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Bathymetric range, density and reproductive biology of the deep-sea cirrate octopus Opisthoteuthis calypso in the Portuguese continental slope
Abstract
The aim of the present study was to provide the first analysis of depth distribution and reproductive biology in the deep-sea cirrate octopus Opisthoteuthis calypso along the Portuguese continental slope. We used 77 specimens obtained in 7 research cruises between 1996 and 2003. Catch rates and biomass, weights, lengths, sex and maturity stages, and a morphometric description of the beak are detailed. Specimens have been collected from 553 to 960 m depth, south of 39°N, in approximately 1:1 sex-ratio. Females are larger (80:75 mm mantle length) and heavier (622:346 g total body weight) than males and both sexes have been caught in all stages of maturity in equal proportions.
... Several aspects of the biology of this species including distribution, reproduction and diet, have been studied from the samples collected in the east Atlantic (off Namibia, Villanueva, 1992a;Villanueva & Guerra, 1991), off Portugal (Rosa et al., 2009) and the Mediterranean Sartor & Belcari, 2009). Reproduction apparently occurs throughout the year in the Namibian waters (females showed continuous egg production over the entire adult life) and considerable growth occurred in both sexes following the onset of sexual maturity (Villanueva, 1992a). ...
... Individuals found off Namibia are clearly larger (4-5400 g TW, Villanueva, 1992a) than those collected off Portugal (5-522 g TW, Rosa et al., 2009) and the Mediterranean (18-243 g TW, Cuccu et al., 2009;48-162 g TW, Sartor & Belcari, 2009;1-137 g TW, this study) and appear to inhabit the shallower waters. Such size differences among locations of findings could explain the decrease of the slope value in the length-weight relationship from Namibia (b=3.10, ...
... Rosa et al., 2009 and the Mediterranean (b=2.60, this study). Most individuals were picked up at 365-570 m depth off Namibia (Villanueva, 1992a), while at 775-815 m off Portugal (Rosa et al., 2009) and between 685-2208 m in the Mediterranean (871-1420 m, Cuccu et al., 2009;710 m, Sartor & Belcari, 2009;1204-2208m, Villanueva, 1992a685-895 m, this study). Although Villanueva (1992a) observed a tendency for the specimens of both sexes to increase in weight, and consequently reach the sexual maturity stage, with depth, Rosa et al. (2009) did not discover any such tendency. ...
Compared with their shelf-living relatives, the biology and ecology of most pelagic and deep-sea cephalopods are presently relatively little known because of the difficulty in catching them. To compensate for the lack of information regarding these cephalopods, scientists have had to make use of the limited and fragmentary data gathered from different sources, such as sporadic captures, strandings or stomach contents of their predators. In this study, we provide some biological and ecological information on eleven uncommon pelagic and deep-sea cephalopods collected over more than fifteen years of fishery surveys in the western Mediterranean Sea. The cephalopods investigated include two epipelagic octopuses (Ocythoe tuberculata and Tremoctopus violaceus), one deep-sea cirrate octopus (Opisthoteuthis calypso), the sepiolid Stoloteuthis leucoptera and seven teuthoid species inhabiting, preferentially, the mesopelagic and bathypelagic waters (Abraliopsis morisii, Ancistrocheirus lesueurii, Brachioteuthis riisei, Chiroteuthis veranyi, Chtenopteryx sicula, Onychoteuthis banksii and Taonius pavo). Although all of these species are either cosmopolitan or present a wide distribution in other oceans, they are nevertheless relatively rare in catches, and therefore, remain lesser known. The finding of T. pavo represents the first record of this cephalopod in the Mediterranean waters.
... Roeleveld et al. (1992) report finding the species off eastern South Africa. Several aspects of the biology of this species including distribution, reproduction and diet, have been studied from the samples collected in the east Atlantic (off Namibia , Villanueva, 1992a; Villanueva & Guerra, 1991), off Portugal (Rosa et al., 2009) and the Mediterranean (Cuccu et al., 2009; Sartor & Belcari, 2009 ). Reproduction apparently occurs throughout the year in the Namibian waters (females showed continuous egg production over the entire adult life) and considerable growth occurred in both sexes following the onset of sexual maturity (Villanueva, 1992a). ...
