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PHYSIOLOGICAL DYSFUNCTION IN ESTUARINE MYSIDS AND LARVAL DECAPODS WITH CHRONIC PESTICIDE EXPOSURE
Citation:
McKenney Jr., C L. PHYSIOLOGICAL DYSFUNCTION IN ESTUARINE MYSIDS AND LARVAL DECAPODS WITH CHRONIC PESTICIDE EXPOSURE. Presented at Presented at the 22nd Annual Aquatic Toxicity Workshop, Environment Canada, St Andrews, NB, CANADA, October 01 - 05, 1995.
Impact/Purpose:
Presentation
Description:
A variety of physiological functions was examined in an estuarine mysid (Mysidopsis bahia) during life-cycle exposures to four classes of pesticides. Pesticide exposure initially elevated respiration rates of juveniles. These increased metabolic requirements reduced the amount of assimilated energy available for production of new tissue, as reflected in retarded juvenile growth rates and lower net growth efficiencies (K2 values). Reduced young production with sublethal pesticide exposure was accompanied by metabolic alterations. O:N ratios of maturing juveniles indicated shifts from lipids as the primary energy source to increased usage of proteinaceous substrates. Higher O:N ratios during maturation of pesticide-exposed mysids suggest greater reliance on the more energy-rich lipid substrates to support increased metabolic demands, resulting in less lipid being available for reproductive preparations. Laboratory studies have demonstrated that a new type of pesticide, insect growth regulators, adversely impacts larval development of several estuarine crustaceans. Exposure to methoprene, an insect juvenile hormone analogue, inhibited metamorphosis through complete larval development in the mud crab (Rhithropanopeus harrisii) and in the grass shrimp (Palaemonetes pugio) at concentrations similar to those used in mosquito control. Developmental rates of crab zoeae were retarded by methoprene exposure, while crab megalopae and shrimp larvae were unaffected. Methoprene retarded growth rates of larval shrimp concurrent with elevated respiration rates and lower net growth efficiency values. Modifications in O:N ratios of premetamorphic larvae and postlarvae suggest that methoprene altered substrate utilization patterns during metamorphosis in a manner characteristic of those responses by insects to juvenile hormone.