Acute toxicity and bioaccumulation of endosulfan in rotifer (Brachionus calyciflorus)

1. The acute toxicity of endosulfan was determined for the freshwater rotifer Brachionus calyciflorus. 2. The mean 24 hr LC50 value for endosulfan was 5.15 ppm with a coefficient of variation of 14.7%. 3. Rotifers were exposed at two sublethal concentrations (1.5-2.0 ppm) of endosulfan for bioaccumulation experiments, for an exposure time of 24, 48, 72 and 96 hr. The rotifers were fed with Nannochloris oculata (5 x 10(5) cell/ml). 4. The highest accumulation of endosulfan was found 24 hr after the start of the exposure to 1.5 ppm of the toxicant. A steady-state concentration in rotifer was reached between 24-48 hr, followed by a gradual decrease until 96 hr.