Toxic anorexia as a sensitive endpoint in Daphnia magna

Abstract

The feeding behavior of the cladocera Daphnia magna was studied when subjected to a short‐term exposure to the acaricide tetradifon (4‐chlorophenyl 2,4,5‐trichlorophenyl sulfone). Test species were exposed to sublethal levels of tetradifon and the effect of the toxicant on filtration and ingestion rates was determined. The experiments were performed using the unicellular algae Nannochloris oculata in a density of 5×10⁵ cells/mL as food for the organisms. Rates of filtration and ingestion of D. magna declinedwith increasing toxicant concentrations. The effective tetradifon concentrations in D. magna at which feeding rate were reduced to 50% of that in controls (EC50) were 0.02 and 0.24 mg/L for filtration and ingestion rates respectively.

Key words:

• Tetradifon
• feeding
• toxic anorexia
• Daphniamagna.