The annual reproductive cycles of Uca annulipes,Portunus pelagicus and Metapenaeus affinis (Decapoda: Crustacea) from the South-west coast of India

Employing the gonad index method, the reproductive cycles of three decapod crustaceans, Uca annulipes (Latreille), Portunus pelagicus (Linnaeus) and Metapenaeus affinis (Milne-Edwards) have been studied. In these crustaceans breeding is not continuous all the year round, but extends over several months of the year with distinct peak periods of gonadal activity. The male and female reproductive cycles are not concurrent. The peak of the reproductive cycle of males occurs slightly earlier in the breeding season than that of females. These studies indicate the possibility of production of successive broods of eggs during the same breeding season. In these species, the low saline conditions of the monsoon period are unfavourable for breeding. The medium and high saline conditions during the post-monsoon and pre-monsoon months, respectively, with plenty of planktonic food for the larvae, seem to be the favourable periods for breeding activity.     

Evidence for acclimation to hydrostatic pressure in Uca pugilator (Crustacea: Decapoda: Ocypodidae)

Groups of male Uca pugilator (Bosc) (Crustacea, Decapoda, Ocypodidae), acclimated to sublethal pressure (34 atm) subaqueously for 5 and 10 days, were observed subsequently at pressures up to 272 atm. Behavioral indicators of pressure resistance (“first response” and tetany) were employed to measure degrees of pressure acclimation in comparison with simultaneously and non-simultaneously conducted control experiments. No firm conclusions can be made on the basis of “first response” results, but the pressures required to induce tetany were significantly higher (P≤0.02, one-tailed comparison) in acclimated groups than in non-acclimated groups. These data and earlier studies by other investigators support the assertion that some shallow marine species are capable of at least limited short-term pressure acclimation.     

Seasonal changes in biochemical composition of body walls,gonads and pyloric caeca in two populations ofSclerasterias mollis (Echinodermata: Asteroidea) during the annual reproductive cycle

Seasonal changes in biochemical composition of tissues are compared in a shallow inshore and deeper offshore population of the seastarSclerasterias mollis (Hutton, 1872) on the Otago shelf, New Zealand, from 1985 to 1986. The biochemical composition of the body wall, gonads and pyloric caeca of the two populations did not differ greatly, even though reproductive output and nutrient storage of reserves were consistently higher in the offshore population. The biochemical composition of the ovaries and testes differed. High levels of carbohydrate and lipid were maintained in the ovaries from the commencement of vitellogenesis until spawning occurred. The testes had higher ash levels during spermatogenesis. During the annual reproductive cycle, an inverse relationship in the carbohydrate levels between the ovary and the pyloric caeca suggests nutrient transfer from the pyloric caeca to the gonads during gametogenesis. Annual changes in biochemical composition indicate that the body wall is also used for nutrient storage.     

R-cells and the digestive cycle in Penaeus semisulcatus (Crustacea: Decapoda)

Shrimp, Penaeus semisulcatus, were collected from Kuwaiti waters in 1980, and the R-cells in the hepatopancreas were observed during the digestive cycle. During the first 12 h they absorb soluble material from the lumen of the gland and, subsequently, they take-up soluble and particulate material from the haemolymph. Within the cytoplasm, apical and basal systems of smooth endoplasmic reticulum are concerned with these processes. Pinocytosis only occurs at the basal cell membrane. The absorbed material is stored as lipid and glycogen, and copper, sulphur and other elements are accumulated in a large dense vacuole. These activities are integrated with those of the other cell types to effect the assimilation of food in the hepatopancreas. A scheme is proposed which accounts for the main processes of digestion. The hepatopancreas governs the duration of the digestive cycle, which takes at least 24 h. Observations on the nature of intracellular storage and waste products could be used to assess the dietary requirements of artificially reared shrimp.     

Functional cytology of the hepatopancreas of Penaeus semisulcatus (Crustacea: Decapoda) during the moult cycle

In the shrimp Penaeus semisulcatus, the digestive gland functions as the main site for the digestion, absorption and storage of nutrients and metals during the feeding stages of intermoult and for the mobilization of reserves during the non-feeding stages of pre-and post-moult. These different activities are reflected directly in the cytology of the gland. All the epithelial cells show marked fluctuations in frequency and changes in structure, form and function which occur in phase with the moult cycle. The shrimp were collected offshore from Kuwait in 1980.     

