Research Product

Larval survival, growth, and energy metabolism of an estuarine shrimp (Palaemonetes pugio) were altered by exposure to low ug/l concentrations of an insect growth regulator (the juvenile hormone analogue, methoprene ). Larvae were several orders of magnitude more sensitive to methoprene in a flow-through exposure system than in a static-renewal exposure system. The first two larval stages and the final premetamorphic larval stage were more sensitive to methoprene toxicity than the intermediate larval stages. As indicated by reduced net growth efficiency values, elevated metabolic maintenance demands of exposed larvae were related to retarded larval growth rates. A premetamorphic shift in substrate utilization patterns, thought to be a physiological prerequisite for successful metamorphosis in marine crustaceans, was altered by exposure to methoprene concentrations that prevented completion of larval development through metamorphosis. These findings support an analogous functional approach in the selection of an appropriate testing procedure to evaluate potential environmental hazards of a new type of pesticide. The results of these studies suggest that the use of similar crustacean larval testing procedures would be appropriate in such assessments of insect growth regulators in the marine environment.