Occurrence and abundance of brachyuran larvae in the Manora Channel (Karachi, Pakistan) during 1993

The present paper investigates the occurrence and abundance of brachyuran larvae in the Manora Channel during August- December 1993. The fortnightly planktonic sampling was carried out in Manora Channel which is bordered by mangroves, during day time from surface and subsurface waters at shallow depth using Bongo net of 300 micron mesh size. Analysis of samples revealed presence of brachyuran larvae of 12 species belonging to 6 families. Of these 4 species are confirmed: Serenella indica, Dotilla blanfordi, Metopograpsus thukuhar and Clistocoeloma lanatum, 2 provisionally identified species are: Pilumnus ?karachiensis and Pinnotheres ?pisum, 2 species are identified upto generic level: Philyra sp. and Pinnotheres sp., and 1 Ocypodid species and 3 Xanthid species are identified upto family level. This study based on identification, occurrence and abundance of brachyuran larvae in the area, also gives percentage composition of brachyuran larvae collected during 1993, in the Manora Channel.

Percentage composition of Brachyuran larvae collected during 1994 in Manora Channel, Karachi, Pakistan

Brachyuran larvae are the most common zooplankton component of the Manora Channel, Karachi, Pakistan. The identification of these larvae would assist in the assessment of brachyuran species and provide information on percentage composition, occurrence, abundance and breeding habits of the brachyuran species in the Manora Channel area. However plankton caught larvae is not easily identified. An accurate identification of such material is only possible by the comparison with larvae reared under laboratory conditions and documented with illustrations. The identifications for this present study were based on the works of Gurney (1938); Atkins (1954); Chhapgar (1955); Raja Bai (1960); Hashmi (1969, 1970a, b); Baba and Miyata (1971); Kakati and Sankolli (1975); Rice (1975); Kakati (1977); Lim and Tan (1981); Yatsuzuka and Sakai (1984); Fielder, et al (1984); Amir (1989, M. Phil thesis unpublished); Ingle (1992); Siddiqui and Tirmizi (1992); Tirmizi et al (1993); Bano (1999, M. Phil thesis unpublished); Ghory and Siddiqui (2001); Ghory (2002, M. Phil thesis unpublished); Ghory and Siddiqui (2002).

Distributional patterns of brachyuran larvae in Manora Channel (Karachi, Pakistan) collected during 1995

This study gives an account of distributional patterns of Brachyuran larvae in the Manora Channel from January to November 1995. The planktonic sampling was carried out during day time from surface and sub-surface waters of station I and II (certain sites) at shallow depths (15'-20') using Bongo net of 300 micron mesh size. In all 19527 larvae were obtained through fourteen sampling. These brachyuran larvae belonged to nine families and twenty four species: Ebalia sagittifera, Philyra sp., Philyra scabriuscula (Leucosiidae), Schizophyris aspera (Majidae), Charybdis annulata, Charybdis sp. (Portunidae), Xanthid sp A., B. and C. (Xanthidae), Pilumnus karachiensis, Pilumnus sp. (Pilumnidae), Menippe rumphii (Oziidae), Pinnotheres sp. A, and B. (Pinnotheridae), Nasima dotilliforme, Serenella indica, Macrophthalmus (Mareotis) depressus, Macrophthalmus sp., Dotilla blanfordi, Ocypodid sp. A., B. and C. (Ocypodidae), Metopograpsus thukuhar and Clistocoeloma lanatum (Grapsidae). This study is based on identification, occurrence, distributional patterns along Manora Channel and percentage composition of brachyuran larvae in the area, collected during 1995.