Ontogenetic variation in metabolism, biochemical composition and energy content during the early life stages of Farfantepenaeus paulensis (Crustacea: Decapoda: Penaeidae)

Dry weight (DW), oxygen consumption, ammonia-N excretion, proximate biochemical composition (total protein, carbohydrate, lipid, water and ash), and energy content (estimated from biochemical composition and by wet combustion) were determined in early developmental stages of cultured Farfantepenaeus paulensis. Pooled samples from embryonic, larval and postlarval stages (at 26 ± 1 °C and 34 ± 1‰) were used for measurements. The study focused on physiological and biochemical processes during transitional periods of ontogeny, such as hatching, lecithotrophic and planktotrophic stages, metamorphosis, and the attainment of a benthic existence in postlarva. DW showed higher increment between protozoea I (PZ I) and mysis I (M I) than in the next mysid and postlarval stages. Individual rates of oxygen consumption and ammonia-N excretion increased, while weight-specific rates presented significant reduction throughout development. Higher weight-specific oxygen consumption was registered in nauplius III (N III) and PZ I, following a decrease in subsequent stages. Postlarval stages PL V–VI and PL X–XII exhibited the lowest values among the stages studied. Weight-specific excretion was high in N III and protozoeal stages, with maximum values in PZ II, while the following stages were marked by lower rates. O:N ratios indicated higher protein catabolism in the stages between egg and M I and a shift to more lipid utilization close to metamorphosis. Water content was higher in the protozoeal stages and decreased afterwards. Higher percentages of protein, lipid and carbohydrate (%DW) were observed in egg and nauplius stages. Protein and lipid decreased from the egg through the naupliar and protozoeal stages, rising again in mysis stages. Lipid content (%DW) decreased in PL V–VI and PL X–XII. Lipid:protein ratios showed an increase of the importance of lipid between PZ III and M II. Carbohydrates represented a minor fraction of body composition, and ash percentages increased from egg to a maximum in PZ II, decreasing in subsequent stages. Energy content determined by wet combustion or calculated by energy equivalents presented the same trend throughout development, varying similarly to protein. Protein was the main energy contributor to body energy in all stages, while the importance of lipid was higher in egg and early naupliar stages. Trends observed in metabolic rates and body composition may be associated to morphological and behavioral changes during the early stages of penaeid development, such as the transition from herbivory to omnivory, and the adoption of a benthic existence. Different ontogenetic energy strategies contribute to succeed through such diverse type of development. Received: 4 July 2000 / Accepted: 6 December 2000     

Reproductive cycle of the brooding echinoid Abatus cordatus (Echinodermata) in Kerguelen (Antarctic Ocean): changes in the organ indices,biochemical composition and caloric content of the gonads

Variations in organ indices, organic levels, organic and caloric contents of the gonads of the brooding echinoid Abatus cordatus (Verrill), collected in the Morbihan Gulf (49°30′S; 70°E) were studied over a 1 yr period (March 1978 to January 1979). In both sexes, a clear annual cycle was discernable for organ indices, and for organic and caloric contents. In contrast, the protein levels in the gonads varied moderately, while the levels of lipid and carbohydrate remained almost constant. This peculiarity sets A. cordatus apart from nearly all other echinoids characterized by an annual reproductive cycle. The male and female gonad indices change synchronously. The gonad indices double during maturation, reflecting variations in the germinal tissue. In both sexes, the maximal gonad index (at the end of March) coincides with the onset of the spawning season. The average male gonad index is 50% higher than that of the female. This difference is related to the restriction of coelomic space in the female due to development of the brood pouches. At maturity, the lipid and carbohydrate levels in the ovary are 2.8 and 2.1 times greater, respectively, than the levels in the testis, the latter having a 25% higher protein level. This disparity in organic levels reflects mainly the differences in germinal tissue composition. The female reproductive effort is higher than that of the male. The spawn energy output of a standard individual is 200 cal for a male and 228 cal for a female. The unusually lower gonad index of the female is compensated for by higher lipid and carbohydrate levels, giving the ovary a 40% higher calorific value.     

