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COMPARATIVE EMBRYONIC AND LARVAL DEVELOPMENTAL RESPONSES OF THE ESTUARINE GRASS SHRIMP (PALAEMONETES PUGIO) TO THE JUVENILE HORMONE AGONIST FENOXYCARB
Citation:
Tuberty, S. R., C L. McKenney Jr., G M. Cripe, AND M D. Hoglund. COMPARATIVE EMBRYONIC AND LARVAL DEVELOPMENTAL RESPONSES OF THE ESTUARINE GRASS SHRIMP (PALAEMONETES PUGIO) TO THE JUVENILE HORMONE AGONIST FENOXYCARB. Presented at Atlantic Coast Contaminants Workshop, "Endocrine Disruptors in the Marine Environment: Impacts on Marine Wildlife and Human Health", The Jackson Laboratory, Bar Harbor, ME, 22-25 June 2000.
Description:
This work was undertaken in order to develop a sensitive bioassay which indicates adverse effects of estuarine-applied insecticides on nontarget species. Newly developed 'third generation' insecticides are designed to act as hormone agonists and bind to endogenous insect hormone receptors. Control of the insect pest is accomplished by introducing high concentrations of artificial hormones at specific developmental periods, resulting in death or incomplete development. Crustaceans are closely related phylogenetically to insects and have been shown to share hormones responsible for molting, development, and reproduction. Crustaceans, therefore, are likely sentinels for the presence of endocrine disrupting chemicals in estuarine environments. Shrimp were reared separately through both complete embryonic and larval development during static renewal exposure to fenoxycarb, an insect juvenile hormone analogue, at normal concentrations of 1.0 to 1000 ?g/L delivered in acetone. Radioimmunoassay (RIA) was used to determine ecdysteroid (molting hormone) titers of whole larvae and postlarvae following mass culture flow-through exposure to fenoxycarb concentrations of 1, 5, 10 and 50 ?g/L. Polyclonal antibody previously raised against insect ecdysteroids was used in the RIA. Exposures were conducted at 25?1?C, 20?2 o/oo salinity, and a 12 hour light-dark cycle. Fenoxycarb concentration of 1000 ?g/L significantly (p<0.05) inhibited embryonic development to larval hatching, while concentrations <720 ?g/L had no significant (p>0.05) effect on complete embryonic development when compared to controls. Significantly fewer shrimp successfully metamorphosed to postlarvae while exposed through complete larval development to fenoxycarb concentrations >10 ?g/L. Development beyond third zoeal stage was significantly inhibited at fenoxycarb concentrations >183 ?g/L, while development beyond fourth zoeal stage was inhibited by >45 ?g/L. Ecdysteroid titers of day 7 and 14 larvae were not sig