Reproduction and survival
of Daphnia magna Straus, 1820
TERRA1, N.R & FEIDEN2 , I.R.
1 Fundação Estadual de Proteção Ambiental Henrique Luís Roessler, RS – Divisão de Biologia Rua Salvador França, 1707, CEP: 90690 000, Porto Alegre, R S, Brasil. E.mail narart@fepam.rs.gov.br
2 Bolsista CIAMB/PADCT/FINEP/FEPAM Convênio n077971116.00.
ABSTRACT: In the state of Rio Grande do Sul, southern Brazil, trials are performed using Daphnia magna Straus, 1820, to evaluate the environmental quality of river basins in the state and industrial effluents in the area. Since this species is native to regions where water is hard, while the rivers in this region have soft water, it became necessary to develop a test to evaluate the existence or not of stress in this species, due to changes in hardness. This paper presents the results of chronic tests with Daphnia magna Straus, 1820, exposed for 21 days to 10, 40, 80, 120, 160, 200 and 250 mgCaCO3/L. During the period in which the organisms were exposed, observations were performed on alternate days to evaluate the survival and reproduction of individuals, considering water hardness variations. The results obtained indicate that there is no significant difference in the reproduction of D.magna between the least and most water hardness,as used in the assay. Survival at different harnesses was always within the percentage required for control, and thus considered normal.
Key-words: Daphnia magna, hardness, bioassay, Cladocera.