Effects of temperature and food ration on gonad growth and oogenesis of the green sea urchin, Strongylocentrotus droebachiensis

To assess the effects of both temperature and food ration on gonad growth and oogenesis of the green sea urchin, Strongylocentrotus droebachiensis (O.F. Müller), individuals collected December 1996 (winter experiment) and June 1997 (summer experiment) were maintained for 3 months in one of four experimental treatments: (1) 3 °C and fed ad libitum (high ration), (2) 3 °C and fed one-seventh of the maximum ration (low ration), and (3) 12 °C and fed the high ration; (4) 12 °C and fed the low ration. All individuals were fed an artificial diet and exposed to only 1 h of light every day. At the end of both experiments, mean gonad indices of sea urchins fed the high ration had increased significantly (11–24% and 6–19% in the winter and summer experiments, respectively), while the gonad indices of individuals fed the low ration did not change. At the high ration (both experiments), the increase in gonad index of sea urchins occurred primarily as the result of a significant increase in the mass of nutritive phagocytes, as revealed by histological analyses. Primary oocytes were significantly larger in individuals held at 3 °C than at 12 °C throughout the winter experiment, regardless of food ration; during the summer experiment, primary oocytes were significantly larger in individuals receiving the high ration, regardless of the temperature at which they were held. These results suggest that: (1) food availability is the most important factor regulating energy storage and the relative size of gonads throughout the year, (2) temperature affects the rate of growth and maturation of primary oocytes during the later stages of oogenesis, and (3) once gametogenesis has been initiated, mature ova will be produced, even under conditions of low food availability. Conditions of high food availability in summer and low temperature in winter would thus favor reproductive output in sea urchin populations. Received: 1 March 2000 / Accepted: 4 October 2000     

Effect of temperature on statolith growth of the European squid Loligo vulgaris during early life

Over the past decade, statolith interpretation has resulted in a major advance in our knowledge of squid population-dynamics, but the way in which environmental conditions affect the statolith increment-deposition ratio remains virtually unknown. The object of the present study was to determine the effect of temperature on this process, using tetracycline marks to validate statolith growth in Loligo vulgaris Lamarck, 1798 under rearing conditions equivalent to severe winter (11 °C) and summer (19 °C) temperature regimes. Tetracycline marking was performed every 10 d (at 10, 20, 30, 40, 50 and 60 d of age). The newly hatched squid paralarvae were slightly smaller in summer than those hatched in winter. Survival rates were similar in both cultures, but growth rates (wet mass) of summer squids were double those in winter. At hatching, statoliths were already longer in the summer squids, and growth rates were 2% d⁻¹ as opposed to 0.9% d⁻¹ for winter statoliths. For the dorsal dome area of the statolith, where more increment counts were made, statolith growth was of 3.25 μm d⁻¹ in summer, and daily increment deposition was confirmed in 87% of the statoliths. The slow growth of statoliths at winter temperatures yielded a mean growth of 1.1 μm d⁻¹– insufficient to discern the increments using light microscopy. Subsequent SEM observation enabled only 21% of the winter statoliths to be read; these also indicated a deposition rate of one increment d⁻¹. Since the life span of L. vulgaris is ≃1 yr, squids will experience at least one winter during their life cycle, and this might be visible on the statolith. Received: 28 June 1999 / Accepted: 20 December 1999     

Seasonal variations of ATPase activity and antioxidant defenses in gills of the mud crab <Emphasis Type="Italic">Scylla serrata</Emphasis> (Crustacea,Decapoda)

