CATECHOLAMINES AND DIHYDROXYPHENYLALANINE IN METAMORPHOSING LARVAE OFTHE NUDIBRANCH PHESTILLA-SIBOGAE BERGH (GASTROPODA, OPISTHOBRANCHIA)

The content of catecholamines and dihydroxyphenylalanine in larvae of the nudibranch Phestilla sibogae was analyzed by high-performance liqu id chromatography with electrochemical detection. Dihydroxyphenylalani ne, norepinephrine and dopamine were identified in larvae of all ages examined (5 through 12 days post-fertilization). Dihydroxyphenylalanin e could be accurately quantified only in larvae of ages 8 through 12 d ays, when its average concentration increased from 0.62 to 6.71 x 10(- 2) pmol mu g protein(-1). Between ages 5 and 12 days dopamine rose fro m 0.081 to 0.616 pmol mu g protein(-1), and norepinephrine from 0.45 t o 2.17 x 10 pmol mu g protein(-1). Dihydroxyphenylalanine, dopamine an d norepinephrine were also measured at different stages of metamorphic progress in 10- to 12-day larvae. Dihydroxyphenylalanine increased by a factor of 2.4 between the onset and completion of metamorphosis, bu t levels of dopamine and norepinephrine remained stable. One millimola r alpha-methyl-DL-m-tyrosine, an inhibitor of catecholamine synthesis, inhibited natural metamorphosis and depleted endogenous norepinephrin e and especially dopamine, respectively, to 75% and 35% of control val ues. The existence of unexpectedly high levels of catecholamines in me tamorphically competent larvae, and the association of catecholamine d epletion with inhibition of metamorphosis, indicate that these compoun ds may participate in the control of gastropod development.