Physiological and biochemical changes during lecithotrophic larval development and early juvenile growth in the northern stone crab,Lithodes maja (Decapoda: Anomura)

Larvae of the northern stone crab, Lithodes maja L., were reared in the laboratory from hatching to the second crab stage. complete larval development (at constant 9°C) lasted about 7 wk, invariably consisting of three pelagic zoeal stages and a semibenthic Megalopa; only two zoeal stages have been described in the literature. All larval stages are lecithotrophic. First feeding was consistently observed only after metamorphosis, in the first juvenile crab stage. In short intervals (every 1 to 5 d), developmental changes in biomass, B (expressed as: dry weight, W; carbon, C; nitrogen, N; hydrogen, H) and oxygen consumption (respiration, R) were measured in larvae and early juveniles; additionally, protein and carbohydrates were measured, but only in the zoeal stages and early Megalopa. Unusually high C contents (varying between 56 and 61% of W in eggs and freshly hatched Zoea I larvae from 12 different females) and high C:N weight ratios (8 to 11) indicate enhanced initial lipid stores, which are utilized as the major metabolic substrate during both embryonic and lecithotrophic larval development. Predominant degradation of lipids is shown indirectly; the C:N ratio decreased significantly, from 10 (at hatching) to 6 (at metamorphosis), while larval protein decreased only little, from ca. 55% of W (at hatching) to 48% (in the Megalopa). From hatching to metamorphosis, about 27% of the initially present W, 48% of C, 18% of N, and 52% of H were lost. This decrease in larval biomass can be described as an exponential function of development time. The major part of these losses were associated with metabolic energy requirements, while exuvial losses were comparably small. In each of the zoeal stages, only about 1 to 2% of late premoult (LPM) B was shed with the exuvia. The Megalopa, which produces a much thicker, calcified exoskeleton, lost 20% of LPM W, but only 5 to 8% of organic constituents (C, N, H). Much higher exuvial losses were measured in the Crab I stage (51% in W, 21% in C, 5% in N, and 7% in H). Maximum respiration was found in the actively swimming zoeal stages, a minimum in the predominantly benthic, mostly inactive Megalopa. The Crab I stage exhibits also a sluggish behaviour and low R, in spite of beginning food uptake and growth. Immediately after metamorphosis, the juvenile crab gained rapidly in W, in particular in its C fraction. A transitorily steep increase in the C:N ratio indicates a replenishment of partially depleted lipid stores, but also a rapid initial increase of inorganic C in the heavily calcified exoskeleton. Instantaneous rates of growth, assimilation, and net growth efficiency (K ₂) were high during the initial (postmoult) phase in the first juvenile crab stage (C-specific growth rate: 6% d^-1; K ₂:70%), but decreased towards zero values during laterstages of the moulting cycle; metabolism remained practically constant during the Crab I stage. Entirely lecithotrophic larval development from hatching to metamorphosis in L. maja is considered an adaptation to seasonally short and limited planktonic food production in subarctic regions of the northern Atlantic.     

Effects of cadmium on Pontoporeia affinis (Crustacea: Amphipoda) in laboratory soft-bottom microcosms

Laboratory soft bottom microcosms, containing sediment with natural populations of meio-and microfauna and the amphipod Pontoporeia affinis Lindström, were used to investigate chronic effects of cadmium on a typical Baltic Sea benthic community. Temperature, salinity, organic content of the sediment and the life cycles of the amphipods in laboratory control microcosms were in good agreement with conditions in the Baltic Sea. In Experiment 1, P. affinis was exposed to four assayed cadmium concentrations, 0 (control), 6.3, 41 and 127 g Cd·1^-1, for 265 d. At the lowest cadmium concentration (6.3 g Cd·1^-1), the sediment contained about 700 times, and P. affinis about 1 700 times, the water concentration at the end of the experiments. In microcosms without P. affinis, the sediments accumulated less cadmium. Effects on P. affinis embryogenesis were detected after 105 d of exposure in all tested cadmium concentrations. Mortality of juveniles was significantly increased after 265 d of exposure in mean assayed concentrations of 41 and 127 g Cd·1^-1. In Experiment 2, P. affinis was exposed to cadmium in assayed concentrations, 0, 6.5 and 46 g Cd·1^-1 for 460 d. At the lowest water concentration (6.5 g Cd·1^-1), the prolonged exposure did not increase the sediment concentration, which indicates a steady state, while concentrations in P. affinis reached about 3 500 times the lowest water concentration after 460 d. Juvenile P. affinis matured sexually and reproduced normally in all microcosms, but their offspring died in all microcosms with added Cd. This occurred at water concentrations not uncommon in polluted marine areas. The effects are serious in comparison to those found in conventional short-term laboratory experiments with the same concentrations and demonstrate the importance of long-term experiments in ecotoxicology.     