The mud crab Scylla serrata is an important commercial crustacean being widely distributed along the southeastern coast of China. This crab and particularly its gills are subjected to seasonal fluctuations of environmental factors due to direct exposure to seawater. The investigation of seasonal variations of ATPase and antioxidant defenses in gills could be helpful for the understanding of physiological regulation mechanism of seasonal adaptations. In this study, mud crabs were collected from the subtropical waters near Xiamen island, Southeast China (24°26′46′′N, 118°04′04′′E), in August and November, 2002, and February and May, 2003, respectively, being considered as specimens from summer, autumn, winter and spring, respectively. Only healthy intermoult male crabs without carapace or appendage damage were used, having a carapace width of 7.05 ± 0.52 cm and a wet weight of 130 ± 20 g. The activities of four ATPases and three antioxidation enzymes (superoxide dismutase, catalase, glutathione peroxidase) and the content of malondialdehyde in gills were measured. The results showed that the activities of Na⁺, K⁺-ATPase, Mg²⁺-ATPase, Ca²⁺-ATPase and Ca²⁺, Mg²⁺-ATPase reached maximum levels similarly in summer and decreased in winter. The activities of superoxide dismutase and catalase were higher in summer and lower in winter, with a significant decrease in winter compared to the other seasons (p < 0.01). Glutathione peroxidase activity was higher in summer, and lower in autumn, being significantly higher in summer or winter than in spring or autumn (p < 0.01). Malondialdehyde content was higher in summer and lower in spring with significant differences among the different seasons (p < 0.01). In summary, the obvious seasonal activity variations of four ATPases and antioxidant enzymes and the content of malondialdehyde reflect a seasonal regulation of the physiological metabolising enzyme and the antioxidant capacity to cope with seasonal alterations of environment factors such as fluctuating salinities and temperatures.     

Reproductive biology of a wood-boring isopod, Sphaeroma terebrans, with extended parental care

The isopod Sphaeroma terebrans Bate, 1866 burrows in aerial roots of the red mangrove Rhizophora mangle L. The burrows serve as shelter and as a reproductive habitat, and females are known to host their offspring in their burrows. I examined the reproductive biology of S. terebrans in the Indian River Lagoon, a shallow lagoon stretching for ∼200 km along the Atlantic coast of Florida, USA. Reproductive isopods were found throughout the year, but reproductive activity was highest in the fall and during late spring/early summer. During the latter periods, large numbers of subadults established their own burrows in aerial roots. The average numbers of S. terebrans per root were high during the fall, but decreased during the winter and reached lowest levels at the end of the summer. Females reached maturity at a larger size than males, but also grew to larger sizes than the males. The average size of females varied between 8 and 10 mm, the average size of males between 6.5 and 8.5 mm. The number of embryos female⁻¹ was strongly correlated with female body length. No indication for embryo mortality during development was found. Parental females (i.e. with juveniles in their burrows) hosted on average between 5 and 20 juveniles in their burrows (range 1 to 59). Most juveniles found in female burrows were in the manca stage and 2 to 3 mm in body length. Juveniles did not increase in size while in the maternal burrow, and juveniles of similar sizes could also be found in their own burrows. Males did not participate in extended parental care, since most of them left the females after copulation. Many females that were born in the summer produced one brood in the fall and a second during winter/early spring. Females that were born in the fall produced one brood during spring/early summer, but then probably died. Extended parental care in S. terebrans is short compared to other peracarid crustaceans. It is concluded that this reproductive strategy in S. terebrans serves primarily to shelter small juveniles immediately after they emerge from the female body, when their exoskeleton is still hardening and their physiological capabilities are still developing. Thus, in S. terebrans, extended parental care probably aids to protect small juveniles from adverse physical conditions in their subtropical intertidal habitat. Received: 9 December 1998 / Accepted: 24 June 1999     

Seasonal reproductive biology of the egg-carrying calanoid copepod Pseudodiaptomus marinus in a eutrophic inlet of the Inland Sea of Japan

In situ egg production of the egg-carrying calanoid copepod Pseudodiaptomus marinus was investigated in Fukuyama Harbor, a eutrophic inlet of the Inland Sea of Japan, at 3- to 5-d intervals for a year. This species reproduced throughout the year, and the adults showed a large abundance peak in June/July and a small peak in September/October. Females usually outnumbered males, comprising 61.4% of the annual mean. The composition of ovigerous females varied from 7.9 to 100%, with an annual mean of 55.7%. Adult prosome length was consistently large throughout winter and spring, and decreased with increasing temperature in summer and fall. Egg diameter varied from 98 to 121 μm, and was negatively correlated to temperature. The seasonal variation in clutch size (range: 15.1 to 38.2 eggs) was bicyclical, with peaks in May and December. The egg production rate of breeding females was low in January to March (mean: 2.3 eggs female⁻¹ d⁻¹), while it was constantly high from mid-May to early October (mean: 12.1 eggs female⁻¹ d⁻¹). The specific egg production rate for the breeding females was highly correlated to temperature; it increased linearly from 0.03 d⁻¹ at 9 °C to 0.27 d⁻¹ at 26 °C. Compared to other co-occurring copepods, the reproductive rate of P. marinus was lowest, which is one of the reasons why this species never dominates in this inlet. Received: 11 November 1996 / Accepted: 7 December 1996     

