger (i.e., smaller) recruits could be recovering the population. These results highlight the importance of population monitoring to understand complex reef community dynamics.
Reproductive studies of an intertidal free-spawning population of Chiton articulatus (Mollusca: Polyplacophora) from Puerto Angel, Oaxaca, Mexico were undertaken during 2011. We used gonad histology and gonadal indices to assess the relative gonad expenditure of the sexes (RGES) and other reproductive traits, accounting for individual and seasonal variation within this population. At this location, C. articulatus is gonochoric, without sexual dimorphism, except internally by gonad colour (testis is ‘salmon’ coloured and ovary olive green). Annual and monthly sex ratios (m/f) do not differ significantly from 1:1. Highest population-level gonadosomatic index (GSI) corresponded to maximum (peak) ripe stage (i.e. maximum gonad investment), with a first peak in May with a high value (8.4 ± 0.5) and a second peak during August-September with a lower value (4.7 ± 0.3). GSI fluctuated throughout year implying that gonad expenditure may be seasonally constrained, but with overall synchrony between sexes of ripe and spawning stages. July to December was the main reproductive season with some facultative spawning occurring off-season. Ripe and spawning RGES did not differ between sexes, suggesting that either sperm competition is intense and/or that sperm limitation is high. Early spawning individuals may quickly replenish their gametes for a second phase of gamete release later. Abbreviations: RGES: relative gonad expenditure of the sexes; GSI: gonadosomatic index; GDS: gonad developmental stages; MiMI: microscopic maturity index; SST: sea-surface temperature. © 2018
Resumen El Parque Nacional Islas Marietas (PNIM) es un área natural protegida, la cual alberga una alta biodiversidad y provee de servicios ecosistémicos de soporte, regulación y suministro. En los últimos años, esta área ha generado un interés turístico y en consecuencia altos niveles de visita, provocando una degradación en la comunidad coralina y un efecto negativo en los organismos asociados. Debido a su aspecto y coloración, los equinodermos de PNIM son considerados organismos carismáticos, por lo que es común que estos sean manipulados por los usuarios del parque, estas malas prácticas pueden generarles estrés o inclusive la muerte. La presente revisión tiene el fin de contribuir al programa de conservación y manejo del parque dentro del sub-programa de educación, mediante un material de difusión que incluye las generalidades biológicas y ecológicas de los equinodermos conspicuos del PNIM, así como fichas que permiten la identificación visual de las especies sin necesidad de manipulación. Este material promoverá el conocimiento de los equinodermos, su importancia en los procesos ecológicos y su valor como elementos paisajísticos dentro del PNIM, fomentando una conciencia de respeto a la naturaleza en los usuarios del parque y con el fin de contribuir a la conservación de los recursos de esta Área Marina Protegida.
Sedentary broadcast‐spawning marine invertebrates, which release both eggs and sperm into the water for fertilization, are of special interest for sexual selection studies. They provide unique insight into the early stages of the evolutionary succession leading to the often‐intense operation of both pre‐ and post‐mating sexual selection in mobile gonochorists. Since they are sessile or only weakly mobile, adults can interact only to a limited extent with other adults and with their own fertilized offspring. They are consequently subject mainly to selection on gamete production and gamete success, and so high gonad expenditure is expected in both sexes. We review literature on gonadosomatic index (GSI; the proportion of body tissue devoted to gamete production) of gonochoristic broadcast spawners, which we use as a proxy for gonad expenditure. We show that such taxa most often have a high GSI that is approximately equal in both sexes. When GSI is asymmetric, female GSI usually exceeds male GSI, at least in echinoderms (the majority of species recorded). Intriguingly, though, higher male GSI also occurs in some species and appears more common than female‐biased GSI in certain orders of gastropod molluscs. Our limited data also suggest that higher male GSI may be the prevalent pattern in sperm casters (where only males release gametes).
We explore how selection might have shaped these patterns using game theoretic models for gonad expenditure that consider possible trade‐offs with ( i ) somatic maintenance or ( ii ) growth, while also considering sperm competition, sperm limitation, and polyspermy. Our models of the trade‐off between somatic tissue (which increases survival) and gonad (which increases reproductive success) predict that GSI should be equal for the two sexes when sperm competition is intense, as is probably common in broadcast spawners due to synchronous spawning in aggregations. Higher female GSI occurs under low sperm competition. Sperm limitation appears unlikely to alter these conclusions qualitatively, but can also act as a force to keep male GSI high, and close to that of females. Polyspermy can act to reduce male GSI. Higher male than female GSI is predicted to be less common (as observed in the data), but can occur when ova/ovaries are sufficiently more resource‐intensive to produce than sperm/testes, for which some evidence exists. We also show that sex‐specific trade‐offs between gonads and growth can generate different life‐history strategies for males and females, with males beginning reproduction earlier. This could lead to apparently higher male GSI in empirical studies if immature females are included in calculations of mean GSI. The existence of higher male GSI nonetheless remains somewhat problematic and requires further investigation.
When sperm limitation is low, we suggest that the natural logarithm of the male/female GSI ratio may be a suitable index for sperm competition level in broadcast spawners, and that this may also be considered as an index for internally fertilizing taxa.
Studies of pre-spawning crown-of-thorns starfish Acanthaster (COTS) collected from the Great Barrier Reef showed average female gonad mass of 16 % (±8 s.d.) and for males 12 % (±6 s.d.). In females up to 34 % of the body mass could be devoted to gonad. Based on these data, we also derived relationships between diameter gonad weight and reproductive output for both male and female starfish. Due to the large average size of individuals in this study (39.2 ± 0.3 cm diameter), the potential oocyte production of females was between 29 and 38 million eggs per season for average size starfish. The highest oocyte production was estimated to be >100 million oocytes, which is the highest ever recorded for an individual female starfish. These relationships imply that the largest Acanthaster reported may have fecundities greater than 200 million eggs per season. The gonad mass of male starfish is similarly high, and in combination with measured concentrations of sperm exuded from the gonopore (5.2 × 1010 ml−1) the sperm output of an average sized male is estimated to be 1.1 × 1013 sperm. This high level of sperm production may be a key factor allowing this species to sustain itself and even initiate outbreaks at low population densities. We suggest that management targets for maintaining COTS at pre-outbreak thresholds should take account of starfish size as well as starfish density, especially given extreme reproductive potential of large starfish in pre-outbreak populations.
