Maja Brachydactyla Research Articles

Assessment of the effects of confinement in the spider crabMaja brachydactylaBlass, 1922 broodstock

Adults from spider crab, Maja brachydactyla, Balss, 1922 were kept in captivity for up to 2 years. Haemolymph of ten females was extracted monthly for monitoring several metabolites and the presence of Vibrionacea bacteria. A neurotoxic marker and hepatic metabolic and digestive enzyme capacities were contrasted between wild specimens and those reared in captivity. As a result, no differences were observed in hepatosomatic index (HSI) between males and females, but captive animals presented lower HSI than the wild ones. After 2 years of confinement, no changes in quantities of haemolymph microflora and metabolites were observed and this was considered indicative of adaptation of the broodstock to confinement. Spider crab also showed a large plasticity in their hepatopancreatic digestive capabilities suggested by the adaptation to the food supplied in captivity. Moreover, captivity conditions did not seem to negatively alter their antioxidant defences, xenobiotic capacity or neuromuscular activity, as no enhanced oxidative stress damage was shown in either males or females. These results indicate that although the confinement conditions used in this study do not mimic those from the wild, they could be considered as adequate for rearing M. brachydactyla in captivity, at least with regard to the set of parameters assessed.

Consistent habitat segregation between sexes in the spider crabs <em>Maja brachydactyla</em> and <em>Maja squinado</em> (Brachyura), as revealed by stable isotopes

Differences in the resource use patterns of males and females of the spider crab species Maja brachydactyla Balss, 1922 and M. squinado (Herbst, 1788) from several geographic areas (three in the Atlantic and two in the Mediterranean) were studied through the analysis of stable isotopes of carbon and nitrogen in the exoskeleton of post-pubertal (adult) specimens. Results confirmed that males and females from the same population usually did not differ in δ 15 N values and hence foraged at the same trophic level. In contrast, females were usually enriched in 13 C as compared with males from the same population, thus suggesting that females use shallower habitats than males before the terminal moult. The results reported here also indicate that stable isotop.

First results of embryonic development, spawning and larval rearing of the Mediterranean spider crabMaja squinado(Herbst ) under laboratory conditions, a candidate species for a restocking program

The Mediterranean spider crab, Maja squinado, is depleted due to overfishing. The crab has virtually disappeared from areas where it was abundant, such as the Balearic Islands and the Catalan coast. Maja squinado, is economically and ecologically very valuable, and it is essential to obtain information on its biology and rearing conditions to attempt to repopulate the damaged stocks of the species in the Mediterranean basin. Herein, we describe the first successful rearing of M. squinado under laboratory conditions. Our results show that M. squinado is an excellent candidate for restocking using cultured juveniles. Two consecutive broods with a 1–4 day interbrood period were observed in the laboratory in wild-caught females, the maximum observed duration of embryonic development of the egg mass being 32 days at 18.4 ± 0.9°C, and went through four different stages. The complete larval and first juvenile development was studied in laboratory cultures fed enriched Artemia metanauplius. At 19.6 ± 0.6°C, development from hatching to first crab moult took 17 days, and it comprised two zoeae stages and one megalopa stage. The survival rate at the different stages was monitored, and 7.13 ± 2.3% was achieved at the first crab instar.

Identification of vasa, a potential marker of primordial germ cells in the spider crab Maja brachydactyla, and its expression during early post-embryonic development

A partial sequence of the vasa gene (Mb vasa) has been isolated from the testis of spider crab (Maja brachydactyla). It has been identified as the homologue of vasa based on the deduced amino acid sequence, phylogenetic analysis and tissue-specific expression in adult gonads. Quantitative PCR analysis of Mb vasa during early post-embryonic development (three larval stages and first juvenile crab) found expression at low, but detectable levels. During larval development, expression levels increased slightly, while expression after moult during metamorphosis to first juvenile crab was significantly higher as compared to all larval stages. Overall, the pattern of expression of Mb vasa during early post-embryonic development fits an exponential growth curve, which might be either due to an increase in number or in activity of germ cells, especially after moult to first juvenile instar.