Seasonal variation in the relationship between cellular immune response and badge size in male house sparrows (Passer domesticus)

The immunocompetence handicap hypothesis postulates that secondary sexual traits are honest signals of male quality because steroid hormones (such as corticosteroids and sex steroids), which are supposed to favor the development of secondary sexual traits, may also have immunosuppressive effects. Certain secondary sexual traits are not only used as mate choice signals but also play a role as badges of status. In the house sparrow (Passer domesticus), males have a bib of black feathers which is used both as a signal of social status in male-male interactions and by females when choosing a mate. We investigated the relationships between bib size and cellular immune response in male house sparrows during and outside the reproductive season. Males with large badges were found to have lower levels of immunocompetence, as assessed using a T-cell-mediated immunity assay, during the reproductive season, as predicted by the immunocompetence handicap hypothesis. Conversely, in November, the correlation between badge size and cellular immune response was positive, possibly reflecting the better access to trophic resources of large-badged dominant males in winter flocks. Received: 24 September 1998 / Received in revised form: 2 February 1999 / Accepted: 14 February 1999     

Activity pattern and spatial strategy in Pachygrapsus marmoratus (Decapoda: Grapsidae) from Mediterranean and Atlantic shores

The spatial strategies and activity patterns of two populations of Pachygrapsus marmoratus (Fabricius), from Italy and Portugal, were studied in the field. The Mediterranean site was a non-tidal splash zone about 30 cm wide, while the Atlantic site was a 30 m wide intertidal belt. Almost all P. marmoratus of both populations were active on the emerged rocks, rarely entering the sea. The Mediterranean crabs actively fed on the algal turf throughout the 24 h, while in Portugal active crabs were more numerous at night. In the Italian population, all crabs were packed together, although large males had larger activity areas than females and smaller males. In Portugal, the large males were more concentrated in the sublittoral fringe, while both small males and females were confined to the eulittoral and littoral fringe. The Italian P. marmoratus performed feeding loops within areas smaller than 9 m². Although most Portuguese crabs showed the same spatial strategy, some of them performed feeding migrations to the sublittoral fringe, covering distances of up to 20 m. Environmental factors (e.g. temperature), physical factors (e.g. refuge availability) and biotic factors (e.g. competitors and predators) of the different shores probably determine the behavioural plasticity of␣P.␣marmoratus. Received: 1 February 1998 / Accepted: 13 November 1998     

Growth and reproductive biology of the small penaeid shrimp Trachysalambria curvirostris in Tokyo Bay

We investigated the growth and reproductive biology of the penaeid shrimp Trachysalambria curvirostris in Tokyo Bay, Japan, by monthly bottom-trawl surveys from May 2002 to December 2004. We also examined oogenesis in T. curvirostris by histological observation of the ovary. Females grew faster and attained a larger body size for age than males. The growth rate was high in summer and low in winter and was likely to be associated with seasonal changes in water temperature. The carapace length (CL) at which 50% of females contained vitellogenic oocytes was estimated to be 17.0 mm. The reproductive season extended from May to October. Young-of-the-year appeared in October and could be traced across the months on CL histograms to the following September or October, indicating a 1-year life cycle. This extended reproductive season, together with our observation of asynchronous development of oocytes in the ovary, suggests that multiple spawning by individual females may occur during the reproductive season. Postovulated oocytes were not found among the samples we collected during the daytime, suggesting that final oocyte maturation and spawning occur at night. Cortical crypts in the cytoplasm of the oocyte, considered to be a general feature of oogenesis in penaeid shrimps, were not found in T. curvirostris, even in oocytes undergoing germinal vesicle breakdown. This result implies that the cortical reaction after spawning of T. curvirostris may be different from that of other penaeid shrimps.     