The brown sea cucumber Isostichopus fuscus (Ludwig, 1875) has been subjected to strong fishing pressure and is currently considered an endangered species by the IUCN Red List of Threatened Species. Spatial and temporal variations in density were analysed and population parameters of I. fuscus were estimated in three localities of the Southern Mexican Pacific. Density was estimated using circular transects covering a 300 m2 area in each locality. Body length and weight were also measured. The mean density was 0.018 ± 0.013 individuals·m−2, and was statistically significantly lower during summer. The mean length and weight were 22.4 ± 3.8 cm and 396 ± 130 g, respectively, and statistically significant differences were found among localities. The weight–length relationship was W = 0.28·L1.32 and the mean relative condition index (Kn) = 1.04 ± 0.31. The von Bertalanffy growth equation was Lt = 38.7·(1–exp(−0.4·t)). The lowest values of length, weight and age were found at Dos Hermanas, suggesting that this locality could be favorable for the settlement of larvae and recruitment and growth of juveniles. The present study is the second to estimate densities of I. fuscus and the first one to publish data on size structure and growth for the population at Bahias de Huatulco. The densities were so low in the three sampled localities that none of them would be able to support a fishery, even under a sustainable management scheme. The information collected in the present study could be helpful for management programs of the Huatulco National Park, as all the data used for these currently come mainly from the populations of I. fuscus in the Gulf of California.
Bivalves living in large aggregations of individuals (reefs or beds), such as mussels,
clams, cockles and some high trophic predators such as sea stars, play an essential
ecological role in the structure, integrity, stability, and diversity of the biological
communities; being usually considered as keystone species. Their disappearance or
decline could lead to disproportionate effects in their communities, even affecting the
survival of other species. Although keystone species are crucial for maintaining the
Earth biodiversity, often their study has not taken enough attention. The main aim of
this Doctoral Thesis was to study the ecology of some keystone invertebrates inhabiting
shallow soft bottom communities of the Maresme coast (Northwestern Mediterranean
Sea). The results enhance the knowledge of the smooth clam (Callista chione) and also
of its potential predators, several species of sea stars (Astropecten spp.) co-occurring in
the area. But at the same time, our findings help to understand their trophic interactions,
the status of their populations and propose guidelines for their conservation. Maresme
coast is close to Barcelona and it has concentrated historically a high anthropogenic
pressure that has altered and modified its environment. Our results have showed the
critical status of the smooth clam bed as a consequence of the combination of different
human coastal uses: sand dredging and clam fisheries. These anthropogenic pressures
have also led to significant changes in Astropecten populations. A. aranciacus has been
shown to be the most vulnerable, and consequently the most affected, to the extent that
its population suffers an important and worrying decline. Moreover, A. aranciacus
reproductive cycle, growth and depth segregation between size classes along the
continental shelf have been described for the first time. Our results have documented
Astropecten species niche segregation, which allow them to co-occur within a biological
community scale, without compete for the same available recourses. Sea stars showed a
partitioning of the prey (species) and microhabitats in the Maresme coast. This Doctoral
Thesis aims to provide a valuable background to improve the conservation of these
keystone invertebrates, as well as to promote the sustainable exploitation of shellfish.
Diadema mexicanum is a common inhabitant of the Mexican Pacific coast and a key species for coral reefs dynamics. Several reproductive traits of D. mexicanum throughout one year at La Entrega Bay, Oaxaca (15°44′N), in the Mexican tropical Pacific, were analyzed. Maturity index or microscopic maturity index “MI” was calculated. Annual ratio of males to females (1:1) was not significantly different. Five gonad development stages “GDS” (i.e. development, mature, spawning, post-spawning, nutritive) were recognized. The nutritive stage was noticeably later to post-spawning. High values of gonadosomatic index “GSI” in December 2008 and February/March 2009 did not correspond to maturity but to the nutritive stage. MI values ratified the periodicity of each GDS and spawning preparedness. MI was a better descriptor than GSI for reproductive season of D. mexicanum, and probably for all sea urchins exhibiting the nutritive stage. D. mexicanum has a single annual reproductive season (maturity/spawning) from April to October, similar to the population of Panama (9°00′N), without a second season, as proposed previously for the population of Colima, Mexico (19°10′N). Previous disparities in its reproductive season reflect differences of the environments it inhabits, rather than an effect of the latitudinal gradient in the tropical region.