Spatial structure of the spider crab, Maja brachydactyla population: Evidence of metapopulation structure

Distribution and spatial population structure of the spider crab, Maja brachydactyla, in the Ría de A Coruña (NW Spain) and adjacent coastal area was analysed. Sampling was done with experimental traps placed in three shallow bottom sampling stations and the central channel of the Ría, from December 1997 to November 1999. Crabs were tagged to study their movements on a small scale (1–10 km). Mean catches were substantially higher in the inner Ría station (Bastiagueiro) and were significantly higher in sandy substrates. Crabs inhabiting rocky bottoms moved to sandy bottoms from summer to autumn. Two local populations comprising mainly juveniles were identified —one located in Bastiagueiro and the other in Canide. There was no evidence of any major exchange between the juveniles of the two populations nor were juveniles observed to move towards deeper zones. Most of these juveniles reached maturity in summer and migrated to deeper waters. Adult catches and the recaptured specimens from both the experimental sampling and the commercial fishery indicate that the local Bastiagueiro population contributes a much greater number of individuals to the adult crab population in deep waters than does the Canide population. The spatial structure of the population of M. brachydactyla in the Ría de A Coruña may be defined as a part of a postlarval metapopulation made up of two shallow water local juvenile crab populations that migrate to deeper waters after attaining maturity. A pool of adults (and indirectly of larvae) from several local populations is formed in deeper waters. There is strong evidence that local populations are linked by larval dispersal.

Direct evidence of parasitism by Copidognathus stevcici (Acari, Halacaridae) in crabs Maja squinado and M. brachydactyla (Brachyura, Majidae) in the laboratory

Marine mites belonging to the family Halacaridae were found associated with adult females of the spider crabs Maja brachydactyla Balss, 1922 and M. squinado (Herbst, 1788) held under laboratory conditions. Morphological study of collected samples identified the mites as Copidognathus stevcici Bartsch, 1976. C. stevcici was found on pleopods of ovigerous and post-ovigerous females in both crab species, with an intensity ranging from 10 to 326 mites per host. Mites were observed alive on their host for extended periods and direct evidence of feeding on crab's eggs is provided. The COI mtDNA sequence of these mites is reported as an addendum to the species description.

Growth and survival of juvenile spider crabs, Maja brachydactyla (Balss, 1922), fed with fresh or frozen mussels

The effects of diet freezing on the growth, survival and biochemical composition of the diets and juvenile spider crabs (Maja brachydactyla) were studied. Fresh and frozen (at −20 °C for 21 days) mussels, Mytilus edulis, were used as food. Two experiments were conducted and in each, spider crabs were placed in individual trays. During experiment I, 40 juvenile spider crabs (2 months old) were used. Twenty animals (9 ± 2 mg) were fed fresh mussels, and 20 animals (8 ± 2 mg) were fed frozen mussels. Spider crabs fed fresh mussels grew larger than the ones fed frozen mussels (304.0 ± 118.0 and 70.0 ± 40.1 mg respectively). During experiment II, 16 juvenile spider crabs (5 months old) were used. Eight animals (3.4 ± 0.8 g) were fed fresh mussel and eight animals (4.1 ± 1.3 g) were fed frozen mussel. Spider crabs fed with fresh mussels were larger than the ones fed with frozen mussels (92.5 ± 41.7 and 41.5 ± 17.7 g respectively). There were no significant differences in the protein, amino acids and fatty acid composition between fresh and frozen mussels. The freezing procedure makes mussels less adequate for the culture of 2-month-old early juveniles of M. brachydactyla up to 5 months, although they promoted acceptable growth and good survival in older animals (>5 months old).

Specific dynamic action affects the hydrostatic pressure tolerance of the shallow-water spider crab Maja brachydactyla

The bathymetric distribution of marine benthic invertebrates is likely governed by a combination of ecological and physiological factors. The present study investigates oxygen consumption and heartbeat rate in response to attempted feeding at 1, 100 and 150 atm in the shallow-water spider crab, Maja brachydactyla, from temperate European waters. No significant difference was evident between the resting heartbeat rate of specimens at 1 or 100 atm, which were 56 and 65 bpm, respectively (Mann-Whitney, U = 5382.0; n = 95, 98; p = 0.079). However, at 150 atm the resting heartbeat rate was significantly higher than that observed for 100 atm at 108 bpm (Mann-Whitney, U = 49.0; n = 45, 98; p < 0.001). At 150 atm, feeding was never observed and coupled with the elevated resting heartbeat rate; it is suggested by 150 atm continued survival is unfeasible. At 1 and 100 atm, feeding instigated a distinct increase in heartbeat rate, which remained elevated for over 30 h. This increase peaked within 1 h at 1 atm. At 100 atm, this required 4 h and postprandial oxygen consumption was significantly higher than at 1 atm (Kruskal-Wallis, H = 85.036; df = 2; p < 0.001). Elevated hydrostatic pressure is hypothesized to extend the duration and the total metabolic energy devoted to specific dynamic action. The metabolic requirements of feeding under hyperbaric conditions may even reach such a critical demand that feeding is entirely inhibited.