Distribution and abundance of ctenophores and their zooplankton food in the Black Sea. II. Mnemiopsis leidyi

The distribution of Mnemiopsis leidyi Agassiz, 1865 in the Black Sea was determined using plankton samples collected above the anoxic zone (maximum depth 200 m) in the summer, winter, and spring from 1991 to 1995. Distribution was patchy. Average biomasses of 15 to 500 g m⁻² were measured, and abundances varied from 10 to 180 ind m⁻². Biomass and abundance peaked in winter, and there was a secondary peak in the summer. The distribution of M. leidyi was correlated with hydrographic features in the Black Sea with higher concentrations in anticyclonic gyres. The centers of the two main cyclonic gyres generally had a low biomass of M. leidyi. From July 1992 to March 1995, the populations were largely offshore. M. leidyi were confined to the upper part of the mixed layer both day and night. Some individuals displayed a negative taxis to daylight and were concentrated below the thermocline at night. Smaller M. leidyi (1.5 to 2 cm) were present in the winter, and individuals reached maximum size in the summer. Although reproduction was continuous throughout the year, there were two distinct peaks: the larger peak in the summer and the smaller peak in the winter. Microscopic analysis of stomach contents showed that copepods and molluscs form their main diet. Received: 1 November 1997 / Accepted: 30 August 1999     

Variations between winter and summer in the toxicity of copper to a population of the mysid Praunus flexuosus

 Copper toxicity was tested on a coastal population of the mysid Praunus flexuosus (Müller) from Southampton Water (Southern England) under winter and summer conditions. Ten-day toxicity tests were performed on the different life-cycle stages (female, male and juvenile) present in winter (December/February) and summer (August). The individuals were in winter or summer physiological condition and were exposed to seawater to which 0, 5, 25, 75 and 200 μg l⁻¹ copper was added. There were significantly different copper toxicity effects in winter and summer. In winter mortality was ≤ 1% at all levels of copper exposure, while in summer identical exposure levels caused mortality of up to 93%. The 96 h LC₅₀ was 30.8 μg l⁻¹ copper added in the summer. In winter, the low mortality prevented calculation of LC₅₀. There were differences in responses to copper between the life-cycle stages. Juveniles were more sensitive than adults, and were severely affected within 24 h. Females were more affected than males at lower doses and shorter exposure times. Received: 28 April 1999 / Accepted: 22 June 2000     

Reproductive biology of the common shrimp Crangon crangon (Decapoda: Crangonidae) in the central Irish Sea

Aspects of the reproductive biology of the common shrimp Crangon crangon (L.) were studied in Port Erin Bay, Isle of Man, Irish Sea. Size at sexual maturity was determined from the proportions of ovigerous females and of females with maturing ovaries. The size at which 50% of females are mature is estimated (±95% confidence intervals) as 12.5±0.48 mm carapace length. Based on the proportions of ovigerous females and of mature females, the main breeding season was from January to June. Mean ovarian dry weights indicated two broods (winter and summer), with females bearing winter broods (WB) having higher gonad indices than those with summer broods (SB). WB females with non-eyed eggs and with eyed eggs differed in the regression of ovarian dry weight on carapace length, indicating preparation for laying a second brood. In both broods the moult stages of berried females were related to egg stage. Moulting will occur following the release of the brood. During embryonic development, mean egg length and egg volume were larger in all stages, and the mean dry weight of individual eggs of all stages heavier, in WB than in SB; there was no difference in egg number, however. Consequently, reproductive investment, the proportion of female weight devoted to egg production, was 67% higher in WB (0.20±0.04) than in SB (0.12±0.03). There is a significant effect of egg volume on brood weight, but not on egg number. In both broods, egg number was a negatively allometric function of female body size in non-eyed eggs and an isometric function of female body size in eyed eggs. Brood mortality during incubation was higher in SB (17%) than WB (10%). Differences in the reproductive variables and investment between the two broods of C. crangon are discussed in the light of reproductive strategies and life history.Communicated by J.P. Thorpe, Port Erin     

Distribution and abundance of moon jellyfish (Aurelia aurita) and its zooplankton food in the Black Sea

The distribution of moon jellyfish (Aurelia aurita Linnaeus, 1758) in the Black Sea was determined from plankton samples collected above the anoxic zone (maximum depth 200 m) in the summer, winter and spring during 1991–1995. Distribution was patchy. Average biomass ranged from 98 to 380 g m⁻², and abundance varied from 2 to 14 individuals m⁻². Biomass and abundance peaked in late spring and summer. The distribution was correlated with hydrographic features in the Black Sea, with higher concentrations occurring at the peripheries of anticyclonic eddies. Centers of the two main cyclonic gyres generally had a low biomass of A. aurita. From July 1992 to March 1995, the populations were largely concentrated in offshore regions. A. aurita were confined to the upper part of the mixed layer. Smaller A. aurita (≤1 cm) were present in early spring (March), and individuals reached maximum size in the summer. Release of the epyhrae occurred in spring on the northwestern shelf of the sea when the seawater temperature was 11–12 °C. Microscopic analysis of stomach contents showed that copepods and mollusks form their main diet. Received: 3 September 2000 / Accepted: 29 September 2000     