... Ovarian oocyte size distributions indicate a continuous-spawning reproductive pattern both in the Nambian (Villanueva, 1992a) and Mediterranean (Cuccu et al., 2009; Sartor & Belcari, 2009) waters. Individuals found off Namibia are clearly larger (4- 5400 g TW, Villanueva, 1992a) than those collected off Portugal (5-522 g TW, Rosa et al., 2009 ) and the Mediterranean (18-243 g TW, Cuccu et al., 2009; 48-162 g TW, Sartor & Belcari, 2009; 1-137 g TW, this study) and appear to inhabit the shallower waters. Such size differences among locations of findings could explain the decrease of the slope value in the length-weight relationship from Namibia (b=3.10, ...
... Mediterranean (18-243 g TW, Cuccu et al., 2009; 48-162 g TW, Sartor & Belcari, 2009; 1-137 g TW, this study) and appear to inhabit the shallower waters. Such size differences among locations of findings could explain the decrease of the slope value in the length-weight relationship from Namibia (b=3.10, Villanueva & Guerra, 1991), Portugal (b=2.74, Rosa et al., 2009) and the Mediterranean (b=2.60, this study). Most individuals were picked up at 365-570 m depth off Namibia (Villanueva, 1992a), while at 775-815 m off Portugal (Rosa et al., 2009) and between 685-2208 m in the Mediterranean (871-1420 m, Cuccu et al., 2009; 710 m, Sartor & Belcari, 2009; 1204 -2208 m, Villanueva, 1992a; 685-895 m, this ...
Compared with their shelf-living relatives, the biology and ecology of most pelagic and deep-sea cephalopods are presently relatively little known because of the difficulty in catching them. To compensate for the lack of information regarding these cephalopods,
scientists have had to make use of the limited and fragmentary data gathered from different sources, such as sporadic captures, strandings or stomach contents of their predators. In this study, we provide some biological and ecological information on eleven uncommon pelagic and deep-sea cephalopods collected over more than fifteen years of fishery surveys in the western Mediterranean Sea. The cephalopods investigated include two epipelagic octopuses (Ocythoe tuberculata and Tremoctopus violaceus),
one deep-sea cirrate octopus (Opisthoteuthis calypso), the sepiolid Stoloteuthis leucoptera and seven teuthoid species inhabiting, preferentially, the mesopelagic and bathypelagic waters (Abraliopsis morisii, Ancistrocheirus lesueurii, Brachioteuthis riisei, Chiroteuthis veranyi, Chtenopteryx sicula, Onychoteuthis banksii and Taonius pavo). Although all of these species are either cosmopolitan or present a wide distribution in other oceans, they are nevertheless relatively rare in catches, and therefore, remain lesser known. The finding of T. pavo represents the first record of this cephalopod in the Mediterranean waters.
... Opisthoteuthis spp. live closely associated with the bathyal bottom (i.e. a benthopelagic existence) (Boyle and Daly 2000;Collins and Villanueva 2006;Rosa et al. 2009b), typically at depths of 300-2200 m (Villanueva et al. 2002). In Portugal, O. calypso is distributed within a restricted area of the continental slope, exclusively over muddy bottoms with (1) the greatest numbers of specimens being found at 775-815 m depth and (2) a mean density value of 0.03 km -2 per 50-or 100-m depth interval within the area of occurrence (Rosa et al. 2009b). ...
... live closely associated with the bathyal bottom (i.e. a benthopelagic existence) (Boyle and Daly 2000;Collins and Villanueva 2006;Rosa et al. 2009b), typically at depths of 300-2200 m (Villanueva et al. 2002). In Portugal, O. calypso is distributed within a restricted area of the continental slope, exclusively over muddy bottoms with (1) the greatest numbers of specimens being found at 775-815 m depth and (2) a mean density value of 0.03 km -2 per 50-or 100-m depth interval within the area of occurrence (Rosa et al. 2009b). ...
... Catches were made by bottom trawling for 60 min with nets equipped with 20-mm mesh codends. From all the specimens collected (see Rosa et al. 2009b), a subset of 28 was measured, weighed, and sexed, with their maturity condition being assessed and classified according to Villanueva (1992) with an added ''maturing'' stage (stage 2), which includes specimens where maturation is well underway but no eggs/spermatophores are visible in the proximal oviduct/seminal vesicle. ...
