CHEMICAL INDUCTION OF SETTLEMENT IN LARVAE OF THE EASTERN OYSTER <italic>CRASSOSTREA VIRGINICA </italic> (GMELIN)
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Although numerous studies have been conducted to examine the effects of neuroactive compounds on bivalve larvae, few have identified chemicals capable of inducing settlement behavior in the eastern oyster Crassostrea virginica. In this study, I treated competent C. virginica larvae with select chemicals to identify those which are capable of inducing settlement behavior at an average salinity of 9.6 (±0.1). The compounds γ-aminobutyric acid and acetylcholine chloride, both at 10-4M, did not significantly increase the percentage of larvae exhibiting settlement behavior. As compared with the control, a significant increase in settlement behavior was induced by treatment with 3-isobutyl-1-methylxanthine, 5-hydroxytryptamine, and L-3, 4-dihydroxyphenylalanine all at 10-4M, as well as ammonia as a solution of 7.9mM NH4Cl (pH=8.0). These findings differ somewhat from the results of similar studies involving other species in the Crassostrea genus and may be of value to hatchery personnel or researchers interested in the chemical induction of settlement behavior in the eastern oyster.