Waterborne cues from crabs induce thicker skeletons, smaller gonads and size-specific changes in growth rate in sea urchins

Indirect predator-induced effects on growth, morphology and reproduction have been extensively studied in marine invertebrates but usually without consideration of size-specific effects and not at all in post-metamorphic echinoids. Urchins are an unusually good system, in which, to study size effects because individuals of various ages within one species span four orders of magnitude in weight while retaining a nearly isometric morphology. We tracked growth of urchins, Strongylocentrotus droebachiensis (0.013–161.385 g), in the presence or absence of waterborne cues from predatory Jonah crabs, Cancer borealis. We ran experiments at ambient temperatures, once for 4 weeks during summer and again, with a second set of urchins, for 22 weeks over winter. We used a scaled, cube-root transformation of weight for measuring size more precisely and for equalizing variance across sizes. Growth rate of the smallest urchins (summer: <17 mm diameter; winter: <7 mm diameter) decreased by 40–42% in response to crab cues. In contrast, growth rate of larger urchins was unaffected in the summer and increased in response to crab scent by 7% in the winter. At the end of the 22-week experiment, additional gonadal and skeletal variables were measured. Cue-exposed urchins developed heavier, thicker skeletons and smaller gonads, but no differences in spine length or jaw size. The differences depended on urchin size, suggesting that there are size-specific shifts in gonadal and somatic investment in urchins.     

Seasonal variation of membrane fluidity of the naturally acclimatized Baltic Sea amphipods Gammarus spp. and Monoporeia affinis

The membrane fluidity of the Baltic Sea crustaceans Gammarus spp. and Monoporeia affinis was studied in different seasons. Gammarus spp. were collected at a location with stable salinity and with temperature fluctuations from about 0 to 20 °C, and M. affinis at a deep location with stable salinity and a constant low temperature of about 1.5 to 4.5 °C. The membrane fluidity was measured from preparations enriched with plasma and mitochondrial membranes employing a fluorescence polarization technique using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a probe. The measurements were carried out without any preceding acclimation of the animals. In Gammarus spp., the membrane fluidity increased in the order: summer animals < autumn animals < spring animals. The differences between seasons were significant, with pronounced homeoviscous adaptation, and correlated well with the water temperature. It is suggested that in Gammarus spp., temperature is the determining factor for membrane fluidity. In M. affinis, the membranes of summer animals were the most fluid, and there was a significant difference only between summer and spring animals. In M. affinis the difference was not connected to the water temperature and no homeoviscous adaptation was noticed. The deep-water M. affinis experience a long period of fresh food deficiency, which probably affects the membrane fluidity. Although there are seasonal differences in fluidities between Gammarus spp. and M. affinis, it is interesting to note that all data obtained from M. affinis settled between the polarization lines of spring and summer Gammarus spp., regardless of the prevailing temperatures. Received: 30 June 1999 / Accepted: 7 June 2000     

Distribution and abundance of ctenophores, and their zooplankton food in the Black Sea. I. Pleurobrachia pileus