The present study provides a comprehensive analysis of the biochemical composition (proximate composition, amino acids and fatty acids in gonad, digestive gland and muscle) of the cirrate octopod, Opisthoteuthis calypso, collected off the coast of Portugal. Protein and energy contents of O. calypso were significantly lower (p < 0.05) than those observed for coastal octopods, suggesting that the gelatinous musculature of the cirrate octopus may not be a direct consequence of food limitation, but rather associated with reduced selective pressure for strong swimming ability in the deep sea. Moreover, principal component analyses of fatty acid (FA) data clearly separated coastal octopods from O. calypso. Saturated FA biomarkers (namely 16:0, 17:0, 18:0) and monounsaturated FA 22:1 suggest a higher phytodetrital influence on diet of O. calypso. A clear separation between groups was also observed with amino acid (AA) data. However, essential AA and non-essential AA designations (based on the flow of carbon through biochemical systems) do not necessarily provide an accurate picture of the origins of amino nitrogen in the deep-sea environment. Consequently, the interpretation of the present data is a challenging task but opens a new window of opportunity to unravel new trophic biomarkers in the deep sea.
... Specimens were considered sexually mature based on the presence of spermatophores in the seminal vesicle and/or penis of males and eggs in the oviducts and/or oviducal gland of females (Villanueva et al., 2002). Specimens were considered 'maturing' when gamete maturation was well underway but no eggs/spermatophores were present in the proximal oviducts/seminal vesicle (Rosa et al., 2008). ...
... Interestingly, the depth-ranges reported for the species in the Mediterranean Sea confirm its deeper location in this sea with respect to the Atlantic Namibian and Guinea waters. Even in the Portuguese waters, where the deepest reported bathymetric limits of the catches are 960 m, the upper limit was 553 m (Rosa et al., 2008). ...
... The size of the Sardinian specimens was definitively smaller than that reported for the Atlantic Sea sample (Villanueva et al., 2002;Rosa et al., 2008), both in length and weight; consistently, full maturity was reached at a smaller size in both sexes. Villanueva et al. (2002) stated that considerable growth took place after the onset of sexual maturity; however, spent specimens examined in the present work did not exceed 250 g of total weight, far from the maximum weight of 5400 g and 1600 g reported for males and females, respectively, from Namibian waters. ...
Several aspects of the biology of Opisthoteuthis calypso were studied based on 38 individuals (23 males, 14 females and 1 indeterminate) retrieved from bottom trawls fished at 871 to 1420 m depth in the Sardinian Channel (central western Mediterranean). Data on full maturity of females are presented for the first time for this species. Information on the distribution, size, structure and fecundity for both sexes is provided, and the biological characteristics of the Sardinian samples are compared to those of other Mediterranean and Atlantic samples. Morphological variability and the peculiar structure of the shell and beak are reported and discussed. Molecular DNA sequences were obtained and compared with sequences available for the genus Opisthoteuthis.
... Cirrate biomass density is rarely assessed, and all known estimations are for Opisthoteuthis spp. from temperate areas (Villarroel et al., 2001;Rosa et al., 2009;Pardo-Gandarillas et al., 2021), being much lower than our values from West Greenland which reached 236 kg km -2 . Cirrate abundance density in West Greenland reached nearly 160 ind. ...
... km -2 , which is second highest in the world ocean after Opisthoteuthis massyae (Grimpe, 1920) off Namibia (Villanueva and Guerra 1991, as O. vossi). However, Rosa et al. (2009) included negative trawls in their estimation, while Villaroel et al. (2001), Guerra (1991), andPardo-Gandarillas et al. (2021) included only positive trawls. The high biomass estimation of C. muelleri in the Central Polar Basin, recalculated by Collins and Villanueva (2006) based on underwater photos from Pearcy and Beal (1973), seems subject to a large margin of error because it is based on very limited data where 6 individuals per photo (with over 2900 photos analyzed, 21 of them positive) are the basis of inferring 2000 ind. ...
