Microhabitat preferences of Biomphalaria pfeifferi and Lymnaea natalensis in a natural and a man-made habitat in Southeastern Tanzania

Schistosoma mansoni is an important human parasitic disease which is widespread throughout Africa. As Biomphalaria pfeifferi snails act as intermediate host, knowledge of their population ecology is an essential prerequisite towards understanding disease transmission. We conducted a field study and assessed the density and microhabitat preferences of B.pfeifferi in a natural habitat which was a residual pool of a river. Repeated removal collecting revealed a density of 26.6 [95% confidence interval (CI): 24.9-28.3] snails/m2. B.pfeifferi showed microhabitat preferences for shallow water (depths: 0-4cm). They were found most abundantly close to the shoreline (distances: 0-40cm), and preferred either plant detritus or bedrock as substratum. Lymnaea natalensis, a snail which may act as a host for human Fasciola gigantica, also occurred in this habitat with a density of 34.0 (95% CI: 24.7-43.3) snails/m2, and preferred significantly different microhabitats when compared to B.pfeifferi. Microhabitat selection by these snail species was also investigated in a man-made habitat nearby, which consisted of a flat layer of concrete fixed on the riverbed, covered by algae. Here, B.pfeifferi showed no preference for locations close to the shoreline, probably because the habitat had a uniform depth. We conclude that repeated removal collecting in shallow habitats provides reliable estimates of snail densities and that habitat changes through constructions may create favourable microhabitats and contribute to additional disease transmission.

Especiação de metais-traço em sedimentos de florestas de manguezais com Avicennia e Rhizophora

Speciation studies of Fe, Cr, Co, Ni and Cu on reactive fraction (adsorved on oxides, hydroxides, carbonates and clay minerals) and pyrite were performed in Avicennia schaueriana and Rhizophora mangle sediments from Amapá shoreline-Brazil. The soil under Avicennia showed a higher heavy metal concentration in reactive fraction than under Rhizophora. The soil under Rhizophora showed low heavy metal bioavailability, having an increasing association with pyrite across sediment section.

Hidrocarbonetos e esterois como indicadores de fontes e destino de matéria orgânica em sedimentos da Baía de Sepetiba, Rio de Janeiro

The inputs of organic matter derived from natural and anthropogenic sources to Sepetiba Bay were investigated by using aliphatic hydrocarbons and sterols in superficial sediments. Concentrations ranged from 0.26 to 2.65 μg g-1, <0.01 to 17.41 μg g-1 and 0.77 and 9.24 μg g-1 for n-alkanes, UCM (unresolved complex mixture) and total sterols, respectively. The selected markers and ratios among individual compounds showed the major contribution of terrestrial sources to the total pool of sedimentary organic matter in the bay, but the accumulation of autochthonous organic matter increased with distance from the shoreline. The input of petroleum hydrocarbons and sewage (coprostanol in the range 0.01 to 0.43 μg g-1) were also detected, especially in the more urbanized regions of the bay, but at lower levels of contamination when compared to estuaries in other Brazilian coastal regions.

The Genus Herposiphonia (Ceramiales, Rhodophyta) in the Coral Reefs Environmental Protection Area, Northeastern Brazil, with new records for Brazil and the Atlantic Ocean

This paper presents a taxonomic study of taxa of the red algae genus Herposiphonia (Ceramiales) occurring on Maracajaú Reef in the Coral Reefs Environmental Protection Area (CREPA - Área de Proteção Ambiental dos Recifes de Corais) in Rio Grande do Norte State, along the northeastern coast of Brazil. The CREPA comprises coastline and continental shelf areas of the municipalities of Touros, Rio do Fogo, and Maxaranguape and includes sand dunes, coastal lagoons, and the adjacent shoreline and offshore reefs. Detailed morphological studies were made, considering recent taxonomic criteria for species delimitation of Herposiphonia, and five species were identified: H. delicatula, H. nuda, H. parca, H. secunda, and H. tenella, thus increasing the number of species in the genus from three to six. Herposiphonia delicatula and H. parca represent new occurrences for Brazil, and H. nuda is reported for the first time for the Atlantic Ocean.