Epinephrine and 1-DOPA promote larval settlement and metamorphosis of the tropical oyster, Crassostrea iredalei (Faustino, 1932): An oyster hatchery perspective

The critical and foundation stage of most invertebrates is during the larval settlement and metamorphosis period. Neuroactive compounds at different levels of concentration and exposure time are frequently used as an inducer in the settlement of most bivalve larvae. The larval settlement of the tropical oyster Crassostrea iredalei was investigated by exposing competent larvae to epinephrine (EPI) and L-3,4-dihydroxyphenylalanine (L-DOPA) at five different concentrations (10(-3), 10(-4), 10(-5), 10(-6) and 10(-7) M) for 1 and 24 h. The control group consisted of the larvae exposed to 1 mu m filtered seawater. The optimum yield, 60% of cemented spat, was recorded when larvae were exposed to 10(-6) M EPI for 1 and 24 h. Larvae exposed to all concentrations of L-DOPA yielded lower percentages of cemented spats (<50%) compared to the larvae exposed to EPI. In this study, it was shown that the use of EPI effectively induced cemented spats compared to L-DOPA. After the larvae had cemented onto the substrate, the larvae started to metamorphose. A delay in the larvae settlement caused the mortality of some larvae. The results showed significant differences (p<0.05) between the control and the treatment groups and they provide useful information on the technique of seed production in hatcheries where the chemicals are able to promote the larval settlement and metamorphosis of the larvae of C. iredalei. (C) 2012 Elsevier B.V. All rights reserved.