Stauroteuthis syrtensis and Cirroteuthis muelleri were studied based on representative material collected in Greenland, Iceland, and the Barents Sea and adjacent deep-sea areas (96 stations and 165 individuals for S. syrtensis, and 82 stations and 215 individuals for C. muelleri). The species occur on the border of the Arctic and the northern North Atlantic; S. syrtensis is a southern species and C. muelleri is a northern species, in the area from the Denmark and Davis Straits and associated underwater ridges. These species were demonstrated to be ecological analogues since they: a) occupy the same depths; b) reach the same abundance density; c) reach virtually the same biomass density when corrected for size differences; and d) their food spectra largely coincide. Temperature, not depth, is a principal factor that prevents these species from crossing the border between the Arctic and the northern North Atlantic, with mean habitat temperatures of 3.5 ± 0.06 °C for S. syrtensis and 0.3 ± 0.06 °C for C. muelleri. This study provides unprecedented density estimates for the North Atlantic and Arctic Cirrata: the highest in the world ocean in terms of biomass and second highest in terms of numerical abundance. Food spectra of the studied species consist of Calanoida (including eurybathic Paraeucheta spp. and Calanus spp., and deep-sea Bradyidius similis), Mysidacea and Isopoda (including deep-sea Eurycopinae) (Crustacea), and in C. muelleri also Cumacea, Amphipoda (Crustacea) and Polychaeta (Polynoidae). Additionally, this study: a) provides specific growth and morphometric equations; b) provides equations to estimate mantle length (ML) and body mass (BM) from beak measurements, and BM of fresh individuals (for modelling purposes or predators diet analyses) from BM of fixed individuals; c) reports maximum sizes for C. muelleri (ML 170 mm, total length 400 mm, BM 781.0 g); and d) reports findings of rarely encountered juvenile cirrates.
... Octopus and octopod species are separated into two major groups (sirrate: only deep-sea species; asirrate: mostly benthic) that live from nearshore to the outer continental shelf and slope, including around hydrothermal vents, whereas others live in pelagic habitats [7][8][9]. Deep-sea species can be collected by bottom trawling [10][11][12] and pelagic trawling near continental margins, islands, or seamounts [13][14][15][16][17]. Some deep-sea squid and octopods have been observed using underwater vehicles, which has provided behavioral and life history information [8,[18][19][20][21][22][23]. ...
The circumglobal deep-sea gelatinous giant octopod, Haliphron atlanticus , reaches 4 m in length and uses both benthic and pelagic habitats in the upper 3000 m of the ocean during different life history stages, but it is rarely observed due to the deep-depths where it typically lives. It has been collected in trawls and observed a few times near continental margins or islands and has been identified in the stomach contents of deep-diving predators such as sperm whales and blue sharks or detected as body fragments after predation events. An individual H. atlanticus (~1 m in total length) was video-recorded at 12:21 for about 3 minutes in front of the Shinkai 6500 submersible at 586–599 m (6.5°C, salinity 34.4) along the West Mariana Ridge. It made no escape attempt as the submersible approached and it moved slowly up or down in front of the submersible. It was over the outer seamount-slope (bottom depth ~3208 m) ~50 km west of seamounts (≥1529 m summits), but how it fits into the mesopelagic food web along the ridge is unclear. More information is needed to understand the role of H. atlanticus in oceanic food webs and if it typically lives along seamount ridges.
... Collins et al. 2001) and the same bathymetric range was observed for this species off the Portuguese coast. Greatest occurrences on the southwestern and south-facing coast coincide with reports for other cephalopods in the area (Rosa et al. 2006(Rosa et al. , 2009Czudaj et al. 2012), most probably related to higher productivity and, hence, food availability in near-coastal waters. Survey effort on the northwestern shelf covered mainly shallower (B 250 m) depths, which may influence the overall perception of the abundance of the species in that area. ...
The present study investigated the distribution and general and reproductive biology (size, maturation, fecundity) of the bobtail squid Rondeletiola minor from the Portuguese Atlantic Coast, based on 387 specimens collected between 1997 and 2009, of which 240 were fully analysed. The species was mainly encountered on the southern shelf of the Algarve, in depths of 175�-375 m. Females had mantle lengths (ML) of 10.9-�21.2 mm and were mature from 13.4 mm, while ML in malesranged from 10.4 to 18.9 mm with the smallest mature specimen being 10.4 mm long. The potential fecundity varied from 5 to 460 (mean 228). Mature ova ranged in numbers from 2 to 115 (mean 26), having a diameter of 1.5�3.0 mm (mean 2.0). Oocytes were present in the ovary at different stages of maturity. We also encountered mature specimens with elevated reproductive indices in all sampled months, which is a sign of a multiple spawning strategy with asynchronous ovulation. A peak in reproductive activity is indicated in autumn. R. minor seems to exhibit a comparatively long spawning season, adapted to a life in variable environmental conditions.
