Search

Simple Summary: On one hand, the females of some crabs can store the sperm from copulations for several years. On the other hand, it is reported that DNA repair mechanisms in sperm cells are less effective than in other cells. Taking into account these two considerations, we conducted a study into the viability and possible genetic damage of DNA in spermatozoa stored in female spider crabs for up to 14 months. The results show that during the first 3–4 months, both the viability and the DNA integrity fall considerably. Natural populations of the spider crab Maja brachydactyla constitute a fishery resource of great economic importance in many countries. As in the rest of eubrachyurans, the females of this species have ventral-type seminal receptacles where they store sperm from copulations. Sperm can be stored in these structures for months and even years before egg fertilisation, with the consequent degradation of the sperm cells during the time. In this work, we analyse the viability and the possible genetic damage in sperm accumulated in the seminal receptacles of M. brachydactyla females as a function of the storage time (from 0 to 14 months) using the comet assay technique. On one hand, we developed an algorithm for comet image analysis that improves the comet segmentation compared with the free software Open comet v1.3.1 (97% vs. 76% of detection). In addition, our software allows the manual modification of the contours wrongly delimited via the automatic tool. On the other hand, our data show a sharp decline in sperm viability and DNA integrity in the first four months of storage, which could lead to a decrease in the fecundity rate and/or viability of the embryos or larvae from the second and third clutches of the annual cycle if the repair capacity in these gametic cells is low. [ABSTRACT FROM AUTHOR]

Natural populations of the spider crab Maja brachydactyla constitute a fishery resource of great economic importance in many countries. As in the rest of eubrachyurans, the females of this species have ventral-type seminal receptacles where they store sperm from copulations. Sperm can be stored in these structures for months and even years before egg fertilisation, with the consequent degradation of the sperm cells during the time. In this work, we analyse the viability and the possible genetic damage in sperm accumulated in the seminal receptacles of M. brachydactyla females as a function of the storage time (from 0 to 14 months) using the comet assay technique. On one hand, we developed an algorithm for comet image analysis that improves the comet segmentation compared with the free software Open comet v1.3.1 (97% vs. 76% of detection). In addition, our software allows the manual modification of the contours wrongly delimited via the automatic tool. On the other hand, our data show a sharp decline in sperm viability and DNA integrity in the first four months of storage, which could lead to a decrease in the fecundity rate and/or viability of the embryos or larvae from the second and third clutches of the annual cycle if the repair capacity in these gametic cells is low.

Abstract The common spider crab Maja brachydactyla is an important wild marine resource in many countries in the NE Atlantic region that also has potential in aquaculture. The larval cycle has been replicated successfully in captivity, with highest mortality evident during larval settlement and metamorphosis to first juvenile stage. As an approximation to understanding natural settlement requirements of this species, we examined the need for individual culture to produce first juveniles in the hatchery. In addition, we assessed whether presence of adult exudates and/or a number of different settlement substrates (natural and artificial) influenced larval settlement and metamorphosis under laboratory conditions. Our data demonstrate that M. brachydactyla megalopae reared in communal culture showed similar survival and shorter developmental duration into juvenile crab when compared to individual culture. Presence of adult exudates did not influence the larval survival or development duration to metamorphosis. Survival was not different between control conditions (absence of substrate), artificial substrata (100 to 1000 μm nylon mesh) or natural substrates except for "mud" substrate where no larvae survived to first juvenile stage in this treatment. Duration of the megalopa stage was also not influenced by type of substrate added (natural or artificial) or to a control (no substrate). Results in the present study indicate that M. brachydactyla culture will not require provision of special requirements since communal larval rearing is an efficient and low cost viable strategy and specific exudates or substrates are not required to produce juveniles. Highlights • The production of Maja brachydactyla juveniles is possible employing low cost technologies. • The juvenile production can be realized under mass culture conditions. • The mass production of juveniles is available without special requirements, i.e. adult odours or substrates. [ABSTRACT FROM AUTHOR]

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 δ15N values and hence foraged at the same trophic level. In contrast, females were usually enriched in 13C 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.

