No evidence of host specialization in a parasitic pea-crab exploiting two echinoid hosts

The pinnotherid crab Dissodactylus primitivus lives parasitically on 2 burrowingechinoid species, Meoma ventricosa and Plagiobrissus grandis. The fecundity of female crabsvaries between hosts, and is higher when parasitizing P. grandis than M. ventricosa. Moreover, thehosts present great variations in morphology (size and density of spines). These characteristicssuggest the potential to differentiate crabs according to host species. We investigated the genetic(microsatellites) and morphometric (outline analysis) differentiation of this parasitic crab between2 host species at 1 Jamaican site (Western Lagoon, Discovery Bay), and compared it with geographicdifferentiation among 4 sites along the north coast of Jamaica. Greater genetic differencesbetween parasites of the 2 sympatric hosts than between parasites of a single host at different geographiclocations would indicate host differentiation. Genetic analyses (microsatellites) did notdetect spatial differentiation (probably due to local hydrography) or differentiation according tohost species. This lack of host differentiation could be explained by mobility of adult crabsbetween hosts. However, there was weak but significant morphological differentiation betweenfemale crabs from the 2 hosts. This morphological difference may reflect constraints due to hostmorphology.

Biodiversidade de caranguejos Branquiúros (Crustacea, Decapoda) associada a bancos da alga Sargassum cymosum (C. Agardh, 1820) na região da Ubatuba, Litoral Norte Paulista

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Complete mitochondrial genome of the Asian paddle crab Charybdis japonica (Crustacea: Decapoda: Portunidae): gene rearrangement of the marine brachyurans and phylogenetic considerations of the decapods

Given the commercial and ecological importance of the Asian paddle crab, Charybdis japonica, there is a clearly need for genetic and molecular research on this species. Here, we present the complete mitochondrial genome sequence of C. japonica, determined by the long-polymerase chain reaction and primer walking sequencing method. The entire genome is 15,738 bp in length, encoding a standard set of 13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes, plus the putative control region, which is typical for metazoans. The total A+T content of the genome is 69.2%, lower than the other brachyuran crabs except for Callinectes sapidus. The gene order is identical to the published marine brachyurans and differs from the ancestral pancrustacean order by only the position of the tRNA (His) gene. Phylogenetic analyses using the concatenated nucleotide and amino acid sequences of 13 protein-coding genes strongly support the monophyly of Dendrobranchiata and Pleocyemata, which is consistent with the previous taxonomic classification. However, the systematic status of Charybdis within subfamily Thalamitinae of family Portunidae is not supported. C. japonica, as the first species of Charybdis with complete mitochondrial genome available, will provide important information on both genomics and molecular ecology of the group.

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.

Distribution of planktonic decapods with special reference to Acetes from nearshore waters of Bombay

Distribution and seasonal variation of decapod larvae were studied from 8 stations off Versova and Mahim during Nov. 1979 to Dec. 1980. Decapod larvae were encountered throughout the year contributing 7.27% of total zooplankton. Numerically, they were more to Versova (av. 1766/100 m super(3)) than Mahim (av. 970/100 m super(3)). Acetes) spp. were common along both the transects. They were represented by Acetes indicus, A. siibogae and A. erythraeus. The effect of physico-chemical parameters in the occurrence of decapod larvae is discussed.

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.

Warm-water decapods and the trophic amplification of climate in the North Sea

A long-term time series of plankton and benthic records in the North Sea indicates an increase in decapods and a decline in their prey species that include bivalves and flatfish recruits. Here, we show that in the southern North Sea the proportion of decapods to bivalves doubled following a temperature-driven, abrupt ecosystem shift during the 1980s. Analysis of decapod larvae in the plankton reveals a greater presence and spatial extent of warm-water species where the increase in decapods is greatest. These changes paralleled the arrival of new species such as the warm-water swimming crab Polybius henslowii now found in the southern North Sea. We suggest that climate-induced changes among North Sea decapods have played an important role in the trophic amplification of a climate signal and in the development of the new North Sea dynamic regime.

Embryonic and larval ecology and biochemistry of offshore decapods

Understanding the biology of offshore species is hardened by the difficulties of sampling in the deep-sea environment. Additionally, due to the vastness of the open ocean, knowledge of early life histories of pelagic larvae is still relatively scarce. In decapod species with bentho-pelagic lifestyle, the transition from life in the seafloor to the water column not only is associated with drastic morphological metamorphosis, but also with changes in behavior and feeding ecology. The purpose of the present thesis was to investigate physiological, biochemical and behavioral adaptation occurring during early development of such species. The Norway lobster, Nephrops norvegicus, and the crab Monodaeus couchi were used as a model as these two species are encountered off the NE Atlantic shelf at depth greater than 300 m. Chapter 1 introduces the challenges faced by both adult and larvae inhabiting such remote habitats, including the effect of food availability on development and oceanographic processes on dispersal and recruitment. The thesis follows early life histories, starting with within-brood variability in the fatty acid (FA) profile displayed by developing N. norvegicus embryos. There were no differences in the FA composition of embryos sampled from both sides of the brooding chamber in most females. However, all females exhibited significant differences in the FA profiles of embryos sampled from different pleopods. Potential causes for the variations recorded may be differential female investment during oocyte production or shifts in FA catabolism during the incubation period promoted by embryo’s location within the brooding chamber. Next, feeding rates and digestive enzymes activity of the early stage larvae was investigated in N. norvegicus. Both stages were able to maximize food intake when larvae were scarce and showed increased feeding rate following periods of starvation. Amylase activity indicated that carbohydrates are not the primary energy reserve and that feeding may be required soon after hatching to trigger amylase activity. Protease activity indicated that protein reserves are catabolized under starvation. These results indicate that larvae may maximize prey ingestion in the presence of plankton patches with higher food abundance and minimize the deleterious effects induced by previous periods of intermittent starvation or unsuitable prey densities/types. Additionally, changes in enzymatic activity may allow newly hatched N. norvegicus larvae to metabolize protein reserves to overcome short-term starvation. Vertical migration behavior and the influence of oceanographic properties were studied next. All zoeal stages of M. couchi displayed reverse diel vertical migration. Abundance of early stages was correlated with chlorophyll a levels. An ontogenic shift in vertical distribution explained the results; earlier zoeal stages remain in the food-rich upper water column while later stages migrate to the bottom for settlement. This vertical migration behavior is likely to affect horizontal distribution of larvae. Indeed, global current patterns will result in low inter-annual variations in decapod larvae recruitment, but short term variations such as upwelling events will cause deviation from the expected dispersal pattern. Throughout development, from the embryo to metamorphosis into benthic juvenile, offshore decapods face many challenges. For the developing individual survivorship will depend heavily on food availability but also on the reserves passed on by the mother. Even though vertical migration behavior can allow the larvae to take advantage of depth varying currents for transport, the effect of general circulation pattern will superimpose local current and influence feeding conditions and affect dispersal and recruitment.

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.