Catecholamines in larvae and juveniles of the prosobranch gastropod, Crepidula fornicata

We investigated roles of catecholamines in metamorphosis of the prosobranch gastropod, Crepidula fornicata. Levels of DOPA, norepinephrine (NE) and dopamine (DA) were measured by high-pressure liquid chromatography (HPLC) in competent larvae and juvenile siblings that metamorphosed in response to the natural adult-derived cue or to elevated K⁺. Competent larvae contained 1.58±0.26 (S.E.M.)×10⁻² pmol DOPA, 0.91±0.45×10⁻² pmol NE, and 0.290±0.087 pmol DA (mean values per μg total protein, n=4 batches of larvae). Levels of DA per individual were not different between larvae and juvenile siblings; levels of NE were higher in juveniles. The tyrosine hydroxylase (TH) inhibitor α-methyl-dl-m-tyrosine (α-MMT) depleted DOPA and DA to approximately half of control values without affecting levels of NE. Depletion of DOPA and DA was accompanied by inhibition of metamorphosis in response to the natural cue but not to elevated K⁺. The dopamine-β-hydroxylase inhibitor diethyldithiocarbamate (DDTC) induced high frequencies of metamorphosis at concentrations of 0.1–10 μM. In juveniles induced by 10 μM DDTC, levels of both NE and DA averaged ∼80% of those in control larvae. Catecholamines may function as endogenous regulators of metamorphosis in C. fornicata.