The reproductive biology of the massive coral Pavona gigantea has been studied along Mexico’s Pacific coast, but basic aspects such as its relation to local environmental variables and its variation on a mesoscale level have not been addressed. The reproductive cycle of P. gigantea was monitored monthly over a two-year period (2010–2012) at four sites along the coast of Oaxaca (southwestern Mexico). Except for one hermaphroditic colony, P. gigantea was gonochoric and exhibited asynchronous development. The data suggest that, in the study area, the species may reproduce seasonally, with minor interannual differences (May–September 2010, April–August 2011, April–May 2012). There were spatial and temporal variations in the percentage of reproductively active colonies and the presence of mature sex cells. A multiple regression analysis revealed that the percentage of reproductively active colonies was significantly explained (69.6%) by mesoscale variations in environmental variables such as sea surface temperature, photosynthetically active radiation, diffuse attenuation coefficient, percentage of lunar illumination, and photoperiod, the latter being the most relevant variable in the model. The data suggest that temporal mesoscale variations can exert a meaningful influence on coral reproduction in the study area
Geographical implications of seasonal reproduction in the bat star Asterina stellifera, Journal of Sea Research (2013), doi: 10.1016/j.seares.2013.05.006 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The reproductive biology of Ophiocoma aethiops and O. alexandri was analyzed based on monthly time-series samples from May 2009 to April 2010 at Estacahuite Bay, Oaxaca, in the Mexican tropical Pacific Ocean. We evaluated the relationship between the reproductive biology of both species and variations of sea-bottom temperature, salinity, pluvial precipitation, photoperiod (light hours) and chlorophyll. Sex ratio, gonadosomatic index (GSI), actual fecundity and oocyte size were determined. Monthly variations of the environmental factors were compared with variations of GSI. Both species are gonochoric ophiuroids and the ratio of males to females (1:1) was not significantly different throughout the year. There were significant differences in GSI values between the 2 species, but temporal variation patterns were similar. Gametogenesis showed synchrony among males and females and 4 stages were recognized for both sexes. Spawning occurred in females of O. aethiops from May to November and from April to December in O. alexandri. Main spawning for males of both species occurred from May to December, although there was always availability of mature spermatozoa. Mean oocyte size was 32 to 58 µm for O. alexandri and 47 to 63 µm for O. aethiops. Mean ± SD fecundity was 3.03 ± 1.72 million vitellogenic oocytes per female for O. aethiops and 1.61 ± 0.99 million for O. alexandri. The reproductive patterns of O. aethiops and O. alexandri are influenced by the local oceanic dynamics, as has been reported for other echinoderm species in the area, but they also have a high genetic (endogenous) element, because the observed patterns resemble those determined for the Panamian populations of these 2 species.
Normal reproductive charateristics in echinoderms include non-maternal nutritions with a planktonic feeding developmental state, sexual reproduction with gonochorism, seasonal reproduction, and no protection of young by secondary metabolites. Deviant reproductive characteristics include maternal nutrition of the developmental stage that may be planktonic, demersal, or brooded; hermaphroditic sexual reproduction; intermittent or continuous low-level reproduction; protection of young by secondary metabolites; and asexual reproduction. We tested the hypothesis that stress, which causes a decrease in capacity for production, was a factor responsible for deviant reproductive characteristics by comparing taxa from the subphylum to species levels. In the examples used, deviant reproduction occurred in the taxa for which stress could be predicted. Although other factors undoubtably affect reproductive characteristics, the analysis indicates that stress must be considered an important one.
The common Antarctic sea star Odontaster validus spawns in mid-winter, following a long period of gametogenesis. In a 2-year experiment at McMurdo Sound where sea temperature remains at freezing year round, we found that gametogenesis in sea stars kept on photoperiods 6 months out of phase with ambient (constant light in winter, constant dark in summer) had, within a year, switched to 6 months out of phase with stars kept on an ambient photoperiod or collected from the field. Gametogenesis in sea stars kept in constant light or on a 12 h light: 12 h dark photoperiod appeared to be maintained more or less continuously; photoperiods of 12 h or more apparently stimulate gametogenesis. In contrast, gametogenesis in sea stars kept in constant darkness was the same as in sea stars kept on an ambient photoperiod or collected from the field, indicative of an underlying circannual rhythm similar to that known for the NE Pacific sea star Pisaster ochraceus. Such a rhythm could maintain gametogenic synchrony among different populations with different light regimes, including those in deeper water where light is very dim or absent. If so, the rhythm would need to be set in larvae when they are near the sea surface in the summer.
Individuals of the sea star genus Leptasterias from the Monterey Peninsula, California, were maintained for 34 months under two contrasting regimes of seasonally changing photoperiod. In one regime the lights turned on and off in phase with local sunrise and sunset; in the other the daily photoperiod was kept 6 months out of phase with ambient photoperiods. Annual cycles of feeding, gametogenesis, and embryo brooding of the out-of-phase animals were all shifted out of phase with respect to those of the in-phase animals. These small, relatively hardy sea stars appear well suited for more detailed analyses of photoperiodism in asteroids.
Individuals of the sea star Asterias vulgaris from New Hampshire were maintained under two contrasting regimes of seasonally changing photoperiod. In one regime the lights turned on and off in phase with local sunrise and sunset; in the other, the daily photoperiod was kept 6 months out of phase with ambient photo- period. When dissected after being maintained for 18 months, the gametogenic condition of the out-of-phase animals was found to be 6 months out of phase with that of the in-phase animals. This experiment demonstrates that photoperiodic regulation of reproduction is important even in marine animals that normally experience marked seasonal changes in sea temperature.
The reproductive biology of the North Atlantic asteroid Henricia abyssicola is determined in time series samples taken from 1250 to 1900 m depth in the Porcupine Seabight (NE Atlantic). The male-female ratio, gonadosomatic index (GI), pyloric caecum index (PCI), fecundity and oocyte size distribution were determined and the results were corroborated by histological examination of the gonads. This species is a gonochoric asteroid and the male-female ratio did not differ significantly from the equality. Oogenesis was asynchronous. The previtellogenic oocytes grow to a size of ~230 μm before undergoing vitellogenesis.
Maximum oocyte size was ~970 μm. The ovary volume was mainly occupied by large vitellogenic oocytes (400–500 μm) at any time. There were no seasonal variations in GI, PCI and fecundity. There were, however, variations in the production of vitellogenic oocytes of H. abyssicola superimposed on the continuous reproduction. We suggest that H. abyssicola makes use of the energy source provided by the deposition of phytodetritus by storing it in the developing oocytes and that it might have the benefit of a facultative planktotrophic larva.
The starfish Cosmasterias lurida was sampled from the pier piles of Almirante Storni in the Golfo Nuevo, northern Patagonia, from November 2001 to November
2003. In this anthropogenically modified site there is an unusually abundant food supply of mussels and large aggregations
of starfishes. The reproductive cycle was studied by organ indices and histological examination of gonads. The highest gonad
index (GI) values were found in the summer (February–March), followed by a drop in GI values, indicating spawning. Histological
analyses indicated that gametogenesis takes place from June to January, sexual maturity occurred during the summer and spawning
occurred in April. The GI and pyloric caeca index (PCI) tended to have an inverse relationship, but this was only statistically
significant in males. However, biochemical analyses of the starfish indicated no transfer of nutrients between pyloric caeca
and gonads in either sex. In fact, simultaneous accumulation of carbohydrates was found in the pyloric caeca and gonads of
both sexes.