Replacement of live prey by formulated diets in larval rearing of spider crab Maja brachydactyla

Preliminary experiments on the replacement in live prey by a formulated microbound diet (MBD) were carried out during larval development of the spider crab, Maja brachydactyla. Four levels (25, 50, 75 and 100%) of replacement of live prey (enriched Artemia metanauplii, EAM) were tested throughout larval development (zoea I = ZI, zoea II = ZII and megalopa = M). Replacement of up to 50% had no significant effect on the growth rate and survival of the larvae during any stage. Total replacement (100% MBD) resulted in a decrease in larval dry weight suggesting a poor assimilation of the proteins and lipids of the MBD. Survival of the larvae fed with the MBD did not appear to be affected, as it was significantly higher than the unfed control. Digestive enzyme activity (protease and amylase) of the larvae was probably influenced by both the physiological response to the formulated diet and larval ontogenetic changes. Further research is needed to improve MBD digestibility and to establish the lipid requirements of the larvae.

Changes between consecutive broods in the fecundity of the spider crab, Maja brachydactyla

Abstract Verísimo, P., Bernárdez, C., González-Gurriarán, E., Freire, J., Muiño, R., and Fernández, L. 2011. Changes between consecutive broods in the fecundity of the spider crab, Maja brachydactyla. – ICES Journal of Marine Science, 68: . An analysis of the fecundity of Maja brachydactyla and the possible causes for its variability was carried out during two breeding cycles in the Ría de Arousa (Galicia, NW Spain). Based on brood samples with known weight data, subsample counts were taken of the number of eggs (125 081–530 309 eggs), and dry weight and volume of individual eggs were recorded. The main cause of variability in egg number and dry weight of the broods was female body length. Moreover, the size of the broods during the two breeding cycles and of subsequent broods exhibited significant differences in terms of both fecundity (p &lt; 0.05) and brood dry weight (p&lt; 0.05). The first broods contained fewer, larger eggs (a greater energy investment per egg), whereas subsequent broods contained more, smaller eggs (less energy investment per egg).

Annual variation in the biochemical composition of newly hatched larvae of Maja brachydactyla in captivity

Quality of newly hatched larvae (NHL) of Maja brachydactyla in captivity has been characterized throughout the year to evaluate their availability for mass production. Spawning took place every month and NHL were collected and analyzed to estimate individual dry weight (DW) and proximate biochemical composition (protein, carbohydrate and lipids). Lipid class, fatty acid composition, amino acid profile, mineral and vitamins A, E and C contents were analyzed seasonally. NHL obtained throughout the year are a potential source for aquaculture purposes, since the increment in the relative protein and lipid (especially phospholipids and n-3 PUFA) content might compensate the decrease in DW of larvae hatched from broodstock kept during one year in captivity. However, the decrease in vitamins A and E as well as in certain essential amino acids (Lys, Val, and His) and trace elements (Cu and Fe) of NHL at the end of the year might be indicative of a nutritional deficiency in broodstock diets.

Diversity of vibrios in the haemolymph of the spider crab Maja brachydactyla

The aim of this study was to characterise and identify vibrios isolated from the haemolymph of apparently healthy adult spider crabs (Maja brachydactyla) wild-caught in the Spanish localities of Galician coast and in the Canary Islands and also from captive animals held at IRTA's facilities in the Ebro Delta of Catalonia, north-west Spanish Mediterranean coast. A total of 277 bacterial isolates were obtained, and of these, 171 were characterised with rep-PCR, resulting electrophoretic bands were analysed and clusters formed. Identification of representative strains of each cluster was made by sequencing the 16S rRNA. Samples from animals caught in Galicia and captive at IRTA (around 15-18°C) rendered mostly species belonging to the Splendidus clade (72·2 and 76·6% respectively), commonly found in cold waters (below 20°C). Higher species diversity was found in the haemolymph of the captive animals. In the warmer Canary Islands waters (around 21°C), the diversity of vibrios is dominated by three clades, Harveyi (Vibrio core group, 39·3%), Orientalis (23·2%) and Splendidus (21·4%) with a species diversity that equals that of the colder captive animals. Differences in the vibrios populations were found in the haemolymph extracted from animals collected from the three localities. Potential new species were found, and their description is under way. As with other invertebrates, spider crabs also contain a diverse population of vibrios. These findings should help researchers to diagnose when a crab is infected.

