The settling and metamorphic responses of the larvae were observed after 72-120h of cultivation in a series of detecting media, namely, artificial seawater designed by adding 3-15 mmol/L K⁺ or decreasing 4.0-48.5 mmol/L Mg²⁺ through ionic substitution. The results were as follow. Attachment and metamorphosis of the larvae were effectively induced by increasing 6-12 mmol/L K⁺ or decreasing 16.0-33.5 mmol/L Mg²⁺ in the artificial seawater. The addition of 6-12 mmol/L K⁺ induced 48% attachment and 50% metamorphosis; these were reduced by 41.6% and 52.1% in response to a decrease of 23 mmol/L in Mg²⁺. At 24h, 48h, 72h and l20h intervals, the attachment and metamorphic rates of the larvae were examined for a joint action of cell membrane K⁺-channel blocker TEA (tetraethhylammonitnn chloride) (5×10^-5 mol/L) and the addition of 9 mmol/L K⁺, or for a combination of anion exchange blocker SITS (4-acetamido-4-isothiocyanostilbene-2,2-disulfonate) (1×10^-5 mol/L), TEA (5×10^-5 mol/L) and a 23 mmol/L Mg²⁺ decrease in the artificial seawater. The results show that the action of increasing K⁺ or decreasing Mg²⁺ in inducing. Those two events is inhibited by the K⁺-channel blocker TEA, whilst the anion exchange blocker SITS has no inhibition, indicating that some K⁺-channels in the cell membrane play an important role on excitable cells sensitive to TEA in the process of attachment and metamorphosis. In addition, a higher attachment rate (43.1%) was achieved as a result of a supplement of 9 mmol/L K⁺ or 12 mmol/L K⁺, suggesting that the experimental methods can be applied to improving the technology of the artificial seed breeding of this species.

The inductive effect of the addition of K⁺ on Perna viridis larvae, which resulted in 48% attachment and 50% metamorphosis in this experiment, was much greater than on Saccastrea commercialis larvae, and K⁺ had no induction on attachment and metamorphosis of Medulis larvae. However, such an effect was significantly lower for Perna viridis larvae than in marine gastropod larvae studied previously elsewhere. Based on these results, compared to marine gastropod larvae, settling and metamorphic responses of marine bivalve larvae have a low sensitivity to the addition of K⁺.