Effects of the organochlorine insecticide lindane (γ-C6H6Cl6) on the population responses of the freshwater amphipod Hyalella azteca

Adult populations of Hyalella azteca, with similar reproductive potential, were exposed in the laboratory to a range of lindane concentrations below the 240-h adult LC50 (26.9 mu g/L) for a period of 35 d. The reproductive status of each population was assessed through quantification of the precopulatory guarding behavior of Hyalella, the number of gravid females, and their brood sizes. At the end of the experiment, recruitment within the H. azteca populations was assessed, and the body lengths of individuals were measured using image analysis. By employing a range of integrated and quantifiable response criteria, the influence of lindane at the individual and at the population level was determined. A lowest observed effect concentration of 13.5 eta g lindane/L was identified. The experimental results are discussed in relation to the reproductive strategies adopted within the treatment groups and with respect to previous toxicity data.