Acute toxicity of copper sulphate and potassium chromate to “tailless freshwater flea”, Simocephalus vetulus (Crustacea-Cladocera).

The objective of this study was to evaluate the acute toxicity (LC50) and behavioural alterations by heavy metals, copper sulphate and potassium chromate to “tailless freshwater flea”, Simocephalus vetulus (Crustacea-Cladocera). S. vetulus were subjected to static bioassay tests to ascertain the LC50 values and their 95% confidence limits of copper sulphate and potassium chromate which were calculated according to trimmed Spearman-Karber method. The LC50 values of 24, 48, 72 and 96hr exposure for copper sulphate and potassium chromate to S. vetulus were found to be 0.87, 0.58, 0.45, 0.37 mgL-1 and 0.70, 0.33, 0.23, 0.16 mgL-1 respectively. Behavioural alterations like hyperactivity, fast appendage movements and avoidance were noticed at initial stage and at later stage erratic swimming and spinning, reduced activity were common in both metals while darkening of cuticle in copper and cuticular lightening in chromium were peculiar alterations. LC50 values indicated that S. vetulus were more sensitive to potassium chromate than copper sulphate. The behavioural response and changes of S. vetulus showed the most sensitive indication of potential toxic effects. Hence LC50 values of present study showed to be an important predictive and sensitive biomarker in aquatic monitoring and pollution management.