The effect of chemical cues on the settlement of sea cucumber (Apostichopus japonicus) larvae

The effects of four ions and eight neuroactive compounds on inducing larval settlement of A. japonicus were assessed in the present study. All bioassays were conducted in 60 x 9 mm Petri dishes, each contained 10 mL of the test solution and 10 doliolaria larvae. There were significant inductive effects of K+ (10 mmol L-1), NH4 (+) (0.1 mmol L-1), GABA (10(-3)mol L-1), acetylcholine (10(-5)mol L-1), L-DOPA (10(-5)mol L-1), norepinephrine (10(-5)mol L-1) and dopamine (10(-7)mol L-1 and 10(-5) mol L-1) on the settlement of sea cucumber larvae. L-DOPA and dopamine are the most efficient chemical cues to induce A. japonicus larvae to settle. The highest percentage of larval settlement was induced by 10(-5) mol L-1 L-DOPA and dopamine (33% and 40%) compared to the control (7%). However, Ca2+, Mg2+, choline, serotonin, and epinephrine were less effective on larval settlement at all tested concentrations. This study evaluated the stability and feasibility of chemical cues for larval settlement in different culture systems, which can be applied to improve the hatchery production of this valuable species.