Action of eyestalks on the ovary in Rhithropanopeus harrisii and Crangon crangon (Crustacea: Decapoda)

The annual cycle of ovarian activity and eyestalk effects on the ovary in different phases of its activity were examined in the crab Rhithropanopeus harrisii Gould ssp. tridentatus Maitland, and the sand shrimp Crangon crangon L. In both species, the annual ovarian cycle consists of two phases of vitellogenesis and the resting phase. In R. harrisii, the eyestalks exert an inhibitory effect on vitellogenesis during the phase of vitellogenesis outside the breeding season, and are necessary for the process of oviposition during the breeding season. In C. crangon, ovary-inhibiting hormone is present in the eyestalks outside the breeding season, and has not been detected during this season. The resting phase of the ovary after the breeding season is caused by the ovary-inhibitiing hormone. Females of C. crangon are a suitable material for testing ovary-inhibiting hormone activity, while female R. harrisii are not.     

Metals in Cancer irroratus (Crustacea: Decapoda): Concentrations,concentration factors,discrimination factors,correlations

Nine metals were analysed in whole specimens of the decapod crustancean Cancer irroratus, and three in the exoskeleton of Carcinus maenas. In terms of concentrations (expressed as parts per millions) and concentration factors, 2 groups of metals could be distinguished in Cancer irroratus: Zn, Cu, Fe and Mn in one group, Ca, Mg, Sr, Na and K in the other group. Na excepted, all the metals had concentration factors significantly higher (P<0.01) than 1. The concentration factor of Na was significantly lower (P<0.01) than 1, demonstrating the existence in C. irroratus of a barrier to the movement of Na into the crustacean from its environment. Studies of coefficients of discrimination (D), in C. irroratus, for metals considered in pairs, showed, in each case that D was significantly different (Plt;0.01) from 1. Only the discrimination factor between, Zn and Mn was less significantly different (0.05lt;Plt;0.1) from 1. Correlations were made between the concentrations of metals and other parameters: water content, size, and ash content. Significant correlations were found, especially in the cases of the pairs Ca?Sr, Na?K, Cu?Zn, and Mn-animal size.     

Larval settlement and metamorphosis in the sand crab Emerita talpoida (Crustacea: Decapoda: Anomura)

The effects of various potential cues on the survival and time to metamorphosis of larvae of the sand crab Emerita talpoida (Say) were examined. Zoeal duration, which ranged from 25 to 43 d, was not correlated with subsequent megalopal survival but had a weak, negative correlation with the duration of the megalopal stage. Neither food, sand nor water from containers with adults directly affected megalopal survival or duration. In a second experiment, the presence of sand both increased the probability of survival and shortened the duration of late zoeal stages. This is the first experimental evidence for delayed zoeal metamorphosis in a decapod. Settlement of E. talpoida appears to occur primarily during the zoeal phase, not at the megalopal stage.     

Changes in the neurosecretory cells of the brain and thoracic ganglion of male crab,Uca (celuca) lactea annulipes with respect to seasons

The change in the neurosecretory cells with males with respect to seasons was investigated. The brain is provided with three types of neurosecretory cells namely A, B and C and thoracic ganglion with four types of neurosecretory cells A, B, C and D. They vary in number and neurosecretory activity according to seasons which may be responsible for the increase in the size and development of the reproductive and associated structures.     

