Parasitas em ostras de cultivo (Crassostrea rhizophorae e Crassostrea gigas) da Ponta do Sambaqui, Florianópolis, SC Parasites in cultured oysters (Crassostrea rhizophorae and Crassostrea gigas) from Ponta do Sambaqui, Florianópolis, SC

Estudou-se a presença de parasitas e realizaram-se exames macroscópicos e histológicos em ostras (Crassostrea rhizophorae e Crassostrea gigas) cultivadas. Entre agosto de 2002 a maio de 2003, 30 indivíduos adultos de cada espécie foram coletados sazonalmente, totalizando 240 ostras. Os animais, provenientes de desova em laboratório, foram mantidos em lanternas de cultivo, em sistema suspenso tipo espinhel, com densidade de 40 ostras/andar. A cada coleta era registrada a mortalidade das ostras, a temperatura e a salinidade da água. A temperatura variou de 19 a 28,5°C e a salinidade, 31 a 35‰. A mortalidade foi de 48,3% para C. gigas e 70,8% para C. rhizophorae. A infestação pelo poliqueta Polydora websteri em C. gigas foi 100% durante todo o período e em C. rhizophorae, 100% em fevereiro e maio. O mal do pé foi observado em novembro (3,3%) e maio (23,3%) em C. gigas e maio (6,6%) em C. rhizophorae. As maiores prevalências do protozoário Nematopsis sp. foram de 70 e 60% em C. gigas e C. rhizophorae, respectivamente. O protozoário Trichodina sp. ocorreu em 1,6% de C. rhizophorae, e larvas do cestóide Tylocephalum sp. foram observadas em 2,5% de C. gigas. Nenhum dos parasitas encontrados foi associado à mortalidade das ostras.Over a 10-month period, cultured oysters (Crassostrea rhizophorae and Crassostrea gigas) from Ponta do Sambaqui, Florianopolis, Santa Catarina State were evaluated microscopically and histologically for parasite infection. Thirty mature individuals of each species were examined each season, for a total of 240 oysters. The animals, which originated from laboratory spawning, were kept in culture lanterns suspended in long-line systems at a density of 40 oysters per floor. Mortality, water temperature (19 to 28.5 ºC range) and salinity (31 to 35‰) were recorded at each sampling. The total amount of dead oysters was 58 (48.3%) to C. gigas and 85 (70.8%) to C. rhizophorae. All C. gigas individuals were infected with polydiariosis parasites (100%) throughout the experimental period; whereas 100% infection of G. rhizophorae with polydiariosis was observed only in February and May. "Foot disease" was detected in 3.3% of C. gigas oysters in November and in 23.3% of C. gigas and 6.6% of C. rhizophorae oysters in May. The highest incidences of Nematopsis infection were 70% and 60% in C. gigas and C. rhizophorae, respectively. Trichodina protozoa occurred in 1.6% of G. rhizophorae individuals; while Tylocephalum cestoda larvae were found in 2.5% of C. gigas individuals examined. Total mortality percentages of 48.3 in C. gigas and 70.8 in C. rhizophorae could not be associated with parasite infection

Role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils

Heavy metal pollution of soil is a significant environmental problem and has its negative impact on human health and agriculture. Rhizosphere, as an important interface of soil and plant, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria have received more and more attention. This article paper reviews some recent advances in effect and significance of rhizobacteria in phytoremediation of heavy metal contaminated soils. There is also a need to improve our understanding of the mechanisms involved in the transfer and mobilization of heavy metals by rhizobacteria and to conduct research on the selection of microbial isolates from rhizosphere of plants growing on heavy metal contaminated soils for specific restoration programmes