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.

Effect of delayed first feeding on larval performance of the spider crab Maja brachydactyla assessed by digestive enzyme activities and biometric parameters

The effect of food deprivation on larval performance of the spider crab Maja brachydactyla was studied in terms of survival, moulting capacity, size, weight and enzymatic activities. Five feeding treatments that differed in the initial age of first feeding larvae (fed from hatching, 2, 4 and 6 days post-hatching and unfed) were tested for 20 days. Newly hatched larvae kept without food supply lasted for 10 days and did not moult; with 50% survival observed at 6 days post-hatching. Larvae (zoea I stage) were only able to tolerate 2 days of food deprivation after the onset of exogenous feeding without their performance being compromised. Multivariate analyses suggest that digestive enzyme activities may be good indicators of the nutritional condition of larvae.

Development and growth of the early juveniles of the spider crab Maja squinado (Brachyura: Majoidea) in an individual culture system

The spider crab Maja squinado is an endangered Mediterranean species; therefore, culturing it successfully is essential for developing restocking programs. The survival, growth and development of post-larval stages (juvenile crabs, C1–C8) were studied using larvae obtained from adult individuals collected in the Catalan Sea. The juvenile crab stages were cultured individually from a megalopal stage using a semi-open recirculation system to obtain the precise growth data of each juvenile crab stage until C8. Development up to C8 at 20 °C lasted 154 ± 10 days. Survival from C1 to C8 was 5.8%. Moult increment values in cephothoracic length were similar in all the crab stages (21–35%). Intermoult duration (9 ± 1 in C1–C2 to 51 ± 8 days in C7–C8) increased sharply from juvenile stage 5. Males and females can be distinguished from C4 based on sexual dimorphism in the pleopods and the presence of gonopores. The allometric growth of the pleon is sex-dependent from C4, with females showing positive allometry and males isometric growth. The juvenile growth rate was lower compared with that of the previously studied Atlantic species Maja brachydactyla.

Ontogenetic changes in digestive enzymatic capacities of the spider crab, Maja brachydactyla (Decapoda: Majidae)

Ontogenetic changes in digestive capabilities were analyzed in larvae and first juveniles of the spider crab Maja brachydactyla. Activities of five proteinases (total proteases, trypsin, chymotrypsin, pepsin-like and aminopeptidase), three carbohydrases (amylase, maltase and chitinase), an esterase and an alkaline phosphatase were studied to evaluate digestive enzyme profiles of the species. Both quantitative (spectrophotometry and fluorometry) and qualitative (SDS-PAGE) approaches were used. All assayed enzymes were active from hatching (zoea I-ZI) throughout larval development and in first juveniles. Significant variations during ontogeny were found only in total activities likely as a consequence of digestive system development. Specific activity varied little over ontogeny, being significant only for chitinase. Total proteases, trypsin and pepsin-like activities showed a similar pattern of increase as larval ontogeny advanced, decreasing significantly in juveniles. Chymotrypsin continued to increase, showing maximum activity after metamorphosis. Proteinase zymograms confirmed strong proteolytic activity in first zoeas, with increasing bands over the course of ontogeny, decreasing after metamorphosis. A group of bands with high molecular mass was specific to larval stages. Amylase and maltase showed a parallel pattern of continuous increase of total activity as development advanced. Gel-SDS-PAGE showed unchanged patterns of amylase activity in first zoeas of different ages and the most complex set of bands during larval ontogeny in second zoea. Esterase total activity increased significantly as ZI's aged likely reflecting introduction of a lipid-enriched diet. The importance of lipid accumulation at the beginning of ontogeny was also confirmed by the protease/esterase and amylase/esterase activity ratios, which decreased from hatch to late ZI and might be explained as an adaptation, ensuring the next molt. The results suggest that larvae of M. brachydactyla are capable of digesting a variety of dietary substrates as soon as they hatch.