The distribution of Pleurobrachia pileus Müller, 1776 in the Black Sea was determined using plankton samples collected above the anoxic zone (maximum of 200 m) in the winter, spring, and summer of 1991 to 1995. The summer samples were collected in 1991 to 1993 (for a previous) and are included in this paper for comparative purposes. High concentrations of P. pileus were found at the northern edges of anticyclonic eddies along the southern coastal regions. The biomass and abundance of P. pileus increased from winter through spring to a peak in summer. The highest mean wet weight during a sampling period was 250 g m⁻², while the maximum wet weight was 1429 g m⁻². P. pileus was mostly found in a layer extending from the lower parts of the thermocline down to the anoxic zone, where the temperature was <8 °C. The vertical distribution of P. pileus biomass had two clear maxima at night: an upper maximum at 20 to 40 m was less pronounced than the lower maximum at 90 to 120 m depth. Mean body length of P. pileus did not exceed 12 mm. Smaller individuals (9 to 10 mm length) occurred in winter. P. pileus had two length classes in early spring (March 1995) and late summer (August 1993), indicating the presence of both newly hatched and larger individuals. Overall, the stomach contents of P. pileus consisted mainly of Copepoda (90%), Cladocera (1%), Mollusca (1%), fish eggs and larvae (1%), and other taxa (7%). The preferred food of P. pileus (frequency of occurrence) was: Calanus euxinus (39%), Pseudocalanus elongatus (30%), Acartia clausi (28%), Oithona similis (2%), and Paracalanus parvus (1%). The endoparasite Hysterothylacium aduncum was commonly found in P. pileus. Abundances of Mnemiopsis leidyi and P. pileus were either negatively correlated (r = −0.5 to −0.7) or positively correlated at a low significance level (r = 0.25 to 0.3) with abundance of A. clausi in different months of the year. Aurelia aurita abundance was correlated mainly with the abundance of C. euxinus from June 1991 to March/April 1995. Over the same period the abundance of P. pileus was significantly correlated with the abundance of P. elongatus, an important prey species. Received: 1 November 1997 / Accepted: 30 August 1999     

Resource acquisition in two intertidal fucoid seaweeds, Fucus serratus and Himanthalia elongata : seasonal variation and effects of reproductive development

Seasonal variations and the effect of reproductive development on resource acquisition by two intertidal fucoid species, the iteroparous Fucus serratus L. and the semelparous Himanthalia elongata (L.) S. F. Gray were examined. The oxygen-exchange characteristics of vegetative apical tissue of both non-fertile and fertile plants and receptacle tissue were compared at monthly intervals throughout reproductive development. Respiratory rates in non-fertile F. serratus varied seasonally between 1.5 and 8.0 μmol g⁻¹ fresh wt h⁻¹; in fertile plants the receptacle had a significantly lower respiratory rate than the vegetative tissue. The respiratory rate of the vegetative button of fertile H. elongata displayed less seasonal variation and was lower than that of the receptacle, which varied from a maximum of 9.5 μmol g⁻¹ fresh wt h⁻¹ at receptacle initiation in October to a minimum of 2.0 μmol g⁻¹ fresh wt h⁻¹ in February. The maximum photosynthetic rate (P _max) of non-fertile plants of both species did not vary in a distinct seasonal manner (∼60 μmol g⁻¹ fresh wt h⁻¹ for F. serratus and ∼12 μmol g⁻¹ fresh wt h⁻¹ for H. elongata). In fertile plants, the P _max of the receptacle tissue was (∼50% lower in F. serratus, and at its peak three times higher in H. elongata, than that of vegetative tissue. The stable carbon-isotope ratio (δ¹³C) did not differ between different tissue types in F. serratus, but values did vary seasonally, being less negative in the summer than in the winter (−13.5‰ compared to −18‰). The receptacle tissue of H. elongata also displayed a distinct seasonal variation in δ¹³C values (−12‰ in summer, −16‰ in winter), whilst the δ¹³C of the vegetative button did not vary seasonally. The rate of uptake of inorganic nitrogen by the vegetative thallus was lower in H. elongata than in F. serratus. The receptacle tissue of F. serratus had lower uptake rates than the vegetative tissue, whilst the uptake rate by H. elongata receptacle tissue was higher than that of the vegetative button. Received: 14 March 1997 / Accepted: 22 April 1997     

Seasonal variations in hepatopancreas fatty acid profiles of two colour forms of shore crabs, Carcinus maenas

