The effect of chemical cues on settlement of pearl oyster Pinctada fucata martensii (Dunker) larvae

The pearl oyster Pinctada fucata martensii is an important aquaculture species in South China Sea and has great commercial value in the pearl culture industry. As difficulties in the commercial culturing of molluscs are mainly associated with larval settlement and metamorphosis, it is important to find a routine, inexpensive and effective technique for the induction of synchronous settlement and metamorphosis of larvae. In the present study, the effects of 11 chemicals on inducing larval settlement of the P. fucata martensii were investigated in the laboratory. The larvae were exposed to the chemicals for 96 h. Among the chemicals tested, K+ (10 and 20 mm), Ca2+ (1 and 50 mM), gamma-aminobutyric acid (10(-4) M), 3-isobutyl-1-methylxanthine (10(-4) M), choline(10(-3), 10(-4) M), acetylcholine (10(-4) M), and serotonin (10(-3), 10(-4), 10(-5) M) induced high percentage of the larvae to settle without acute toxic effects, while Mg2+, NH4+, dopamine, and 3-(3,4-Dihydroxyphenyl)-L-alanine at all the tested concentrations were less effective. Serotonin of 10(-4) M resulted in the highest settlement rate, but the chemical is expensive. K+ was slightly less effective, but the chemical is much cheaper, therefore maybe more economical in the commercial production. (C) 2008 Elsevier B.V. All rights reserved.