Ten Gram-negative, rod-shaped and motile bacterial strains were isolated from spider crab (M27.10, M27.11a, F36.1, F36.4, M56.1, F76.17b, M146.1, M166.3 and M166.6) and pullet carpet shell clam (SBRF 1.10) collected in the coast of Galicia. Analyses of the 16S rRNA genes showed that the strains belong to the genus Kiloniella and have high similarity with the species Kiloniella spongiae (99.44–99.86%) and Kiloniella litopenaei (99.0–99.5%). Strains M56.1 T (=CECT 9195, =LMG 29925), M146.1 (=CECT 9193, =LMG 29926) and SBRF 1.10 (=CECT 9194, =LMG 29927) were selected on the basis of genotyping by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR). Phylogenetic analysis based on concatenated sequences of the genes gyrB , ftsZ , rpoD and mreB showed that the isolates form a differentiated branch within the genus Kiloniella. Moreover, the average nucleotide identity (ANIm, ANIb and OrthoANI) and in silico estimated DNA–DNA reassociation values between selected Galician isolates and Kiloniella species were below the established cut-off for species deliniation. The results obtained in the genetic and phenotypical analyses indicate that the isolates represent a new species of the genus Kiloniella , for which the name Kiloniella majae sp. nov. is proposed with strain M56.1 T (=CECT 9195 T , =LMG 29925 T ) as the type strain. [ABSTRACT FROM AUTHOR]

The post-larval development of the majid crab Maja brachydactyla Balss, 1922 was studied using laboratory-reared larvae obtained from adult individuals collected in the NE Atlantic. The morphology of the first juvenile stage is described in detail, while the most relevant morphological changes and sexual differentiation are highlighted for subsequent juvenile stages, until juvenile 8. The characteristic carapace spines of the adult phase are present in the first juvenile stage, though with great differences in the degree of development and relative size. The carapace shows a high length/weight ratio, which becomes similar to that of adults at stage 7-8. Males and females can be distinguished from juvenile stage 4, based on sexual dimorphism in the pleopods and the presence of gonopores. In addition, the allometric growth of the pleon is sex-dependent from juvenile stage 4, with females showing a positive allometry (b=1.23) and males an isometric allometry (b=1.02).

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. [ABSTRACT FROM AUTHOR]

Abstract: 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 (1–10km). 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

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 < 0.05) and brood dry weight (p< 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). [ABSTRACT FROM PUBLISHER]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Aims: 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. Methods and Results: 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. Conclusions: 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. Significance and Impact of Study: 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. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. 20:5n-3, 22:6n-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. [Copyright &y& Elsevier]

Abstract: 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 (D0, D1, and D2). In the zoea II and megalopa, D0 and D1 had to be combined, because morphogenesis (the main characteristic of D1) 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. [Copyright &y& Elsevier]

Abstract: Spider crab (Maja brachydactyla) is considered a species of potential interest for intensive aquaculture, although physiological studies are necessary before the optimal conditions for its culture can be established. In this paper we develop equations to explain the oxygen consumption of the species as a function of weight (W: 15–1414g), temperature (T: 13.5–27.9°C), sex (S) and daily light–dark cycle (14L/10D to 10L/14D). The measurements were carried out over three days on single animals receiving one meal of mussels to satiation only on the first day of the measurements. The oxygen consumption values were divided into routine (MO2routine), post-prandial (MO2sda), maximum peak (MO2peak) and daily average between 0–24h (MO2; 0–24h), 24–48h (MO2;24–48h) and 48–72h (MO2;48–72h) post-feeding. Feeding led to an increase in oxygen consumption 1.7–7.3 (2.90±1.25) times the routine value, with maximum peaks between 2 and 16h post-feeding (7.94±4.12h) the effect lasting 10–24h (19.80±3.56h). The different levels of oxygen consumption were expressed as lnMO2routine =0.206+0.837lnW +0.302T −0.006T 2 −0.153S, lnMO2sda =0.294+0.736lnW +1.372lnT −0.171S, lnMO2peak =3.032+0.667lnW +0.083T −0.158S and lnMO2; 0–24 h =0.403+0.769lnW +1.305lnT −0.147S, all to a statistically significant degree (P <0.001) and explaining a percentage of variance above 92%. Although some specimens showed higher oxygen consumption during the night, in the overall analysis of the data the light–dark cycle did not have a statistically significant influence. Interspecific comparisons point to lower oxygen consumption rates other fish and cephalopods of aquacultural interest, and similar to that of other crustaceans in the same experimental conditions. [Copyright &y& Elsevier]

