Ecological distribution of the shrimp Nematopalaemon schmitti (Crustacea: Decapoda: Caridea) in three bays on the south-eastern coast of Brazil

The relationships between the spatial and temporal variations in the abundance of the shrimp Nematopalaemon schmitti and water temperature, salinity, and texture and organic-matter content of the sediment, were analysed in Ubatumirim, Ubatuba and Mar Virado bays on the northern coast of São Paulo, Brazil. Sampling was carried out monthly, from January 1998 through December 1999, from a shrimp boat equipped with double-rig nets, along six transects in each bay. In total, 2 116 specimens of N. schmitti were caught. Their distribution differed among bays, transects and seasons (ANOVA, p < 0.05). Highest total abundance was found in areas of high organic-matter content, in substrate composed mainly of very fine sand and silt and clay, and during winter and autumn. Although multiple regression analysis showed no significant relationship (p > 0.05), observations suggest that water temperature, sediment texture, organic-matter content, and the presence of biodetritus and plant fragments, provided favourable environmental conditions for the establishment of N. schmitti in the region.

Intra- and extracellular osmotic regulation in the hololimnetic Caridea and Anomura: a phylogenetic perspective on the conquest of fresh water by the decapod Crustacea

We investigate extra- and intracellular osmoregulatory capability in two species of hololimnetic Caridea and Anomura: Macrobrachium brasiliense, a palaemonid shrimp, and Aegla franca, an aeglid anomuran, both restricted to continental waters. We also appraise the sharing of physiological characteristics by the hololimnetic Decapoda, and their origins and role in the conquest of fresh water. Both species survive salinity exposure well. While overall hyperosmoregulatory capability is weak in A. franca and moderate in M. brasiliense, both species strongly hyporegulate hemolymph [Cl-] but not osmolality. Muscle total free amino acids (FAA) increase slowly but markedly in response to the rapid rise in hemolymph osmolality consequent to hyperosmotic challenge: 3.5-fold in A. franca and 1.9-fold in M. brasiliense. Glycine, taurine, arginine, alanine and proline constitute a parts per thousand 85% of muscle FAA pools in fresh water; taurine, arginine, alanine each contribute a parts per thousand 22% in A. franca, while glycine predominates (70%) in M. brasiliense. These FAA also show the greatest increases on salinity challenge. Muscle FAA titers correlate strongly (R = 0.82) with hemolymph osmolalities across the main decapod sub/infraorders, revealing that marine species with high hemolymph osmolalities achieve isosmoticity of the intra- and extracellular fluids partly through elevated intracellular FAA concentrations; freshwater species show low hemolymph osmolalities and exhibit reduced intracellular FAA titers, consistent with isosmoticity at a far lower external osmolality. Given the decapod phylogeny adopted here and their multiple, independent invasions of fresh water, particularly by the Caridea and Anomura, our findings suggest that homoplastic strategies underlie osmotic and ionic homeostasis in the extant freshwater Decapoda.

Aspectos biológicos do peixe-olhudo-dentinho, Synagrops bellus (Actinopterygii: Acropomatidae), da plataforma externa e talude superior do estado de São Paulo, Brasil.

Biological aspects of the blackmouth bass Synagrops bellus from the outer shelf and upper slope along the coast of São Paulo, southeastern Brazil, are presented. The species represented about 71.6% and 9.7% in number of the total catch performed by balloom trawl in the isobaths of 300m and 500m respectively. Body sizes of 266 individuals ranged between 130 and 265mm total length, with sex ratio of 55.9% males, and 44.1% females, where most individuals were in maturation stage. Twenty two food items were found, pointing out Myctophidae fishes, Penaeidea and Caridea shrimps, Brachyuran megalopae, Enoploteuthidae and Cranchiidae cephalopods, pteropods and tunicates. The intestinal coefficient increases as the body size increase, and the number of gill rakers ranged between 16 and 17. Length-weight relationship was WT = 6.0 x 10-6 x TL3.12, r2 = 0.9495. Synagrops bellus is an important link between zooplankton and micronekton, and demersal and pelagic predators in the outer shelf and upper slope in southwestern Brazilian coast.