A photoperiod regime 6 mo out of phase between December 1978 and August 1980 resulted in gametogenesis, gonadal growth, and spawning in laboratory-maintained sea stars [Pisaster ochraceus (Brandt)] 6 mo out of phase with individuals in the field or laboratory on normal celestial photoperiods at Santa Cruz, California (USA). The seasonal fluctuation of pyloric cecum size also was shifted when the sea stars were held on the out-of-phase photoperiod regime. Phase shift of all these events was evident within 6 to 9 mo. Long daylengths (or short nightlengths) in spring and summer apparently synchronize or entrain the initiaion of gametogenesis and gonadal growth in fall.
Sexual and asexual reproduction of the fissiparous starfish Allostichaster capensis were examined for 24months at Baha Kaiser, Golfo Nuevo, Chubut, Argentina. Gonad indices revealed an annual reproductive cycle, with peak development occurring in late winter (August). Spawning occurred in spring (September). Pyloric caeca indices displayed a clear annual cycle and a reciprocal relationship with gonad indices, showing the storage function of pyloric caeca. The starfish population appears to be largely maintained by fission, as only two females were found. A. capensis also showed an annual cycle of fission, with the highest frequency in spring and summer (from November to January), just after spawning. Incidence of fission was correlated with environmental factors such as photoperiod, seawater temperature, and salinity.
1. Four species of Indo-Pacific echinoderms, the echinoidsDiadema setosum andEchinometra mathaei, the asteroidLinckia laevigata and the holothuroidHolothuria atra, are reproductively active and spawn more or less continuously, when they occur near the equator.
2. Gametogenesis is synchronous among individuals ofD. setosum, and spawning occurs rhythmically, probably more or less monthly, during the spawning period. This spawning rhythm does not
seem to be related to lunar phases as previously reported. When further than 10–15° latitude from the equator, reproductive
activity becomes more and more restricted, until at about 30° latitude the spawning period is limited to the summer months.
3. Gametogenesis is asynchronous among individuals ofE. mathaei, L. laevigata andH. atra, and different individuals spawn at different times during the spawning periods. Some individuals ofE. mathaei are reproductively active at all times of the year throughout most of its distribution, except when north of about 27° N.
latitude when reproductive activity is limited to the summer months.
4. Sea temperature seems to be important in regulating the reproductive periodicities of at least two of the species.D. setosum is reproductively active when the temperatures are above about 25° C., andE. mathaei is reproductively active when the temperatures are above about 18–20° C.
The Phylum Echinodermata, comprising approximately 7,000 living species, and 13,000 fossil species, is epitomized by the familiar sea star, a universal symbol of the marine realm. This distinctive group of animals may be briefly defined as possessing a skeleton of calcium carbonate in the form of calcite; a unique water-vascular system which mediates feeding, locomotion, and other functions; and a more or less conspicuous five-part radial symmetry. A closer look at some extant echinoderms will show that some taxa of sea cucumbers lack calcite in their body walls, some taxa of sea stars have “outgrown” five-part symmetry and may have 50 or more arms, and many echinoderms show a more or less conspicuous bilateral symmetry superimposed upon a radial pattern. Fossil echinoderms can be even more puzzling, for some are decidedly asymmetrical, and others may lack evidence of a water-vascular system. Perhaps the only truly reliable taxonomic character of the phylum is that its members today are restricted to the marine realm.
Pyloric caeca were removed through the raytips of sea stars, Pisaster giganteus (Stimpson), beginning their seasonal period of gonad growth. Four months later their feeding rate, gonad growth, and gametogenic activity were lower than those of intact animals, while body growth rate remained the same. Removal of only the raytips also depressed feeding rate and gonad growth. When sea stars were starved, gonad growth and gametogenic activity were lower in animals without pyloric caeca, but body weight loss was the same as in intact animals. We conclude that when food is abundant, materials are utilized to enhance somatic and gonad growth. With decreasing reserves, due either to reduced food intake and/or pyloric caecum removal, somatic maintenance and growth have priority over gonad growth in material and energy allocation. Such a pattern of resource allocation is appropriate for long-lived iteroparous animals, such as these sea stars.
To assess sex differences in reproductive effort, we examined the biochemical composition and energetic content of the principal body components of the broadcast spawning sea star Asterias vulgaris in the Mingan Islands in the northern Gulf of St. Lawrence, eastern Canada. The body wall was the most stable body component, showing no variations in mass or in lipid and protein content (and total energetic content) between sexes or during spawning. Patterns in the gonads differed between sexes and with spawning. The lipid, protein and carbohydrate content of the ovary dropped during spawning, while only the protein content of the testis decreased significantly. Reproductive effort, expressed as loss of energy in the gonads during spawning for an individual weighing 10 g in underwater mass (8.2 cm in radius), was six times greater in females (49.5 kJ) than males (7.9 kJ). The energetic content of the pyloric caeca also decreased during spawning, by 17.7 kJ in females and 21.5 kJ in males, mainly due to a decrease in lipids. If this decrease is included as reproductive effort, it lessens the gender difference. The caecum decrease possibly represented expenditures due to formation of aggregations or the expulsion of gametes during spawning. Effectively, we observed aggregations during a massive spawning in this population. The sex ratio did not differ from 1:1 in all size classes sampled. This suggests that, unless males suffer higher mortality, females manage to allocate as much energy to somatic growth as males, possibly by feeding at higher rates to compensate for their higher reproductive effort. Stomach protein content tended to be higher in females than males and may indicate greater muscular development to facilitate digestion.