Brachyuran Crabs of Cochin Backwaters- Diversity, Habitat Ecology and Systematics, with special emphasis to Genus Scylla

Among the decapod crustaceans, brachyuran crabs or the true crabs occupy a very significant position due to their ecological and economic value. Crabs support a sustenance fishery in India, even though their present status is not comparable to that of shrimps and lobsters. They are of great demand in the domestic market as well as in the foreign markets. In addition to this, brachyuran crabs are of great ecological importance. They form the conspicuous members of the mangrove ecosystems and play a significant role in detritus formation, nutrient recycling and dynamics of the ecosystem. Considering all these factors, crabs are often considered to be the keystone species of the mangrove ecosystem. Though several works have been undertaken on brachyuran crabs world –wide as well as within the country, reports on the brachyuran crabs of Kerala waters are very scanty. Most of the studies done on brachyuran fauna were from the east coast of India and a very few works from the west coast. Among the edible crabs, mud crabs belonging to genus Scylla forms the most important due to their large size and taste. They are being exported on a large scale to the foreign markets like Singapore, Malaysia and Hong Kong. Kerala is the biggest supplier of live mud crabs and Chennai is the major centre of live mud crab export. However, there exists considerable confusion regarding the identification of mud crabs because of the subtle morphological differences between the species.In this context, an extensive study was undertaken on the brachyuran fauna of Cochin Backwaters, Kerala, India, to have a basic knowledge on their diversity, habitat preference and systematics. The study provides an attempt to resolve the confusion pertaining in the species identification of mud crabs belonging to Genus Scylla. Diversity study revealed the occurrence of 23 species of brachyuran crabs belonging to 16 genera and 8 families in the study area Cochin Backwaters. Among the families, the highest number of species was recorded from Family Portunidae .Among the 23 crab species enlisted from the Cochin backwaters, 5 species are of commercial importance and contribute a major share to the crustacean fishery of the Cochin region. It was observed that, the Cochin backwaters are invaded by certain marine migrant species during the Post monsoon and Pre monsoon periods and they are found to disappear with the onset of monsoon. The study reports the occurrence of the ‘herring bow crab’ Varuna litterata in the Cochin backwaters for the first time. Ecological studies showed that the substratum characteristics influence the occurrence, distribution and abundance of crabs in the sampling stations rather than water quality parameters. The variables which affected the crab distribution the most were Salinity, moisture content in the sediment, organic carbon and the sediment texture. Besides the water and sediment quality parameters, the most important factor influencing the distribution of crabs is the presence of mangroves. The study also revealed that most of the crabs encountered from the study area preferred a muddy substratum, with high organic carbon content and high moisture content. In the present study, an identification key is presented for the brachyuran crabs occurring along the study area the Cochin backwaters and the associated mangrove patches, taking into account the morphological characters coupled with the structure of third maxillipeds, first pleopods of males and the shape of male abdomen. Morphological examination indicated the existence of a morphotype which is comparable with the morphological features of S. tranquebarica, the morphometric study and the molecular analyses confirmed the non existence of S. tranquebarica in the Cochin backwaters.

Brachyuran soft-bottom assemblage from marine shallow waters in the southeastern Brazilian littoral.

The present investigation examined the assemblages of brachyuran crabs in three bays of southeastern So Paulo State, analyzing the numbers of species and individuals, biomass, and diversity. The crabs were collected monthly in Ubatumirim, Ubatuba, and Mar Virado bays in the Ubatuba region over 2 years (1998 and 1999). In each bay, six tows were made from a fishing boat. A total of 39,820 specimens, representing 11 super families, 39 genera, and 65 species of brachyurans, were obtained. The mean number of specimens and biomass varied seasonally, which can be mainly related with the population tendencies of two dominant species in the area (Callinectes ornatus and Hepatus pudibundus). The highest numbers of individuals and species were found in Ubatuba Bay, followed by Ubatumirim and Mar Virado. The highest diversity index was estimated for Ubatumirim (H' = 2.44), followed by Ubatuba (H' = 2.37) and Mar Virado (H' = 1.86). In general, the coastal region supported high abundance and species richness concerning brachyurans, with high diversity indices, probably because of its more-heterogeneous substrate, which may afford more refuges for certain species. These results suggested that environmental conditions in this area, although they showed certain differences, are favorable for the establishment and development of a diverse brachyuran guild.

