HORST,, M. N.*; WALKER,, A.N.; WILSON,, T.G.; BUSH,, P.; CHANG,, E.; MILLER,, T.; VOGEL,, R.; Mercer University ; Mercer University ; Ohio State University; University of Georgia; University of California, Davis; University of Maine; Mercer University ; : Acute Effects of Methoprene on Survival, Cuticular Morphogenesis and Shell Biosynthesis in the American Lobster, Homarus americanus

The acute effects of methoprene on various life stages of the lobster are being investigated in five areas: bioaccumulation, exposure/survival studies, cytopathology/TEM studies, metabolic incorporation studies and SDS-PAGE analysis. After exposure of adult intermolt lobsters to field level concentrations of methoprene (25 ppb/ 24 h), tissue levels of methoprene were determined by GC-MS. The highest accumulation of methoprene was observed in epithelium, gonads and hepatopancreas (6.17 to 3.97 ppm), up to 250-fold concentration of the pesticide.seawater. We find that adult intermolt lobsters bioaccumulate methoprene in specific tissues. Metabolic studies involved exposure of intermolt juvenile lobsters to 10 ppb methoprene (18 h), injection with 35S Translabel, and incubation for 24 h. We observed 90% reduction in the hepatopancreas, 50% reduction in gills, and no effect in muscle. Thus, methoprene causes tissue specific decrease in protein synthesis in juvenile lobsters. The 72 h LC50 for methoprene was 2 ppb in stage II larvae. In vitro metabolic studies with 35S Translabel indicate that even at very low levels, methoprene may cause a block in the exocytosis and/or crosslinking of 3H GlcN labeled precursors into the nacent cuticle. We have analyzed fractions solubilized from control and methoprene treated shell by SDS-PAGE. The gels have then been examined by total protein staining and by Western blots probed with tomato lectin, or antibodies to stress proteins (HSPs). Our results indicate that methoprene alters the synthesis, secretion and/or incorporation of chitoproteins and HSPs in the postmolt lobster.