Dynamics of the Small-Scale Spatial Structure of a Population of the Spider CrabMaja brachydactyla(Decapoda: Majidae)

ABSTRACT Spider crab (Maja brachydactyla) juveniles inhabit shallow coastal areas until they reach maturity and start a mating migration toward deeper waters. Small-scale spatial distribution was analyzed for a shallow-water local population using data from a monthly trap sampling study conducted from December 1997 to November 1999. The trap arrangement formed a grid covering a total area of 3.2 km2. Catch per unit of effort (CPUE) for each biological category (defined by sex and maturity status) was modeled using geostatistics to analyze the spatial structure and to map distribution. Juveniles showed persistent aggregations roughly 150–300 m in diameter and no large-scale movements. Juvenile patches were highly stable in time. During summer, some of the juveniles attained sexual maturity and the aggregation broke up. It was reestablished in September and October, when new juveniles recruited. Adults found in shallow waters did not show a clear spatial structure. The relation variance per mean CPUE was us...

Photobacterium swingsii sp. nov., isolated from marine organisms

Six Gram-negative coccobacilli were isolated from Pacific oysters (Crassostrea gigas) from Mexico and haemolymph of spider crabs (Maja brachydactyla) from Spain. All of the isolates grew as small green colonies on thiosulphate-citrate-bile salts-sucrose (TCBS) agar and were facultatively anaerobic, oxidase-positive and sensitive to the vibriostatic agent O/129. Repetitive palindromic PCR analysis revealed a high degree of genomic homogeneity among the isolates. Several phenotypic traits differentiated the isolates from the type strains of species of the genus Photobacterium. DNA-DNA relatedness between two representative isolates and their closest phylogenetic neighbours by 16S rRNA gene sequence similarity, Photobacterium aplysiae CAIM 14(T) and Photobacterium frigidiphilum CAIM 20(T), was 44.01-53.85 %. We propose a novel species of the genus Photobacterium to accommodate the six isolates, with the name Photobacterium swingsii sp. nov. The type strain is CAIM 1393(T) (=CECT 7576(T)).

Chemical composition of Atlantic spider crab Maja brachydactyla: Human health implications

The Atlantic spider crab Maja brachydactyla is highly appreciated and widely consumed in Southern European countries. Because there is a lack of nutritional information concerning this species, this study aimed to characterize the chemical composition of muscle, hepatopancreas and gonads of M. brachydactyla and to analyze the health implications for consumers. All tissues were valuable sources of high quality proteins, amino acids (e.g. glutamic acid, aspartic acid, arginine, leucine and taurine) and macro and trace elements (e.g. Na, Cl, Cu, Zn and Se). Muscle and gonads were particularly richer in essential polyunsaturated fatty acids (e.g. 20:5 n-3, 22:6 n-3), and had lower fat, calories, Ca, Fe, Cd, saturated and monounsaturated fatty acids than hepatopancreas. Low to moderate cholesterol values were found in all tissues. Consequently, the consumption of the muscle and gonads of Atlantic spider crab is adequate for cholesterol-restricted, low fat, balanced and safe meat diets to meet consumers’ requirements. In contrast, hepatopancreas consumption is not recommended in such diets due to the high levels of fat, energy, Cd, and saturated and monounsaturated fatty acids.

Characterization of larval moulting cycles in Maja brachydactyla (Brachyura, Majidae) reared in the laboratory

The moulting cycles of all larval instars (zoea I, zoea II, and megalopa) of the spider crab Maja brachydactyla Balss 1922 were studied in laboratory rearing experiments. Morphological changes in the epidermis and cuticle were photographically documented in daily intervals and assigned to successive stages of the moulting cycle (based on Drach's classification system). Our moult-stage characterizations are based on microscopical examination of integumental modifications mainly in the telson, using epidermal condensation, the degree of epidermal retraction (apolysis), and morphogenesis (mainly setagenesis) as criteria. In the zoea II and megalopa, the formation of new setae was also observed in larval appendages including the antenna, maxillule, maxilla, second maxilliped, pleopods, and uropods. As principal stages within the zoea I moulting cycle, we describe postmoult (Drach's stages A–B combined), intermoult (C), and premoult (D), the latter with three substages (D 0, D 1, and D 2). In the zoea II and megalopa, D 0 and D 1 had to be combined, because morphogenesis (the main characteristic of D 1) was unclear in the telson and did not occur synchronically in different appendices. The knowledge of the course and time scale of successive moult-cycle events can be used as a tool for the evaluation of the developmental state within individual larval instars, providing a morphological reference system for physiological and biochemical studies related to crab aquaculture.