Neustonic distribution of decapod planktonic stages and competence of brachyuran megalopae in coastal waters

Settlement rate may not reflect larval supply to coastal waters in different marine invertebrates and demersal fishes. The importance of near-shore oceanography and behaviour of late larval stages may be underestimated. The present study conducted neustonic sampling over station grids and along full-length transects at two embayments in south-eastern Brazil to (1) compare diurnal and nocturnal occurrence of most frequent decapod stages to assess their vertical movements, (2) describe the formation of larval patches and (3) measure competence of crab megalopae according to their distance to recruitment grounds. Several shrimp species apparently undergo a diel vertical migration, swimming crab megalopae showed no vertical movements and megalopae of the intertidal crab Pachygrapsus transversus revealed a reversed vertical migration. During the day, crab megalopae aggregated in convergence zones just below surface slicks. These larvae consisted of advanced, pre-moult stages, at both mid-bay and near-shore patches. Competence, measured as the time to metamorphosis in captivity, was similar between larval patches within each taxon. Yet, subtidal portunids moulted faster to juveniles than intertidal grapsids, possibly because they were closer to settlement grounds. Megalopae of Pachygrapsus from benthic collectors moulted faster than those from bay areas. These results suggest that alternative vertical migration patterns of late megalopae favour onshore transport, and actual competence takes place very close to suitable substrates, where larvae may remain for days before settlement. Lack of correlation between larval supply and settlement for Pachygrapsus suggests that biological processes, besides onshore transport, may play an important role in determining settlement success of coastal crabs.

Biodiversity of brachyuran crabs (Crustacea : Decapoda) from non-consolidated sublittoral bottom on the northern coast of São Paulo State, Brazil

The brachyuran community of the coast of São Paulo State is represented by about 188 species of crabs inhabiting different kinds of coastal marine environments. The biodiversity of brachyurans found on non-consolidated sublittoral bottom was investigated. The Ubatuba region (Ubatumirim, Ubatuba and Mar Virado bays, Couves and Mar Virado Islands, offshore region) was sampled for 3 years (1998-2000), at depths of 2-40 m. All sampling was performed using a fishing boat equipped with two double-rig nets. We collected 79 brachyuran species representing 9 superfamilies (4 Dromioidea, 1 Homoloidea, 2 Calappoidea, 5 Leucosioidea, 20 Majoidea, 7 Parthenopoidea, 17 Portunoidea, 18 Xanthoidea, and 5 Pinnotheroidea) and 41 genera. Ubatuba bay showed the greatest species richness with 50 species, followed by Ubatumirim with 45 and Mar Virado with 29. The number of species collected represents about 57% of the known species of crabs already reported for the shore of São Paulo State. It is worth noticing that this percentage is restricted only to non-consolidated sublittoral bottom. This fact indicates a great biodiversity of the habitat in this studied region, probably one to the diversity of habitat types present in the bays.

Brachyuran community in Ubatuba Bay, northern coast of São Paulo State, Brazil

A bruchyuran crab assemblage from eight transacts at a non-consolidated sublittoral site in Ubatuba Bay was studied on a monthly basis from September 1995 to August 1996. Data about number of individuals of 50 species found and other information such as distribution of the dominant crabs are reported. The family Majidae was represented by 13 species, followed by Xanthidae (13), Portunidae (10), Leucosiidae (5), Calaphidae (2), Dromiidae (2), Parthenopidae (2), Goneplacidae (1), Pinnotharidne (1), and Ocvpodidae (1). The brachyuran taxocoenosis was dominated by Callinectes ornatus (60.4%), Callinectes danae (18.8%), and Hepatus pudibundus (7.7%). representing together 86.9% of the total number of collected brachyurans. The Shannon-Weaver diversity index ranged from 1.10 to 2.06 between transects, and from 1.33 to 2.22 between months, depending more on equitability than on richness.

