Toxicity of selenium on the freshwater tropical worm, Branchiura sowerbyi beddard, 1892

The toxicity of selenium, in the form of sodium selenite, on freshwater tropical worm, Branchiura sowerbyi Beddard, 1892 (Oligochaeta: Naididae: Rhyacodrilinae) was studied. The LC₅₀ values of selenium at 24, 48, 72 and 96h were recorded as 7.086, 4.128, 3.117 and 2.180 mg/l respectively. The mortality of the worm significantly increased (p<0.05) with increasing concentrations of selenium and time of exposure. The toxicity at different time scale and safe levels of selenium to the worm were estimated, in order to generate base line data that could be used to set up water quality criteria (WQC) for the toxicant. The study further focussed on the growth of B. sowerbyi exposed under chronic dose of the toxicant (5 and 10% LC₅₀). The worm showed significant reduction (p<0.05) in growth, measured in the form of dry weight under the influence of chronic doses of the toxicant. The findings will be useful to assess ecological risk for the worm to selenium toxicity.