 The relationship between intermoult duration (coloration), sex, size and seasonal variations in fatty acid (FA) profiles was studied in a population of shore crabs, Carcinus maenas, inhabiting the Isefjord, Denmark. For male shore crabs, the total hepatopancreas FA content was high in July and December (12.7 to 16.0 mg g⁻¹ dry weight, dw) but lower in May and September (7.3 to 10.0 mg g⁻¹). This indicates that male shore crabs are in relatively good condition before winter, when the crabs migrate off shore, but in relatively poor condition when they return to shallow waters during spring. The hepatopancreas FA content also decreased over the mating season. After the mating season the hepatopancreas FA content of males had decreased to approximately 60% of that prior to the mating season. Female shore crabs had significantly higher hepatopancreas FA levels than males in May (11.7 mg g⁻¹ dw), September (12.6 mg g⁻¹ dw) and December (17.9 mg g⁻¹ dw) but lower levels in July (9.5 mg g⁻¹ dw). This indicates that the spawning season is the most energy-demanding part of the female reproductive cycle. For all seasons, the hepatopancreas FA content of green shore crabs was significantly higher than that of red shore crabs. For both colour forms, the amount of polyunsaturated fatty acids (PUFAs) was significantly higher than that of saturated fatty acids (SAFAs) and monounsaturated fatty acids (MUFAs), with the relative proportion of PUFAs increasing when the total hepatopancreas FA content decreased. For both genders and colour forms, the most dominating SAFA was palmitic acid (16:0). Palmitoleic acid (16:1ω7), vaccenic acid (18:1ω7) and oleic acid (18:1ω9) were the three MUFAs found in highest concentrations. The most dominating PUFA was eicosapentaenoic acid (EPA, 20:5ω3). Docosahexaenoic acid (DHA, 22:6ω3) and arachidonic acid (AA, 20:4ω6) were also abundant in all samples. The results demonstrated that season, sex, size and intermoult duration all influence the amount of FAs present in the hepatopancreas of shore crabs. Received: 23 September 1999 / Accepted: 29 April 2000     

Reproductive dynamics of endeavour prawns, Metapenaeus endeavouri and M. ensis, in Albatross Bay, Gulf of Carpentaria, Australia

 The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort, and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths <50 m and was concentrated particularly in inshore waters (<20 m) in spring. In autumn, the spawning output was mainly from the autumn-spawning cohort, which comprised but a small number of individuals. In winter, the major spawning group again consisted of the large females from the spring-spawning cohort, and spawning increased in the oceanic waters (>50 m). These results suggest that mature female M. endeavouri and M. ensis move offshore (>40 m) by May and July, respectively, and return to shallow waters (<35 m) in July and November, respectively. The monthly reproduction patterns of both species in the “effective spawning” area showed that the major spawning season for M. endeavouri is August to October and that for M. ensis is September to December. Received: 19 February 1999 / Accepted: 18 June 2000     

Reproductive biology and ecology of a deep-demersal fish, alfonsino Beryx splendens, over the seamounts off New Caledonia

The reproductive biology of the alfonsino Beryx splendens was studied by histological examinations, gonadosomatic index and macroscopic scales of maturation of a large sample of gonads. Alfonsino is a gonochoric species. The size-frequency distribution of the sex ratio was bimodal and considered to be due to size dimorphism. In New Caledonia, the breeding period of this species occurs during the southern summer, with a peak in December to January. The spawning stage is attained at a minimum fork length of 28 cm for females and 33 cm for males. The size at which 50% of the population attain sexual maturity (FL₅₀) is 33.2 cm for females and 34.5 cm for males. Maximum potential fecundity is estimated to lie between 270 000 to 675 000 eggs for fish between 34 and 40 cm in fork length. It was possible to differentiate vegetative zones, in which juvenile alfonsino grow until they reach maturity, from reproductive zones (fishing grounds) which are inhabited by mature individuals. The larvae and juveniles could be carried from the reproductive zone to the vegetative zone by currents in an oceanic eddy system. Received: 26 April 1996 / Accepted: 20 September 1996     

Some effects of temperature on the growth and metabolic rate of juvenile blue crabs,Callinectes sapidus,in the laboratory

Juvenile blue crabs, Callinectes sapidus Rathbun, were grown in the laboratory at different temperatures, and metabolic-rate determinations were made. Growth is shown to be dependent upon temperature. Crabs kept at high temperatures (34° and 27°C) grow faster than those kept at lower temperatures (13°, 15°, and 20°C). Increase in size per molt is less at higher temperatures than at lower ones. Mortality is directly proportional to temperature between 13° and 34°C and is very high during ecdysis at elevated temperatures. Metabolic rate increases with temperature, but various degrees of acclimation are seen after 4 weeks exposure. No acclimation of general activity to temperature was found. The findings are applied theoretically to crabs living in the region of heated discharge canals of electrical generators: the motile blue crab could extend its growing season without decreasing size at maturity by active selection of thermal surroundings.In part based on a thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science at the University of Florida, USA.