Estudos ecotoxicológicos com Hydra viridissima (Cnidaria: Hydrozoa) / Ecotoxicology studies with Hydra viridissima (Cnidaria: Hydrozoa)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Hydras are the main freshwater representatives of phylum Cnidaria, and when exposed to toxic substances they can display gradual changes in the body structure, whose expression allows determining the lethal and sub-lethal doses of a toxic substance. In the present study, the native species Hydra viridissima was cultured in the laboratory in order to determine its population and individual growth, the time of duplication of the population and its generation time. This species was also submitted to acute toxicity tests with the reference substances potassium dichromate and sodium sulfide, and also to toxicity tests with samples of water and/or sediment of reservoirs of the state of São Paulo, aiming to use this species as organism-test for ecotoxicological studies. The main results were an individual growth rate (k) of 0.43; the maximum length of the hydra column was 2.53 mm and the generation time averaged 6.6 + OU - 1.5 days. This species presented an intrinsic rate of population growth (r) of 0.0468 for the adjusted curve and a time of duplication of the population of 14.8 + OU - 2.63 days. H. viridissima has a sensitivity range for potassium dichromate varying between 2.8 mg/L and 4.3 mg/L, with a mean value of 3.55 mg/L. This species is more sensible to this substance than other species widely used in toxicity tests, including Hydra attenuata. The sensitivity range of H. viridissima to sodium sulfide varies between 17.76 mg/L and 26.08 mg/L, with a LC IND.50 -96h of 21.92 mg/L. A reduction or loss of toxicity to this substance was observed during the test accomplishment. The water and sediment samples of Lobo, Barra Bonita and Promissão reservoirs were not toxic, nevertheless the sediment of Rasgão reservoir was toxic to the hydras. It was concluded that H. viridissima is easy to culture in the laboratory, has a good performance in the culture conditions tested and suffers gradual morphological changes under toxic conditions, being, therefore, a potential test-organism for ecotoxicological studies

ASSUNTO(S)

hydra viridissima ecotoxicology hydra viridissima poluição de reservatórios ciclo de vida reservoir pollution ecotoxicologia life cycle

ACESSO AO ARTIGO

Documentos Relacionados