The annual reproductive cycle of the New Zealand starfish Stichaster australis (Verrill) was determined at Maori Bay on the west coast of Auckland. S. australis has a clearly defined summer breeding season, closely repeated from year to year. Changes in the gonad shown by histological sections confirmed this cycle.S. australis juveniles reared in the laboratory were maintained on Mesophyllum insigne (Foslie) Adey substrata and the growth rates and feeding behaviour of individual starfish were determined. Settlement on the shore was from May to July each year. When the time of spawning is considered this implies a planktotrophic larval life of ≈ 6 months. This is considerably longer than laboratory studies on larval development would suggest.Growth of yearly settlement cohorts on a nursery site on the shore used in conjunction with laboratory results gave a fairly clear picture of growth after settlement. Growth rates followed a typical sigmoid curve, growth being slow initially and becoming more rapid later. The numbers of juveniles recruited to nursery areas vary from year to year but mortality following settlement appears to be low. It was found that juvenile Stichaster australis graze Mesophyllum insigne exclusively until they reach ≈ 0.8 cm in diameter (7–8 months old) when they may occasionally predate juvenile Perna canaliculus (Gmelin). The incidence of carnivorous feeding gradually increases until juveniles are ≈ 2.0–2.5 cm in diameter (15–18 months old) by which time they are exclusively carnivorous on small P. canaliculus. As growth continues juvenile starfish gradually migrate from nursery areas to adjacent reefs where there are dense beds of adult P. canaliculus. Starfish of this species become sexually mature when they reach ≈ 5–8 cm in diameter.
Annual reproductive cycles and related changes in the pyloric caeca of the common New Zealand asterinid, Patiriella regularis (Verrill) were followed for sixteen months, in three geographically separated populations. These separate sub-populations showed marked differences in animal size and abundance and in reproductive development. The reproductive cycle was more clearly defined than in other asterinids studied and spawning occurred in summer (local) from January to March. The major reproductive difference between sub-populations was that the reproductive potential in two areas was more than twice that of the third. The cycle of the pyloric caeca index was pronounced in two of three sub-populations and bore an approximately inverse relationship to the reproductive cycle. In the area of low reproductive potential the pyloric caeca showed little fluctuation in size throughout the year. In order to test the contention that the reproductive potential is influenced by available food supplies a series of laboratory experiments were designed to run concurrently with the field studies. A representative sample of Patiriella taken from the area of low reproductive potential and raised for 11 months on crabs, showed reproductive potentials higher than any encountered in the field study areas at the same time, just before spawning. It is concluded that in Patiriella regularis the presence of stored food reserves in the pyloric caeca during the winter months is essential for good gonad development. Where such food reserves are absent due to shortage of suitable food in the habitat, reproductive potentials are low.
1.1. A population of Echinaster was sampled at intervals to measure organ indices, free amino acids (FAA), tissue protein amino acids and environmental parameters.2.2. A nutritional reproductive cycle was observed in which digestive glands peaked in size in early winter and gonads in spring.3.3. High levels of FAA build up in digestive glands in early fall and then decrease as FAA increase in gonads (especially males). After spawning both organs are FAA depleted. This cycle does not correlate with salinity.4.4. While different amino acids are rather uniformly represented in tissue proteins, glycine accounts for most of the measured FAA.5.5. The trends and patterns observed lead to the conclusion that FAA function primarily in the reproductive process, especially as a store for amino nitrogen over the winter period.
Annual reproductive and storage cycles of the asteroid Oreaster reticulatus (L.) were followed by organ index methods in populations from St. Croix in the U.S. Virgin Islands, and Carriacou and Union Island in the Grenadines. The periodicity of these cycles and their inverse relationship were similar among populations, but phase and amplitude varied. Gonad growth was activated in the spring (February to March) and progressed until spawning occurred in late summer or fall (July to October). The pyloric caeca increased in size during the quiescent phase of the gonad cycle (November to January), then decreased with increasing reproductive development to a minimum coincident with the spawning period. Reproductive development and spawning were more synchronous in the St. Croix populations than in those of the Grenadines. The inverse relationship between the storage and reproductive cycles indicated that gonadal development was subsidized by nutrient reserves previously accumulated in the pyloric caeca. Marked differences in storage and reproductive capacity among populations in the same geographic locality are attributed to differences in the quality and/or quantity of available food resources.
1. The Southern Ocean is a large‐scale, relatively homogeneous upwelling ecosystem whose phytoplankton apparently grows suboptimally over much of its area. By contrast there is a wide variety of freshwater habitats in the Antarctic and in some of these phytoplankton growth efficiency is very high. The two habitats share similar temperature and irradiance regimes, but differ markedly in availability of inorganic nutrients, in grazing pressure and in the time‐ and space‐scales on which various physical processes act.
2. Concentrations of inorganic nutrients in the marine ecosystem have been represented as being in excess of phytoplankton requirements, but the ionic composition of some nutrient pools may not conform to phytoplankton preferences.
3. Nutrient‐limitation determines phytoplankton production in Antarctic lakes and gives rise to gross differences between lakes.
4. Irradiance in the water column varies greatly over the year in both marine and freshwater ecosystems. Most algae are shade‐adapted, with the ability to utilize low irradiance but with sub‐optimal response to high irradiance. However, local phytoplankton maxima may attain very high carbon fixation and growth rates.
5. Consistently low temperatures characterize both systems. Their effects on photo‐synthetic carbon uptake mirror shade‐adaptation. Division rates of marine phytoplankton may however be very much higher than predicted for ambient temperatures.
6. Vertical mixing is important in both ecosystems and influences the environment experienced by phytoplankton cells. This appears to have little effect on the average performance of phytoplankton in the strongly mixed surface water column of the Southern Ocean, where the mixed depth may exceed 100 m. This can be related partly to the shade‐adapted photosynthetic response. Euphotic depths range from 20 to 100 m.
7. Strong vertical mixing under ice‐free conditions in lakes may maximize photosynthetic efficiency, whilst distinct vertical stratification in permanently ice‐covered lakes gives rise to segregation of nutrient uptake and regeneration.
8. Physical removal of phytoplankton biomass by grazing is locally important in the Southern Ocean, in contrast to the estimated mean mesoscale impact of grazing. Vertical sedimentation losses appear important in the context of mixing depth and generation time, and may be modified by vertical circulation of water.
