Effects of endosulfan and ethanol on the reproduction of the snail Biomphalaria tenagophila: A multigeneration study

Endosulfan (END) is an insecticide used in agriculture and as a wood preservative. Since END is practically insoluble in water, ethanol (ETOH) is often employed as a carrier solvent to spike it in the test medium in aquatic toxicity assays. In this study were investigated the effects of END and ETOH on the reproduction of the freshwater snail Biomphalaria tenagophila exposed over three successive generations. END (0, 0.001, 0.01, 0.1 mg L−1) was dissolved in the medium water using ETOH (up to 19.8 mg L−1) as carrier solvent. ETOH (19.8, 198, 1980 mg L−1) alone was tested as well. Adult snails (F0-generation) were exposed to END and ETOH for 8 weeks. The F1-generation continued to be exposed from embryo to reproductive maturity, while their descendants (F2) were exposed until day 10 after spawning. Effects on the fecundity (8-week production of eggs and egg-masses) of mature F0 and F1 snails were evaluated. Developmental toxicity was investigated in F1 and F2 embryos. END at the highest level tested (0.1 mg L−1) inhibited egg production by F0 and F1 snails. ETOH at levels ⩾ 198 mg L−1 also reduced fecundity of F0 and F1 an effect that was apparently aggravated by exposure over successive generations. END 0.1 mg L−1 increased mortality and malformations and decreased hatching among F1 embryos. ETOH drastically reduced the proportion of hatchings among F2 embryos. The study-derived NOECs (no-observed-effect-concentrations) for END was 0.01 mg L−1 (reduction in fecundity), and for ETOH were 19.8 mg L−1 for reduction in fecundity and <19.8 mg L−1 for developmental toxicity (hatching retardation).