TUBERTY, S.R.; MCKENNEY, C.L.; Appalachian State University, Boone, NC; USEPA, Gulf Ecology Division, Gulf Breeze,FL: Ecdysone responses of two estuarine crustaceans exposed through complete larval development to juvenile hormone agonist insecticides

Fenoxycarb and pyriproxyfen are insecticides that gain their toxicity by specifically acting as insect juvenile hormone agonists (JHA), and so are endocrine disruptors by design and effectively prevent larvae from maturing into adults. Efforts to assess the environmental effects of JHAs on nontarget populations of invertebrates have resulted in the utilization of several established estuarine crustacean models. Gravid female grass shrimp (Palaemonetes pugio) and mud crabs (Rhithropanopeus harrisii), species with different developmental plasticity, were collected and held at wet lab conditions (20 ppt salinity, 25 �C) until larval release. Larvae were collected <12hrs after hatch and exposed to JHAs during a static renewal test through end of development in dishes with seawater or nominal concentrations of JHA shown previously to induce significant developmental delays and/or decreased body wts. (ie, 10 �g/L pyriproxyfen; crabs 100 �g/L fenoxycarb, shrimp 50 �g/L fenoxycarb). Samples were collected from stages of development and tested for steroid perturbations as determined by an ecdysone (Ec) competitive enzyme immunoassay (EIA). Larvae were subsampled (10 larvae/sample, n=2 to 8) at each developmental stage, lyophilized, and Ec extracted by homogenization in 80% methanol and elution from C18 cartridges with 25%, 60% and 100% methanol to capture the polar, free, and apolar conjugates, respectively. As was expected a significant difference in survival, delayed development stages, and total time to completion of development was seen in these crustaceans. These physiological endpoints will be linked with perturbations in Ec titers and reported as pg Ec/�g dry wt.