9. Loss of phytoplankton biomass from lakes during the ice‐free period is dominated by physical removal via the lake outflow. Grazing is generally unimportant, except where larvae of otherwise nektobenthic zooplankton hatch in synchrony with a phytoplankton maximum. Sedimentation is important under ice‐cover.
We analysed the reproductive biology of the asteroid species Styracaster elongatus based on time-series samples from a 5000-m-deep site on the Porcupine Abyssal Plain (N.E. Atlantic). The ratio of males to females, the gonadosomatic index (GI), and pyloric caecum index (PCI) were determined and the results were corroborated by histological examination of the gonads. Fecundity and oocyte size distribution were determined by histological and image analyses. Styracaster elongatus is a gonochoric asteroid and the ratio of males to females was not significantly different throughout the year. Oogenesis was asynchronous. The previtellogenic oocytes grew to a size of ~230 μm before undergoing vitellogenesis. Maximum oocyte size was ~620 μm. The ovary volume was mainly occupied by small previtellogenic oocytes (100-150 μm) at any one time. Mean GI was 6.38±3.30 for females and 9.04±4.1 for males. Mean PCI was 7.44±1.66 for females and 7.66±1.46 for males. Mean fecundity was 16373±5988 oocites per female. There were no seasonal variations in GI and fecundity. There was evidence of a pyiloric caecum seasonal development for females and males. For S. elongatus there is no direct relationship among seasonal primary production at the surface and production of vitellogenic oocytes. Nevertheless, this species takes advantage of the pulse of phytodetritus to the seabed by increasing the storage of nutrients in the pyloric caecum in order to maintain a constant production of eggs and sperm.
Examination of the reproductive biology of three closely related sympatric astropectinid asteroidshas revealed two distinct reproductive strategies. In Plutonaster bifrons and Dytaster insignis the gonads are serially arranged and open at gonopores located at the tip of genital papillae found on the dorsal arm surface between the bases of the paxillae. The ovaries of these species produce numerous small (ca. 120/«n diameter) eggs which in Plutonaster bifrons appear to show a distinct synchrony of production. Initiation of gametogenesis occurs in June to August of each year with oocyte growthcontinuing until March with a spawn-out in the period March to early June. In specimens where spawningdoesnot occur, there would appear to be internal oocyte degeneration, or after spawning relict oocytesundergo phagocytosis. In males initiation of spermatogenesis may occur in August/September of eachyear but after this synchrony of sperm development is not evident. In Psilaster andromeda gonads are located at the base of the arms and each gonad opens at a single gonopore. A number of small (<300 /«n) oocytes are produced by each gonad. Some of these are phagocytosed and some undergo vitellogenesis and grow to a maximum size of 950 fim before being spawned. Unspent oocytes undergo internal degeneration. In neither females nor males is there any evidence of reproductive synchrony. From these egg sizes, fecundities and gametogenic strategies, we infer indirect planktotrophic development for Plutonaster bifrons, the transfer of a seasonal surface production to deep water providing a food source for developing larvae. The egg size and or close to the sea-bed, as there is no evidence of brooding in this species.
The reproductive cycles of two populations of Coscinasterias muricata from Port Phillip Bay, Victoria, Australia are described in terms of organ indices, oocyte development and progesterone levels. Both Governor's Reef and South Channel Fort populations exhibited clearly defined reproductive cycles with two spawning periods, during summer and during spring. In both populations, the pyloric caecal index and gonadal index showed inverse cycles suggesting nutrient translocation from the pyloric caeca to the gonads for gametogenesis. Physiological changes, such as decreases in pyloric caecal index, and increases in gonadal index and oocyte diameter were observed following the months of increased progesterone concentrations in the female pyloric caeca. These results indicate a role for this steroid in the reproductive cycle. The results from the Governor's Reef population suggest that the influence of progesterone on the reproductive cycle of female C. muricata is regulated by photoperiod. Results also provide evidence of a role for seawater temperature in the reproductive process of this species.
Pawson, David L. (2007): Phylum Echinodermata *. Zootaxa 1668: 749-764, DOI: 10.5281/zenodo.180113
The reproductive biology of the abyssal asteroids Hyphalaster inermis, Styracaster chuni, and S. horridus from the Porcupine Abyssal Plain (PAP), the Madeira Abyssal Plain (MAP), and the northwest African slope (NWA) is described and compared. The most northern location (PAP) is subjected to a strong seasonal input of aggregated phytodetritus to the seabed. The site at MAP does not receive a significant signal of phytodetritus but has been affected recently (ca. 1,000 years ago) by a relatively organic-rich turbidite. The site in the NWA is affected by a strong upwelling regime, which provides the seabed with important inputs of surface-derived organic matter. The gametogenic processes were similar in all three species at the three locations. Oogenesis was asynchronous. The previtellogenic oocytes grow to a size of ~150-200 m before undergoing vitellogenesis. Most of the volume of the ovary was occupied by large vitellogenic oocytes of 300-500 m in diameter. The maximum oocyte size was ~650 m. The males had a continuous supply of spermatozoa densely packed in the lumen of the testes. There were no seasonal variations in gonad index (GI), pyloric caecum index (PCI), and fecundity for any of the species. The GI of H. inermis was similar between locations, indicating a constant allocation of energy to reproduction. The mean GI of S. horridus differed between locations, but there was no clear pattern. Size at maturity and average adult size were larger in the specimens from PAP and NWA than in the specimens from MAP. Fecundity was significantly higher in the specimens from PAP and NWA than in the specimens from MAP. The results are discussed in relation to phylogenetic constraints on gametogenesis and the effects of food quantity and quality on reproductive output.
