Characterization and comparison of digestive proteinases of the Cortez swimming crab, Callinectes bellicosus, and the arched swimming crab, Callinectes arcuatus

Abstract. Protease activity in the midgut gland, gastric chamber, and gastric juice from the crabs Callinectes bellicosus and Callinectes arcuatus was characterized by several methods, confirming that the composition of digestive proteases is the same in the gastric juice and the midgut gland. Gastric juice was suitable for the identification and characterization of the proteinases trypsin and chymotrypsin. Such enzymes were presented as isotrypsins and isochymotrypsins. Proteinase composition evaluated by SDS-PAGE and substrate-SDS-PAGE showed differences between species, but not between gender. Proteinases were thermostable at 40°–50°C for 1 h and showed maximum activity at pH 6–8, making the use of digestive proteinases for evaluations of protein digestibility by the pHstat method possible. We propose using gastric juice as a source of digestive enzymes for in vitro studies of enzymes in digestibility assays and characterization procedures.     

Feeding activity of Callinectes ornatus Ordway, 1863 and Callinectes danae Smith, 1869 (Crustacea, Brachyura, Portunidae) in Ubatuba, SP, Brazil

The feeding activity along the day cycle and the time consumed for extracellular digestion were evaluated in the portunids C. ornatus and C. danae. Swimming crabs were obtained from trawling in Ubatuba bay, São Paulo, Brazil, during both the rainy and dry seasons. In each season, daily scheduled samples were taken at dawn (±6 h), noon (±12 h), dusk (±18 h) and midnight (±24 h). All individuals were dissected and the degree of stomach replenishment was recorded. In order to estimate the time elapsed for extracellular digestion, crabs were fed, and groups were dissected at 30 min intervals to check the conditions of their stomachs. In general, both species show a higher feeding activity during periods of lower light intensity, as evidenced by an increased percentage of full stomachs in dusk and midnight samples. The obtained results support higher feeding activity at night in these species and indicate short time for extracellular digestion, not exceeding 8 h. Nevertheless, full stomachs were recorded in all sampling schedules. In this case, it should be considered that elimination of certain food items such as fish bones, mollusk shells and carapace fragments of crustaceans could take more time than other items. Additionally, some crab species could require a cycle of cell replacement in the midgut gland epithelium until they can take their next meal.     

Fish and decapod crustaceans inhabiting drifting algae in Jervis Bay,New South Wales

Abstract This study documents the fish and decapod crustaceans inhabiting a bed of Gracilaria verrucosa that was drifting on the bottom of a temperate marine embayment in relatively deep water (15- 18m) during autumn 1991. Fauna were sampled with diver-operated enclosure nets. Relatively few species inhabited the algae at this time, and the assemblage was primarily a subset of that in adjacent Posidonia australis beds. Three fish species [Neoodax balteatus (Odacidae), Cristiceps australis (Clinidae), Siphamia cephalotes (Apogonidae)] and one species of crab [Nectocarcinus tuberculosus (Portunidae)] dominated the catches numerically. A further 14 fish and decapod species were relatively rare. Neoodax balteatus, C. australis and N. tuberculosus were caught at all life stages and appeared to be permanent residents of the Gracilaria. Few juveniles of other species were captured, which indicates that these algal wracks may not be an important nursery habitat for seasonally resident fish species. Trachurus novaezelandiae and a number of other fish species that associate with a variety of benthic habitats appeared to be transient visitors. The biomass of algae varied significantly within the bed, but algal biomass was not a good indicator of faunal abundances. The low species richness of the fish and decapod crustacean assemblage may be related to both lower recruitment in deeper water and to unfavourable characteristics of the alga.     

四种常见蟹类对光棘球海胆的捕食策略

光棘球海胆(Mesocentrotus nudus)是维持海藻生态系统稳定的关键种,同时也是北方重要的经济海胆类.目前对黄渤海地区光棘球海胆的种群生态学研究还不足,对影响其种群数量动态的因素尚不明确.为探明光棘球海胆的捕食者种类及其捕食策略,选择平背蜞(Gaetice depressus)、肉球近方蟹(Hemigrap...     

中国短桨蟹属(十足目,短尾次目,梭子蟹科)二新种

记述梭子蟹科Portunidae,短桨蟹属Thalamita 2新种,即刺肢短桨蟹T.acanthophallus和西沙短桨蟹T.xishaensis.     