The Magharees fishery (Brandon and Tralee Bays in south-west Ireland) is 495 km2 in extent, the majority of this area ≤20 m in depth. Since 1981 it has been occupied by a directed spider crab fishery yielding in some years all of the national catch of Maja brachydactyla. Maximum recorded landings were 336 t in 1999 and effort has numbered up to 10,000 pots annually. Increasing fishing capacity and declining opportunities have accentuated fishing effort on spider crab. This paper describes a catch census undertaken in the fishing season of March to August inclusive, 2000–2007 and a mark–recapture experiment, 2005–2007. A method of ageing the adult moult by attributing a chronology to the rate of erosion of the claw on the dactyl is introduced. Males migrated longer distances, moved into the fishery on a wider trajectory and demonstrated greater wear on the claw than females. Recapture rate of males was twice that of females. The conduct of the fishery changed in its 26 years in existence. Landings became more concentrated in the earlier months of the year and the recent summer fishery was characterized by fewer male captures. Larger males were quickly removed and none >140 mm carapace length survived in the fishery longer than one year. [ABSTRACT FROM PUBLISHER]

Abstract: The morphology and function of the male reproductive system in the spider crab Maja brachydactyla, an important commercial species, is described using light and electron microscopy. The reproductive system follows the pattern found among brachyuran with several peculiarities. The testis, known as tubular testis, consists of a single, highly coiled seminiferous tubule divided all along by an inner epithelium into germinal, transformation, and evacuation zones, each playing a different role during spermatogenesis. The vas deferens (VD) presents diverticula increasing in number and size towards the median VD, where spermatophores are stored. The inner monostratified epithelium exocytoses the materials involved in the spermatophore wall formation (named substance I and II) and spermatophore storage in the anterior and median VD, respectively. A large accessory gland is attached to the posterior VD, and its secretions are released as granules in apocrine secretion, and stored in the lumen of the diverticula as seminal fluids. A striated musculature may contribute to the formation and movement of spermatophores and seminal fluids along the VD. The ejaculatory duct (ED) shows a multilayered musculature and a nonsecretory pseudostratified epithelium, and extrudes the reproductive products towards the gonopores. A tissue attached to the ED is identified as the androgenic gland. [Copyright &y& Elsevier]

Abstract: The effect of an individual culture system on survival and growth of juvenile crab stages 1–8 of the majid crab Maja brachydactyla Balss, 1922 was studied using larvae obtained from adult individuals collected in the NE Atlantic. The juvenile stages were cultured individually from a megalopal stage using a semi-open recirculation system. Forty-eight percent of the megalopae moulted to first juvenile stage. Detailed growth data have been obtained for each juvenile stage. Juvenile development up to juvenile crab stage 8 (C1–C8) at 20 °C lasted 117.5±7.5 days. Survival was high during the whole experiment: 43.75% of C1 survived to perform the moult to C8. Moult increment values (%CL) were similar in all the juvenile stages (27.90–37.04%). Intermoult duration (9.37±1.04 to 33.5±2.64 days) increased sharply from stage 6, and the specific growth rate (SGR) diminished due to the significant increase of the intermoult period. [Copyright &y& Elsevier]

Abstract: The potential use of fluorescent substrates for measuring digestive enzyme activities has been adapted to decapod crustacean larvae and compared to traditional analytical techniques based on spectrophotometry. The ontogeny of three digestive enzymes (trypsin, amylase, and esterase) from the hepatopancreas of Maja brachydactyla has been selected to illustrate the advantages and disadvantages of both spectrophotometric (SP) and fluorometric (FL) methods. The three enzyme activities showed the same pattern with either of the techniques used. Standardised discriminant function coefficients indicated that the stage of development in spider crab larvae was most strongly discriminated by the activity of amylase, whichever method of analysis was considered. The FL method allows the detection of up to three enzyme activities in a single larva (<100 μg dry weight), whereas SP needs more than 20 times this weight. The FL method allows studying the inter-individual variability, while the SP approach only permits one to evaluate the inter-population variability (pool of individuals). Nevertheless, the higher sensitivity of the FL method implies a larger variability in the results compared to SP. There are no differences in feasibility between the two methods when using kinetic analyses. Although data from different experiments assayed by SP methods are easily standardised in units of dry weight or soluble protein concentration, this standardisation is difficult when using FL substrates, since differences between the sensitivity of the equipment used for the analysis might be higher than one order of magnitude. The availability of FL substrates in the market is constantly increasing, although it is still scarce in relation to the high number and types of substrates normally used in SP methods. This may be a limitation to the study of certain enzyme activities. The cost of the analysis is based on the price of the specific substrates, FL substrates being more expensive than SP ones. Both SP and FL methods are useful to measure digestive enzymes in decapod crustacean larvae. Selection of the method used will depend on the objectives and interests of the researcher. For studies based on the characterization of enzyme activities in crustacean populations without any limitation on the number and amount of samples, the SP method is recommended. When several experimental treatments, dietary regimes, and/or moulting stages are considered, the FL analysis might be more appropriate due to the low number of individuals needed for sampling. If the study is conducted to assess the individual variability of the population, then, the FL method needs to be applied. [Copyright &y& Elsevier]