Pteraster militaris (O. F. Mller, 1776) broods young in an aboral chamber and broadcasts gametes and offspring as well. The reproductive cycle of a population of P. militaris from the northwest Atlantic Ocean was examined over a 23 mo period from September 1985 to July 1987. The species is gonochoric (sex ratio 1:1), with only one incidence of hermaphroditism observed (n=261). Gonad indices were lower in females than in males, possibly an adaptation to the limited space available in the brood chamber. Body component and maturity indices, gonad histology and response to 1-methyladenine indicate that females in the population have a continuous breeding season, with a slight decrease in intensity in the spring. Males have a more pronounced decrease in the intensity of reproduction in the spring. Gonad development in males in synchronous both within and between individuals. Gonad development in females is asynchronous.
A field study was conducted at Wanlitung, southern Taiwan, in 1986–1089, to determine the reproductive cycle, development mode, growth rate and population dynamics of the small seastar Patiriella pseudoexigua (Dartnall), which occurs in highly stressful and disturbed intertidal pools in this area. An inverse relationship between gonad index and pyloric-caccum index was only recorded immediately prior to spawning. A short, well-synchronized seasonal spawning occurs in October. When reared at 25 C, lecithotrophic larvae develop directly, lack a bipinnaria stage, and metamorphose completely on the seventh day after fertilization. The growth curves of field juveniles are linear, those of laboratory-reared juveniles are sigmoid. Juveniles appear in tide pools in spring-early summer of each year. Adults spawn mainly in late fall, enabling spawning to occur in time for the larvae to benefit from the environmentally favorable winter season. Populations in high-tidal pools decrease in later summer, but remain more stable in lowtidal pools and lagoons.
Reproduction of Asterina stellifera was studied in two populations from the Cabo Frio region, southeastern Brazil. One was located in an intertidal seagrass
flat at Japonês Island (1994–1995); the second was on a sublittoral rocky shore at Pontal beaches (1999–2000). Reproductive
cycle was studied at monthly intervals by organ indices and histological examinations of gonads. Although these two populations
were studied in different habitats and at different times, the periodicity of the annual reproductive cycle was very similar
for the two populations. The highest gonad index (GI) values were found in August/September (late winter), followed by a drop
in GI values, indicating spawning. The GI and pyloric caeca index (PCI) tended to have an inverse relationship in both populations,
but it was only statistically significant in the rocky-shore population. Gametogenesis in the two populations was described
and roughly confirmed the reproductive cycles determined by GIs.
The structure, distribution, and population abundance of Oreaster reticulatus (Linnaeus, 1758) in 47,157 ha of shallow-water habitat in the archipelago of Bocas del Toro, Panama, were assessed from May to October 2000. The reproductive cycle of the sea star was studied in Isla Solarte, from February 2000 to February 2001. In total, 4,818 sea stars were recorded with a mean density of 149.7 ind. ha-1, and a population of over 7 million was estimated for the archipelago. O. reticulatus was absent in ca. 50% of the evaluated areas, possibly due to high runoff and sedimentation; highest density was observed in an intermediate-runoff regime (255 ind. ha-1). About 45% of the population was found in substrata dominated by seagrass (Thalassia testudinum) and coarse, calcareous sand, 51% occurred in habitats where coral reef patches were mixed with seagrass, and 4% exclusively on coral reefs. The average size, based on the major radius, was 9.5 cm (3-21 cm), with a population structure composed of ca. 83% juveniles and 17% adults. The average reproductive size, measured as major radius, was 15 cm, and the minimum was 7 cm. Both males and females with a maximum stage (IV) of gonad development were observed throughout the year. The gonad index showed three peaks of maximum reproductive activity, which is not comparable to studies from other localities. The reproductive cycle did not seem to be related to water temperature, which ranged from 27C to 30C, but may respond more closely to changes in local rainfall. This relationship was not statistically significant based on this 1-year study. These data provide a useful baseline for management of local populations in the face of an increasing harvest for the aquarium trade and as souvenirs.
The reproductive and larval biology of the common Antarctic cushion-star Odontaster validus Koehler (Echinodermata: Asteroidea) were studied in a shallow-water population at Signy Island in the maritime Antarctic.
The gonad index peaked in April/May, and injection with 1-methyladenine indicated that competence to spawn peaked in May/June.
Gastrulae were first detected in May, and maximal water-column larval densities were measured in July. Reproduction was therefore
highly seasonal, although not all individuals appeared to spawn each year. The pyloric caeca index increased in summer (typically
November to March, but variable between years) and decreased during winter (June to October), suggesting that feeding activity
was seasonal. All aspects of biology investigated showed significant interannual variability. Comparison with previous studies
in the high Antarctic at McMurdo Sound indicated a similar if more pronounced seasonality at Signy, but the warmer seawater
temperatures in the maritime Antarctic (particularly in late winter/early spring from September onwards) resulted in faster
larval development at Signy.
The northern Pacific asteroid Asterias amurensis (Lütken) has been recently introduced to Tasmania and is now well-established in east and southeast Tasmania. This sea star
is conspicuous throughout the Derwent River estuary and is particularly abundant in the Hobart port area. Reproduction of
two populations of A. amurensis at Sullivans Cove and at Sandy Bay was investigated from August 1993 to October 1994 by gonadal histology and measurement
of the gonad index (GI). An intense period of vitellogenic and spermatogenic growth started in April, with the breeding condition
reached by June. In 1994, peak GI was recorded at Sullivans Cove in July and at Sandy Bay in August. Although these data indicated
that the Sullivans Cove population spawned before the Sandy Bay population, histological examination revealed that major spawning
activity occurred in both populations from July onwards. In the early part of the breeding season, gametogenesis proceeded
in parallel with spawning, with released gametes being replaced by continual gametogenesis. Maintenance of a higher GI during
the early part of the breeding season at Sandy Bay was due to prolonged gametogenic replacement at this site. Spawning continued
to October 1994, resulting in a sharp decline in the GI. The cyclic expansion and regression of the genital haemal sinus coincident
with germinal proliferation and growth, respectively, support the contention that haemal fluid provides nutrients for gametogenesis.