... The solid line connects the monthly mean values. proximity to productive coastal waters at the narrower southern shelves (Rosa et al. 2009). This may equally be a main factor influencing the distribution encountered in S. oweniana. ...
the Portuguese Coast is presented based on 594 specimens collected during research cruises between 1997 and 2008. Statolith microstructure was examined in 35 animals. S. oweniana was mainly encountered on the southwestern and southern continental slopes, while it was rare north of 388N. Female mantle length (ML) ranged from 13.9 to 35.7 mm, male ML from 12.5 to 28.0 mm; specimens of both sexes being significantly larger in the southeastern area. Potential fecundity was 18�616 (mean 2349104) oocytes and mean mature oocyte diameter varied 2.3�3.4 mm. The year-round presence of mature animals, asynchronous ovulation, the presence of mature specimens over a range of different sizes and the occurrence of feeding activity throughout spawning are indicative of a continuous spawning strategy in this species. Growth increments were present in all statoliths, being narrow and nearly uniform in width. The total number of growth
increments registered from the specimens sampled varied between 103 and 179; with a similar range in males (n�17) and females (n�18). Putative age estimates suggest an age approximation of 4.5�6 months for mature and spent females and 5� 5.5 months for mature males.
The cirrate octopods are deep-sea, cold-adapted cephalopod molluscs that are found throughout the world's oceans, usually at depths in excess of 300 m, but shallower in cold water at high latitudes. The gelatinous bodies of the cirrates, which deform when preserved, coupled with low capture rates have caused considerable confusion in the systematics of the group. The taxo-nomically relevant morphological features are briefly reviewed and the taxonomy revised. On the basis of morphological and molecular information the cirrates are divided into four families, the Cirroteuthidae (including the genera Cirroteuthis , Cirrothauma and Stauroteuthis), Cirroctopodidae (Cirroctopus), Grimpoteuthidae (Cryptoteuthis , Grimpoteuthis and Luteuthis) and Opisthoteuthidae (Opisthoteuthis). A total of 45 species are recognised. The opisthoteuthids are primarily benthic animals, the grimpoteuthids and cirroctopodids benthopelagic and the cirroteuthids essentially pelagic, but generally close to the sea floor. With the exception of two common, shallow, Opistho-teuthis species, the biology of the cirrates is poorly studied. The data on reproductive biology indicate that spawning is extended, with growth continuing during a reproductive period that probably occupies much of the life cycle, an unusual strategy in cephalopods. Diet studies suggest that benthic cirrates feed on small-sized organisms with low swimming speeds and the main prey are amphipods and polychaetes. Cirrate predators include sharks, teleost fishes, fur seals and sperm whales. Behav-ioural observations, based on underwater photographs, submersible observations and aquarium studies, show a range of postures, modes of locomotion and responses to disturbance that differ between the families. Behavioural observations also help interpret the unusual morphology and physiology of the cirrates, such as the use of cirri, fins, secondary web and bioluminescent emissions.
The distribution of deep-water (150^4850 m) benthic and bentho^ pelagic cephalopods in the north-east Atlantic is described, based on 592 specimens collected from commercial and research trawling. Thirty-six di¡erent species of cephalopod belonging to 14 families were identi¢ed, though problems remain with the taxonomy of some of the octopod genera. At the shallower depths (150^500 m) sepiolids were the most abundant group with ¢ve species identi¢ed. Sepiola atlantica, Sepietta oweniana and Rondeletiola minor were restricted to the shallow depths (5300 m), but Neorossia caroli (400^1535 m) and Rossia macrosoma (205^515 m) extended into deeper water. The squids Todaropsis eblanae and Loligo forbesi were also common in shallow areas (5250 m). Among the incirrate octopods, Eledone cirrhosa was found at depths of 208^490 m. Three putative species of Benthoctopus and two of Bathypolypus were identi¢ed occupying depths of 250^2700 m. Graneledone verrucosa was caught at depths of 1785^2095 m. Cirrate octo-pods dominated the cephalopod catch from the deeper areas, with Opisthoteuthis massyae occurring from 877 to 1398 m, O. grimaldii from 2165 to 2287 m, Stauroteuthis syrtensis from 1425 to 3100 m, Cirroteuthis muel-leri from 700 to 4854 m, Cirrothauma murrayi from 2430 to 4850 m and Grimpoteuthis (¢ve putative species) from 1775 to 4877 m. Abundance estimates of the more frequently caught species were calculated from swept areas of trawls and sledges in the Porcupine Seabight and on the Porcupine Abyssal Plain.
