THE ACUTE TOXICITY OF LINDANE TO HYALELLA-AZTECA AND THE DEVELOPMENT OF A SUBLETHAL BIOASSAY BASED ON PRECOPULATORY GUARDING BEHAVIOR

Acute and sublethal toxicity of the organochlorine insecticide lindane to the amphipod crustacean Hyalella azteca was investigated. Acute ex periments were conducted for a maximum test exposure period of 240 h w ith adult and neonate H. azteca. Median lethal concentrations (LC50s) determined for adult Hyalella included a 48-h LC50 of 47.6 mu g/L and 240-h LC50 of 26.9 mu g/L. For neonate H. azteca 24-, 48-, and 240-h L C50s were 29.5, 14.8, and 9.8 mu g lindane/l, respectively. Neonate H. azteca were approximately three times more sensitive than adults. Two sublethal toxicity bioassays were developed based on the direct and i ndirect disruption of the precopulatory or mate guarding behavior of H yalella. This reproductive behavior is readily quantifiable and of eco logical significance as it is a vital component of the mating success of the species. The direct disruption bioassay examined the separation of precopulatory pairs maintained in control water and a range of lin dane concentrations during a 24-h exposure period. Median separation t imes (ST50s) were determined and the LOEC was 24.4 mu g lindane/l. The indirect disruption bioassay consisted of a test exposure period of j ust 4 h after which an invertebrate anesthetic solution was administer ed to induce separation of precopulatory pairs. The LOEC was 17.3 mu g lindane/l, suggesting that the indirect precopulatory separation bioa ssay was comparable to the 24-h direct separation study. Both bioassay s are rapid, relatively simple to perform, and have yielded effect con centrations that correspond with LC50 values determined using adult an d neonate H, azteca life stages over more prolonged lindane exposures. Following some modification, these behavioral bioassays may be suitab le for use in the hazard evaluation of sediments and for deployment as in situ toxicity tests.