Bathymetric distribution of brachyuran crab (Crustacea, Decapoda) communities on coastal soft bottoms off southeastern Brazil

The communities of brachyuran crabs living on soft bottoms off Ubatuba in SE Brazil were studied with respect to their structure, bathymetric distribution, composition, diversity and indices of similarity. The data were analyzed using multivariate techniques of classification and ordination. Most of the individuals caught during summer were the swimming crab Portunas spinicarpus at the 35 m isobath, which contributed to the much-decreased diversity in this season and site. Multivariate analysis indicated that the species were distributed according to depth and also in relation to environmental gradients.

BRACHYURAN CRABS (DECAPODA, BRACHYURA) ASSOCIATED WITH THE GREEN SPONGE AMPHIMEDON VIRIDIS (DEMOSPONGIAE) FROM ITAGUA BEACH, SOUTH-EASTERN COAST of BRAZIL

This study provides information on the community structure of brachyuran crabs associated with the green sponge, Amphimedon viridis Duchassaing & Michelotti, 1864, from a beach on the south-eastern coast of Brazil. Monthly collections from May 2002 through August 2003 were carried out on the rocky bottoms off Itagua Beach (23 degrees 27'07 '' S 45 degrees 02'49 '' W). Crabs on the green sponge banks were hand-caught during snorkelling sessions, and 638 crabs belonging to 31 species, 19 genera, and 10 families were obtained. Biological parameters, including sponge volume, number of individuals, density, richness, diversity, evenness, and dominance changed considerably over time. Species recruitment and foraging habit are some of the factors that drive the richness, dominance, and diversity patterns of this community. The green sponge banks are important sites for recruitment, refuge, and feeding of many species of brachyurans. Therefore, they are also important for the conservation of this group on the south-eastern coast of Brazil.

Checklist of the brachyuran crabs (Crustacea: Decapoda) in the rocky subtidal of Vitoria Archipelago, southeast coast of Brazil.

Biodiversity can be useful as an ecosystem indicator for conservation and monitoring, through continuous assessment of its main properties including stability, primary productivity, exploitation tolerance and even global environmental changes. The main purpose of this study was to provide a checklist of the crabs associated with subtidal rocky bottoms at the Vitoria Archipelago, southeastern Brazilian coast. Monthly collections were carried out from February 2004 through January 2006 on three islands at the Vitoria Archipelago (23[degree]44'S-45[degree]01'W). The crabs were hand-caught by SCUBA divers during the daytime, in rock subtidal. A total of 3084 individuals were caught, belonging to 42 species, 28 genera, and 12 families, highlighting Mithraculus forceps (1528) and Stenorhynchus seticornis (407) representing more than 60% of the sample. on the other hand, Dromia erythropus, Moreiradromia antilensis, Ebalia stimpsoni, Garthiope spinipes and Tumidotheres maculatus had only one individual sampled.

Brachyuran and anomuran crabs associated with Schizoporella unicornis (Ectoprocta, Cheilostomata) from southeastern Brazil

The main goals of this investigation were to describe the community structure of anomuran and brachyuran crabs inhabiting reefs constituted by colonies of Schizoporella unicornis, and to provide a species importance ranking for this community. Collections were carried out on S. unicornis reefs at two-month intervals from May 2003 to May 2004, in the rocky sublittoral of the southeastern Brazilian coast. Relative abundance and occurrence were used to rank these species in the hierarchy importance. A total of 2,018 individuals were obtained, in 11 families, 22 genera and 31 species. Porcellanidae and Pilumnidae were the most abundant families, comprising respectively almost 60% and 15% of individuals sampled. The species ranking indicated four main groups A, B, C and D, with group A subdivided. Subgroup A1 contained 9 species, including the species of greatest ecological importance for community regarding abundance and occurrence. The great abundance of crabs associated with S. unicornis seems to be the result of its recognized importance during the crab developmental cycle, and as shelter and food for some Decapod species. These observations reveal the importance of conserving the areas occupied by these reef colonies, which appear to be an important environment for maintaining local biodiversity.