Isolation and characterization of microsatellite loci in Portunus pelagicus (Crustacea: Portunidae)

Seven dinucleotide and one tetranucleotide microsatellite loci were isolated and characterized, using routine protocols, from the blue swimmer crab, Portunus pelagicus. These loci will be useful for investigating the population structure of this broadly distributed and economically important portunid. In particular, all eight loci were polymorphic in P. pelagicus collected from throughout Australia. In addition, the genotype frequencies at each locus in each population sample were usually not significantly different from those expected under Hardy–Weinberg equilibrium conditions. Six of the eight loci also showed moderate to high levels of polymorphism in an undescribed species of Portunus from northern Australia.     

Genetic population structure of the swimming crab Callinectes danae (Crustacea: Decapoda) in southern Brazil

The population genetic structure of the swimming crab Callinectes danae (Crustacea, Portunidae) was studied by allozyme electrophoresis along the southern coast of Brazil (Santa Catarina and Rio Grande do Sul States). The biology of C. danae is poorly known, but some studies suggest that this species depends on estuaries for reproduction and for completing its life cycle, using them as recruitment sites and nursery grounds. If estuarine retention is an important process acting in favour of the recruitment of local populations, we should expect restriction of gene flow among populations inhabiting different estuaries. Therefore, our aim was to establish whether gene flow between populations of C. danaefrom different estuaries was restricted. Samples were collected in four estuaries: São Francisco do Sul, Laguna (Santa Catarina), Patos Lagoon and Chuí Stream (Rio Grande do Sul). Eleven loci were resolved. Contingency table tests (² and G) showed significant differences (P0.05) between pair-wise subpopulation comparisons. The estimated F _ST was =0.065±0.019, suggesting a moderate structuring of C. danae populations. No relationship was found for the number of migrants between pairs of subpopulations and the geographic distance separating them (P= 0.292; r ²= 0.269). Nevertheless, UPGMA analysis clustered together those estuaries separated by less than 250 km. Low adult migration, the requirement of estuaries as reproductive areas, recruitment sites and nursery grounds for juveniles, together with larval and post-larval retention processes, are discussed in the context of their importance in preventing panmixia among subpopulations inhabiting different estuaries.     

Distribution,abundance, and feeding of a disjunct population of lady crab in the southern Gulf of St. Lawrence,Canada

The lady crab (Ovalipes ocellatus) is one of the most common native species of swimming crab (Portunidae) of the Atlantic Coast of North America but most populations occur south of Cape Cod, Massachusetts. There is a disjunct population in Northumberland Strait (southern Gulf of St Lawrence), which was the focus of this study. Adult lady crabs were collected by trawling in water >4 m deep from May to October 1999 to 2005 to determine abundance, distribution, and diet. Lady crab occurred only in a small area (about 2,500 km²) in the central part of Northumberland Strait where bottom water temperature was >18°C during summer, and the substrate was mainly sand or sandy gravel. Male lady crab attained a maximum carapace width (CW) of 112 mm compared to 92 mm CW for females. The summer and autumn diet consisted mainly of infauna. The principal prey (each >5% of diet by weight) were: small bivalve molluscs (primarily Atlantic razor clam Siliqua costata and Macoma sp.; 43%), small rock crab (Cancer irroratus; 13%), polychaetes (11%), fish remains (9%), and small lady crab (9%). All stomachs collected during May (water temperature ≤10°C) were empty. There was little evidence of any difference in feeding intensity between 0700 h and 1900 h.     

A comparative study of zoeal morphology in the genus Liocarcinus (Crustacea: Brachyura: Portunidae)

The zoeal morphology of Liocarcinus arcuatus, L. corrugatus and L. depurator is described from laboratory reared material and the larvae of L. holsatus, L. puber, L. pusillus and L. marmoreus are reexamined from specimens deposited in the BM (NH). No single meristic character was found that would adequately separate the seven described species of Liocarcinus. Characters that may facilitate separation of later zoeal stages only are listed.     

First distributional record of Carupella banlaensis from India

The present study describes a new record of the rare portunid crab Carupella banlaensis from Goa, along the central west coast of India, based on carapace and appendage morphology and provides detailed morphometric measurements of two immature female specimens. Carupella banlaensis differs from its congeners in possessing less prominent median and lateral frontal lobes, the first eight anterolateral teeth alternating large and small and bluntly triangular, the cheliped merus with three large spines on the anterior margin and one distal spine on the posterior margin. Previously known only from the Gulf of Tonkin (China) and Somalia, the present observation of this crab is a new record for the entire South Asian region.