The systematics of the deep-sea cirrate octopod genus Opisthoteuthis Verrill in the Atlantic Ocean is reviewed. Comparisons, based on examination of all extant type material and new, reported and unreported material collected in recent years from the Atlantic, show the presence of five species: Opisthoteuthis agassizii Verrill 1883, O. grimaldii (Joubin, 1903), O. massyae (Grimpe, 1920) and two new species, O. calypso and O. hardyi, which are described. Opisthoteuthis agassizii, distributed only in the western North Atlantic, is redescribed, and a neotype is designated for the presumed lost holotype. Opisthoteuthis grimaldii, distributed in the East Atlantic and possibly also in the western North Atlantic, and O. massyae, distributed in the East Atlantic are also redescribed and junior synonyms listed. Opisthoteuthis calypso, found in the East Atlantic and O. hardyi, known only from a single specimen from the SW Atlantic are described. New morphometric data for O. agassizii, O. massyae and O. grimaldii are given. Illustrations, geographical distributions and a review of the biological information for all five species are provided.
The diet of Opisthoteuthis agassizi and O. vossi in the southeast Atlantic was studied from 171 and 121 individuals respectively. Small epibenthic and supra benthic crustaceans and polychaetes are the most frequent prey items in both species, suggesting that they feed on suprabenthic and epib<:nthic material. Diel analysis of feeding by O. agassizi at 490 m and O. vossi at 836 m depth demonstrated a pattern of continuous feeding. Relationships oftotal body length and beak measurements to total weight were also studied. The ultrastructure of sucker and cirri are described for both species and their relationship with prey detection mechanisms is discussed.
The fecundity and reproductive strategy of three octopus species from the continental slope of the northwest Bering Sea were studied for the first time. Females of Opisthoteuthis californiana produced 1500-2500 eggs, which were released in numerous portions. Their vitellogenesis was specific with continuous asynchrony. Females of Bathypolypus salebrosus released a single portion of 50-160 eggs (60-80% of the initial fecundity pool); the residual oocytes degenerated. For females of Benthoctopus sp., these values were 40-100 eggs and 50-60%, respectively.
The diet of Opisthoteuthis agassizi and O. vossi in the southeast Atlantic was studied from 171 and 121 individuals respectively. Small epibenthic and suprabenthic crustaceans and polychaetes are the most frequent prey items in both species, suggesting that they feed on suprabenthic and epibenthic material. Diel analysis of feeding by O. agassizi at 490 m and O. vossi at 836 m depth demonstrated a pattern of continuous feeding. Relationships of total body length and beak measurements to total weight were also studied. The ultrastructure of sucker and cirri are described for both species and their relationship with prey detection mechanisms is discussed.
The reproductive biology of deepwater cephalopods has received relatively little attention. The cirrate octopus Opisthoteuthis sp. is a regular bycatch in deep benthic trawls from 800 to 1 200 m deep west of Scotland. Specimens were sampled throughout the seasonal cycle. Mature females occurred over a broad size range (600 - <3 000 g wet mass), suggesting considerable growth after maturity, with eggs released singly over a long period of time. There was no significant difference in the gonadosomatic index between spring, autumn and winter samples (p > 0.05), suggesting that there is no seasonal influence on the reproductive status of the population. The ovary of mature females contains eggs ranging in size from <1 mm to a maximum of 12 mm, and each egg is attached in the ovary by a short stalk. Mature females with mature eggs in the distal oviduct, after encapsulation by the single oviducal gland and ready for release, were recorded throughout the annual cycle, further suggesting that timing of spawning is not related to season.