The morphology of the different larval stages (zoea I, zoea II and megalopa) of the majid crab Maja squinado Herbst, 1788 reared under laboratory conditions is described. The description of M. brachydactyla Balss, 1922 larvae is also revised, both from individuals reared in laboratory conditions and those collected from plankton samples. The larval stages of M. squinado are morphologically similar to those of the Atlantic species M. brachydactyla; the larval morphology does not justify the separation of M. squinado into two species. Larvae of M. brachydactyla obtained from the wild were similar to those reared under laboratory conditions. The morphology of the zoeal and megalopal stages of M. squinado and M. brachydactyla described in this paper have been compared with previous descriptions of the genus Maja, including M. brachydactyla (described as M. squinado). [ABSTRACT FROM AUTHOR]

Abstract: The large edible spider crab Maja brachydactyla Balss, 1922, an overexploited coastal fishery resource in Galicia (NW Spain), is considered as a potential aquaculture candidate. Patterns of its larval growth were studied under controlled laboratory conditions (constant 18±1 °C; 36‰ salinity; photoperiod ca. 12:12 h; lipid-enriched Artemia metanauplii provided as food). From hatching through complete larval development and metamorphosis to the first juvenile crab instar, changes in carapace size, dry weight (DW), ash content, elemental composition (carbon, hydrogen, nitrogen; CHN), and proximate biochemical composition (total proteins, lipids, carbohydrates; Pr, L, Ch) were measured in successive stages (zoea I, II, megalopa, crab I). Body size may be described as a linear function of the number of molting cycles, whereas the amounts of DW, CHN, Pr, L, and Ch per individual increased exponentially (3 to 9 fold). The highest growth rates were observed in L, C and H, the lowest in DW, Pr and N. As a consequence of these patterns, the C:N mass ratio as well as the fractions of L, C and H (in % of DW) increased significantly, while those of Pr and N decreased from 26% to 16% of DW. Throughout development, however, Pr remained the principal biochemical component of total DW. Positive correlations between biochemical and CHN data allow for estimates of Pr from N and of L from C values per individual. The patterns of larval growth observed in M. brachydactyla are, in general, similar to those previously described for other brachyuran crabs with a planktotrophic mode of larval development. [Copyright &y& Elsevier]

Abstract: The spider crab Maja brachydactyla is overexploited on the NW coast of Spain. Aquaculture of this species can be the solution to the problem, and consequently, several attempts of intensive larval rearing have been conducted. However, most of the studies already published do not provide enough zoo technical data, especially in terms of larval and prey densities or the nutritional quality of diets used for rearing. Three experiments were carried out to evaluate the conditions for intensive larval rearing of M. brachydactyla. Larval stocking density (10, 50 and 100 larvae L−1), prey:larva ratio (15, 30 and 60 enriched Artemia larva−1) and diet (enriched Artemia, non-enriched Artemia and polychaete supplement) effects on growth and survival of this species were studied. For larval culture nine, 35 L, 150 μm mesh-bottomed PVC cylinders (triplicates for each treatment and larval stage) connected to a recirculation unit, were used. Temperature and salinity were kept constant at 18 °C and 36‰ respectively. A 12 to 18 day trial was conducted for each experiment and samples of larvae were collected at each larval stage (zoea I, zoea II, megalopa) in the inter-molt phase and at first juvenile. Survival, carapace length and width, dry weight (DW), and proximate biochemical content (protein, carbohydrates and total lipid) as well as lipid class composition were determined. Stocking densities of 100 larvae L−1 resulted in higher growth in DW and higher content in lipids and protein for zoea I (ZI) and zoea II (ZII) than 10 larvae L−1. However, survival decreased with increasing stocking density. The use of 60 preys larva−1 produced larvae with significantly higher DW and protein content, especially at ZII stage, than lower prey densities. Survival rate obtained feeding 60 preys larva−1 up to the megalopa stage was almost two-fold (42.2%) the rate obtained using 15 preys larva−1 (24.8%). Larvae fed on enriched Artemia (EA) showed an increase in weight up to megalopa (518.9±26.5 μg) in contrast to larvae fed on non-enriched prey (A) (467.9±6.9 μg). Variation in DW correlated with the total lipid content (L) of the larvae (LEA =70.1±37.5 μg ind−1; LA =28.9±3.2 μg ind−1) especially in terms of neutral lipids. The use of an initial density of at least 50 larvae L−1 and 60 enriched Artemia larva−1 can be considered the most adequate rearing parameters in order to obtain good results in growth and survival of M. brachydactyla. [Copyright &y& Elsevier]