Changes in lipid class and fatty acid contents in the ovary and midgut gland of the female fiddler crab Uca tangeri (Decapoda,Ocypodiadae) during maturation

Changes in biochemical composition, lipid class and fatty acid contents were studied in the ovaries and midgut glands of the fiddler crabs Uca tangeri Eydoux during maturation. Wild females were caught during spring and early summer of 1992 in the Bay of Cádiz (southwest Spain), near the mouth of the San Pedro river. Protein and total lipid contents in the ovaries increased significantly from Stages III to IV, at the expense of total carbohydrate, which showed a large decrease during the same period. In the midgut gland, the protein content did not present any significant variation, whereas total lipids and total carbohydrates presented opposite up and down trends during maturation. In the ovary, total polar lipids increased significantly during the final phase of maturation (Stages III to IV), mainly due to the significant contribution of the phosphatidylcholine and phosphatidylethanolamine fractions. In contrast, total neutral lipids showed an upward trend throughout the whole maturation period, mainly due to significant increases of the triacylglycerol fraction. In the midgut gland, total polar lipids (mainly phosphatidylcholine) and total neutral lipids (mainly triacylglycerol) presented significant decreases from Stages II to III, the phase which preceded major increases in both polar and neutral lipids in the ovaries. Cholesterol content did not vary during maturation in either organ, in the ovary or midgut gland. Major fatty acids in the ovaries [16:0, 16:1 (n-7), 18:1 (n-9), 18:1 (n-7), 18:2 (n-6), 18:3 (n-3), 20:4 (n-6), 20:5 (n-3) and 22:6 (n-3)] did, however, accumulate significantly at later stages of maturation. It is noteworthy that arachidonic acid [20:4 (n-6)] content remained constant during all stages of maturation but decreased significantly in total polar lipids in the later phases of maturation. In contrast, eicosapentaenoic acid [20:5 (n-3)] increased significantly in all lipid fractions in the later stages, and docosahexaenoic acid [22:6 (n-3)] remained constant in the polar lipids and increased during later stages in the triacylglycerol fraction. Major fatty acids in the midgut gland lipids showed significant decreases from Stages II to III, just before the final period of maturation.     

Respiratory impairment by water-borne copper and zinc in the edible crab cancer pagurus (L.) (Crustacea: Decapoda) during hypoxic exposure

Specimens of the edible crab Cancer pagurus (L.) collected in the Skagerrak, Denmark, between June and August 1990 were examined in the laboratory. Impairment of respiratory function after pre-exposure (7 d) to sub-lethal concentrations of Cu and Zn (0.4 mg l^-1) was only detectable during hypoxic exposure [PO₂ (partial pressure of oxygen) =60 torr]. This was indicated by a decrease in the transfer factor (TO₂), due principally to an increase in the PO₂ differential across the gills. Cu and Zn exposure did not cause significant changes in ventilation or perfusion although there was some indication that cardiac output may increase in respiratory-impaired individuals. After 28 d exposure no difference was noted in the respiratory responses to hypoxia of treated and untreated crabs. It is concluded that respiratory impairment was due to an increase in the diffusion barrier thickness at the gills and that this was reversible even during continued exposure to trace metal contamination.     

Effect of hypophyseal gonadotropins (FSH and LH) on the ovaries of the sand shrimp Crangon crangon (Crustacea: Decapoda)

The effect of purified preparations of ovine hypophyseal gonadotropins NIH-FSH-S12 and NIH-LH-S19 on the histological structure of the ovaries of the sand shrimp Crangon crangon (L.) (Crustacea: Decapoda) was studied. All experiments were carried out on sexually mature females, out of the breeding season. The individuals treated with the gonadotropins included intact females as well as those in which the eyestalks were ligated to eliminate a source of gonad-inhibiting hormone (GIH). The results obtained indicate that both FSH and LH have a stimulating effect on the ovaries of the common shrimp, FSH causing growth in the number of somatic cells of the ovary, and LH — meiosis in the sex cells. The effect of each of the 2 gonadotropins was similar in intact and eyestalkless females which indicates its independence from the presence or absence of GIH. The response of crustacean ovaries to mammalian FSH and LH indicates that gonadotropins may act upon invertebrates.     

