CHEMICAL INDUCTION OF SETTLEMENT IN LARVAE OF THE EASTERN OYSTER <italic>CRASSOSTREA VIRGINICA </italic> (GMELIN)

Abstract

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 <italic>Crassostrea virginica</italic>. In this study, I treated competent <italic>C. virginica</italic> larvae with select chemicals to identify those which are capable of inducing settlement behavior at an average salinity of 9.6 (&plusmn;0.1). The compounds &gamma;-aminobutyric acid and acetylcholine chloride, both at 10<super>-4</super>M, 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<super>-4</super>M, 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 <italic>Crassostrea</italic> genus and may be of value to hatchery personnel or researchers interested in the chemical induction of settlement behavior in the eastern oyster.