Chemical induction of settlement and metamorphosis in two Babylonia (Gastropoda) larvae

By exposure to 12×10^-3 mol/dm³ K⁺ for 24 h, more than 90% of planktonic larvae of Babylonia formosae and B.areolata were effectively induced to metamorphose completely.15×10^-3mol/dm³ K⁺ exerted toxic effect on larval B.areolata over a 24 h period, but produced better results of induction by 12 h exposure.Metamorphosed juveniles induced by increased by K⁺ could move and feed normally.Percent metamorphosis increased with average shell height for K⁺-induced larvae.L-DOPA, epinephrine and norepinephrine ranging from 5.5×10^-6 to 5.5×10^-5 mol/dm³ had no inductive activity to metamorphosis in larval B.areolata,whereas the rate of metamorphosis induced by dopamine at a concentration of 10^-4 mol/dm³ was approximately half less than that by 12×10^-3 mol/dm³ K⁺.TEA (a K⁺-channel blocker) did not inhibit metamorphosis in the two Babylonia larvae by induction of K⁺.Based on the results of K⁺-induced experiments, it is preliminarily suggested that shell height of larvae achieving metamorphic competence was in the range of 860.2-1 009.8 pm for B.frmosae,and 849.6-956.0 pm for B.areolata.In addition, planktonic larvae of the two Babylonia had delayed metamorphosis.