New insight on population genetic connectivity of widespread amphidromous prawn Macrobrachium lar (Fabricius, 1798) (Crustacea: Decapoda: Palaemonidae)

Due to the sparse and unstable nature of insular freshwater habitats, marine larval dispersal of amphidromous species is considered a critical element of population persistence. We assessed population genetic structure of freshwater prawn Macrobrachium lar across its range that encompasses two biogeographic barriers: the vast open ocean separating Western and Central Pacific regions and the Indo-Malay archipelago separating Indian and Pacific oceans. A total of 173 samples collected from 21 islands throughout the Indo-Pacific were sequenced at 16S and 28S rDNA. We observed distinct genetic isolation of populations located at the eastern and southwestern edge of the species range but no evidence of an effect of the Indo-Pacific barrier. Differentiation patterns are consistent with a stepping-stone model of dispersal. Genetic differences of Central Pacific populations may reflect founder events associated with colonization of isolated islands, or be a signature of a past bottleneck after population depletion caused by drastic climatic events.     

Allozyme and mitochondrial DNA variation in Cuban populations of the shrimp Farfantepenaeus notialis (Crustacea: Decapoda)

We investigated the genetic diversity among populations of the shrimp Farfantepenaeus notialis, the most abundant penaeid species around Cuba. A total of 25 allozyme loci were analyzed in samples of shrimps from seven localities at the south central platform of the island (Ana María Gulf). Samples from three of these localities and from Batabanó Gulf and Guacanayabo Gulf at the south west and south east platforms of the island, respectively, were also characterized at the mtDNA level through sequence variation of a 2027 bp segment including part of the COI and COIII genes. Of the 25 allozyme loci studied 9 were polymorphic: Akp2, Akp3, AmyB, Est3, Gdh, GP7, and Per1, 2 and 3. In contrast to mtDNA, the pattern of allozyme variation among localities revealed strong population structuring at Ana María Gulf, with significant F _st in all pairwise comparisons. The magnitude of F _st estimates as well as the grouping pattern obtained by a UPGMA analysis based on a distance matrix indicated that the level of differentiation was concordant with the geographical position of the localities and the hydrographic regime. Homogeneity of mtDNA suggested that differentiation of allozyme loci might be due to more recent events rather than historical isolation of the sampled populations. Ana María and Guacanayabo Gulf populations were differentiated by mtDNA from Batabanó Gulf, at the southwestern end of the island. The analysis showed three restriction site differences among them, suggesting genetic isolation of the two regions. The present results also suggest that an artificial introduction of larvae from Tunas de Zaza into Batabanó Gulf, in an effort to repopulate this fishing region, may have been ineffective. Received: 13 December 1999 / Accepted: 2 October 2000     

Differential utilization of biochemical components during larval development of the spider crab Maja brachydactyla (Decapoda: Majidae)

Changes in lipid class, fatty acid, fat-soluble vitamins, amino acid and minerals were studied during larval development of Maja brachydactyla Balss, 1922 in order to provide information of its ontogeny and evaluate possible dietary deficiencies and constraints. Four different batches were analyzed from hatching to metamorphosis using enriched Artemia as food. Cultured larvae were in a good nutritional condition as confirmed by the continuous lipid accumulation throughout ontogeny. A regulation of polyunsaturated fatty acids (PUFA) occurred during development in order to maintain adequate basal levels of ω-3 fatty acids (likely through a retro conversion of C₂₀ and C₂₂ into C₁₈ PUFA). Variations in the tocopherol levels indicated its possible role in PUFA protection against oxidation. Essential amino acid balance during development was not correlated with the Artemia feeding regime, but rather reflected inherent variations of the own species ontogeny. Larval requirements in essential minerals were fully supplied by the enriched Artemia.     

In-situ studies on the life cycle of Diastylis rathkei (Cumacea: Crustacea)

Aspects of the life cycle of the cumacean Diastylis rathkei Kröyer, the most important food item of demersal fishes in the Western Baltic Sea, were investigated from the Underwater Laboratory (UWL) Helgoland in Lübeck Bay. In August the population density was 10.1±3.6 individuals 100 cm^-2 in fine-medium sand (Md=292 m), and 3.6±2.4 individuals in coarser medium sand (Md=470 m). In both substrata, abundance values decreased until October, at each station to a different extent. Particular attention was paid to vertical migrations of D. rathkei. Plankton catches and numerous direct observations provided evidence that the pelagic phase, observed at night, is always combined with ecdysis. During short periods of high swarming and moulting activities, the population structure changed considerably: juveniles of the 3rd stage dominated in early August; thereafter they were replaced by prematures, the last juvenile stage. The first mature individuals were observed in October. Some data are given on growth rate.