The reproductive strategy of the cirrate octopods Opisthoteuthis agassizii and O. vossi (collected off Namibia from 1988 to 1990) was analyzed. Ovarian oocyte size frequency analysis for both species revealed continuous egg production over the entire adult life span. Mature eggs were stored in the single oviducal gland and distal oviduct, but oviducal gland fullness was not related to body size (p>0.2). All O. agassizii male specimens from 95 to 5400 g total weight were sexually mature, as were all females from 190 to 1650 g, indicating that considerable growth takes place after the onset of sexual maturity. Continuous spawning is defined as a single, extended and continuous period of egg maturation and spawning. This model of reproductive strategy is previously unreported in cephalopods. All O. vossi male specimens from 750 to 3050 g total weight, and females from 800 to 1300 g, were sexually mature. Mature males and females of both species were collected in all seasons of the year. The adaptation of cirrate octopods to non-scasonal deep-sea environments is considered. The sexual maturity characteristics of males were analyzed, and examination of the spermatophore revealed opercular structures previously unreported in cephalopods. For females, the micropyle of the eggs are described and the mineral analysis of the egg shell disclosed that sulphur was the major element present.
Reproductive characteristics of cirromorph octopuses, assigned to the species Opisthoteuthis grimaldii, were sampled as a commercial fishing by-catch on the Hebrides Slope, west of Scotland. A total of 254 specimens (99 female, 155 males), retrieved from bottom trawls fished at 750 to 1500 m depth, were examined. A maximum of 2097 eggs was counted in a single female ovary (mean female body weight 1242.8 g), most of them 500 g (wet wt), and in every female >750 g (max. female weight recorded in the sample was 2959 g), a succession of unattached eggs was present in the proximal oviduct and a single, unattached mature egg occupied the tip of the distal oviduct. These females were assumed to be in spawning condition and the characteristics of egg distribution in the reproductive tract to be consistent with sequential release of individual eggs and continuous spawning throughout the growth period and lifespan of the mature octopus. In pre-spawning females there was a positive relationship between estimated egg numbers and maximum egg size. After the onset of spawning there was no significant further increase in estimated potential fecundity over the body-size range 500 to 3000 g. Follicular sheaths remaining in the ovary after release of eggs into the proximal oviduct were counted and used to estimate the total number of eggs released up to the time of capture. Follicular sheaths first appeared at 500 to 650 g body weight and increased steeply in number to >1000 in females >1500 g. Two individuals were found with ovarian follicular sheaths but with no terminal egg in the distal oviduct; these were assumed to have released their egg just before capture. Summation of the number of follicular sheaths counted plus the number of eggs estimated as remaining attached in the ovisac, provided a revised estimate of total potential fecundity and raised the estimate for any individual to a maximum of 3202 eggs (mean = 1396 eggs).
Although the oceans cover 70% of the Earth's surface and the open ocean is by far the largest ecosystem on the planet, our knowledge regarding diversity patterns of pelagic fauna is very scarce. Here, we examine large-scale latitudinal and depth-related patterns of pelagic cephalopod richness in the Atlantic Ocean in relation to ambient thermal and productive energy availability. Diversity, across 17 biogeochemical regions in the open ocean, does not decline monotonically with latitude, but is positively correlated to the availability of oceanic resources. Mean net primary productivity (NPP), determined from ocean color satellite imagery, explains 37% of the variance in species richness. Outside the poles, the range in NPP explains over 40% of the variability. This suggests that cephalopods are well adapted to the spatial patchiness and seasonality of open-ocean resources. Pelagic richness is also correlated to sea surface temperature, with maximum richness occurring around 15 degrees C and decreasing with both colder and warmer temperatures. Both pelagic and benthos-associated diversities decline sharply from sublittoral and epipelagic regions to the slope and bathypelagic habitats and then steadily to abyssal depths. Thus, higher energy availability at shallow depths seems to promote diversification rates. This strong depth-related trend in diversity also emphasizes the greater influence of the sharp vertical thermal gradient than the smoother and more seasonal horizontal (latitudinal) one on marine diversity.
(in press) Large-scale diversity patterns of cephalopods in the Atlantic open ocean and deep-sea Continuous spawning in the cirrate octopods Opisthoteuthis sp. and O. vossi: features of sexual maturation defining a reproductive strategy in cephalopods
- Rosa R Dierssen
- H M Gonzalez
- L Seibel
Rosa R., Dierssen H.M., Gonzalez L. and Seibel B.A. (in press) Large-scale diversity patterns of cephalopods in the Atlantic open ocean and deep-sea. Ecology. Villanueva R. (1992) Continuous spawning in the cirrate octopods Opisthoteuthis sp. and O. vossi: features of sexual maturation defining a reproductive strategy in cephalopods. Marine Biology 114, 265–275.
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