Abstract: The analysis of tissue''s naturally occurring stable carbon and nitrogen isotope ratios is a useful tool to delineate trophic relationships. However, the interpretation of δ 13C and δ 15N is complicated by the influence of multiple factors such as the tissue-specific lipid content. The aim of this work was to evaluate the effects of lipid extraction on δ 13C and δ 15N compositions in muscle, hepatopancreas and gonads of a marine decapod crustacean, the spider crab Maja brachydactyla. Samples were analyzed for stable isotopes before and after lipid removal, using a derived Soxhlet extraction method. Differences in δ 13C and δ 15N were measured among tissues before and after treatment. Lipid extraction of muscle did not have a significant effect on either δ 13C or δ 15N. By contrast, ecologically significant shifts for both carbon and nitrogen stable isotopes ratios (+2.9±0.8‰ for δ 13C, and +1.2±0.7‰ for δ 15N) were noticed in the hepatopancreas. In regard to gonads, lipid extraction led to a shift only on δ 13C (+1.3±0.3‰). Finally, the derived Soxhlet extraction method removed the lipid influence for δ 13C, and had an effect on δ 15N composition for lipid-rich samples. We recommend this treatment for carbon stable isotope studies on decapod crustacean lipid-rich tissues. [Copyright &y& Elsevier]

Abstract: A good sampling method for collecting data on the abundance, spatial and demographic structure of a marine population would enable a researcher to: (1) obtain unbiased abundance estimates (absolute or relative), (2) accurately represent the spatial and demographic structure, and (3) obtain enough samples at a reasonable cost to analyze size-frequency distributions and other demographic parameters. Different methods for estimating the abundance and population structure of the spider crab Maja brachydactyla in the Ría de A Coruña (NW Spain) were assessed. Sampling was carried out with different procedures—tangle-nets, beam trawls, diving and traps. The use of tangle-nets caused serious problems as both the specimens sampled and the gear itself were damaged. These nets also provided less spatial resolution of the small-scale distribution of organisms. Sampling by means of diving in this area was unviable due to limited visibility, high turbulence and strong currents. The catches obtained during monthly samplings using traps and beam trawls in the same area during one yearly cycle (June 1998–June 1999) were compared. Trap catches were much higher, in terms of actual quantities and catch per unit of effort (CPUE), although the seasonal pattern was similar with both methods. A significant linear relationship was found between the trap and beam trawl catches: CPUEtraps =3.34+3.987CPUEtrawl (R 2 =0.54, p =0.02). The beam trawl catches contained a higher proportion of very small crabs (specimens<60mm carapace length, CL, comprised 23% of the total catch taken by beam trawling, compared to only 0.7% when traps were used), and very few large specimens (CL>130mm), especially adults. The catchability of adult crabs using the beam trawl accounted for only 12% as compared to that of traps. The fishing area of a trap was estimated to be 1440m2 for juveniles (CL=70mm). A comparison of these two sampling methods in terms of cost-effective sampling (in days) showed that the beam trawl is almost four times as expensive as the traps, for the same number of organisms collected. [Copyright &y& Elsevier]

The spiny spider crab Maja brachydactyla in an important fishery resource throughout its distribution range (Northeast Atlantic). Here we describe the isolation of nine microsatellite loci for this species. These new markers were tested in 20 crabs from NW Spain. The number of alleles ranged from 3 to 20 and expected heterozigosity from 0.57 to 0.95. All loci followed Hardy-Weinberg expectations except mMb33 and mMb307, which could be affected by null alleles. Some of these loci seem to be better fitted by a multi-step substitution process. [ABSTRACT FROM AUTHOR]