In Tasmania, A. amurensis experiences temperature and photoperiod regimes similar to those experienced by endemic populations of this species in the
north Pacific. Comparison of reproduction of A. amurensis in Japan and Tasmania at similar latitudes shows that gametogenesis of the northern and southern populations is 6 mo out
of phase. This phase shift provides evidence for photoperiodic regulation of gametogenesis in A. amurensis. The similar trend in sea-temperature regimes associated with the stages of gametogenesis in northern and southern populations
suggests that temperature also plays a modulatory role. Based on the periodicity of reproduction and the ontogeny of A. amurensis, the planktotrophic larvae of this species would be expected to be in the plankton for several months from the end of winter
through summer. Considering the highly fecund, dispersive life-history of A. amurensis, the southeast Tasmanian populations have considerable potential to serve as a seed source for establishment of new populations
of this asteroid elsewhere in Tasmania and in mainland Australia.
1.Levels of total fatty acid and carbohydrate were followed in digestive glands and gonads of the starfish, Echinaster, collected at monthly and bimonthly intervals throughout its annual cycle of growth and reproduction.2.Fatty acid almost always occurs in the tissues at over ten times the concentration of carbohydrate and exhibits a more clearly defined systematic variation in the cycle.3.The total content of fatty acid and carbohydrate in the bodies of both sexes increases gradually from summer until a month preceding spawning, the following May. Approximately one-half the accumulated reserves are lost in the final reproductive effort.4.Females tend to have higher fatty acid contents than males because of low levels in the testes. The ovaries begin accumulation of fatty acids in the fall, whereas testes build up only a small amount in the late winter.5.The annual variation in fatty acid content of the digestive glands is due to fluctuations of both the tissue concentration and the size of the organs. Concentration increases in early fall and then declines as the organs enlarge. It is suggested that digestive gland size is only indirectly related to nutritional state and may be under hormonal control.
The histological changes of the gonads of Asterias rubens during the annual reproductive cycle are described. Beyond a juvenile stage, it is possible to define 6 different stages both in males and females. Moreover, in females, the evolution of the diameter of oocytes is followed. We also investigated the reproductive cycle using weight variations of the animals and of some of their internal organs (gonads, pyloric caeca and stomachs). The variations were expressed in two different ways: evolution of the organic indices, and evolution of the regression lines between organ weight and total weight. The results are compared with those of previous authors and the characteristics of the studied population are defined. Pollution is discussed as a possible influence on the small size and the degree of sterility of the coastal starfish population. Finally, from the study of weight variations, it appears that an inverse relation exists between the pyloric caecum weight and gonad weight.
Patterns of reproductive periodicity in the regular echinoid species Diadema mexicanum A. Agassiz and Echinometra vanbrunti A. Agassiz from the Bay of Panama, and Diadema antillarum Phillipi, Echinometra lucunter (Linnaeus) and E. viridis A. Agassiz from the Caribbean coast of the Isthmus of Panama exhibit dissimilarities that reflect the differences of the environments they inhabit. Populations of the two species from the seasonal Bay of Panama display synchronous, well-defined, reproductive cycles. Spawning appears to be timed so that newly metamorphosed sea urchins, rather than larvae, can benefit from the increased food production concomitant with dry season upwelling. On the less seasonal Caribbean shore reproductive periodicity is less defined. Populations of Diadema antillarum and Echinometra lucunter from the vicinity of the Panama Canal show indications of periodicity, while those from a locality 20 km to the east display little tendency for synchrony between individuals. The much rarer E. viridis, on the other hand, maintains well-defined, population-wide cycles in both localities. It is suggested that in a constant environment the intensity of selection for synchrony between individual gametogenic cycles may be inversely proportional to population density.
Most echinoderms display seasonal or other temporal cycles of reproduction that presumably result from the complex interplay of endogenous and exogenous signals. Various environmental, chemical and hormonal factors, acting directly or indirectly, individually or in combination, have been proposed to cue, favour or modulate a suite of reproductive functions from the onset of gametogenesis to gamete release. From as early as the nineteenth century, an astonishing array of studies has been published on topics related to the control of reproduction in echinoderms, ranging from fortuitous behavioural observations to complex experimental demonstrations and molecular analyses. Although the exact pathways involved in the perception of external signals and their transduction into coordinated spawning events remain obscure for most species, significant advances have been made that shed new light on the information gathered over decades of research. By compiling the existing literature (over 1000 references), interpreting the main results, critically assessing the methodologies used and reviewing the emerging hypotheses, we endeavour to draw a clearer picture of the existing knowledge and to provide a framework for future investigation of the mechanisms that underlie reproductive strategies in echinoderms and, by extension, in other marine invertebrates.
The reproductive strategies of an organism play a major role in the dynamics of the population and the biogeography and continuity of the species. Numerous processes are involved in reproduction leading to the production of offspring. Although diverse processes are involved in oogenesis (the production of eggs) and spermatogenesis (the production of sperm), the basic patterns of gametogenesis are similar amongst invertebrates, with the proliferation and differentiation of germ cells leading to the final production of mature gametes. The production of gametes, especially eggs, is energetically expensive, and therefore strongly sensitive to selective pressures. An organism can ingest and assimilate a limited amount of energy from the environment. The different ways by which energy is allocated to growth and reproduction in order to maximize fitness forms the basis of the differing life-history strategies that have developed in marine invertebrates.
Evolution: essays on aspects of evolutionary biology presented to Professor E.S. Goodrich on his seventieth birthday
- J I Baker
Baker J.I. (1938) The evolution of breeding seasons. In De Beer G.R. (ed.)
Evolution: essays on aspects of evolutionary biology presented to
Professor E.S. Goodrich on his seventieth birthday. London: Oxford
University Press, pp. 161 -177.
Supersquirt: dynamics of the Gulf of Tehuantepec
- E D Barton
- M L Argote
- J Brown
- P M Kosro
- M Lavín
- J M R Robles
- L Smith
- A Trasviña
- H S Velez
Barton E.D., Argote M.L., Brown J., Kosro P.M., Lavín M., Robles J.M.
R., Smith L., Trasviña A. and Velez H.S. (1993) Supersquirt:
dynamics of the Gulf of Tehuantepec, Mexico. Oceanography 6,
23-30.