Acetylcholine and serotonin
induce larval metamorphosis of the Japanese short-neck clam Ruditapes
philippinarum
P.M.
Urrutia, K. Okamoto, N. Fusetani-2004
Journal
of Shellfish Research, 23(1): 93-100 (from
ISI Current Contents)
Abstract:
The effects of neuroactive compounds on larval metamorphosis of the Japanese
short-neck clam Ruditapes philippinarum (Heterodonta, Veneridae) were
investigated by exposing pediveligers to acetylcholine, serotonin,
epinephrine, norepinephrine, dopamine, L-3.4-dihydroxyphenylalanine
(L-DOPA), carbamylcholine, and succinylcholine at concentrations of 1, 10,
and 100 muM. Larval metamorphosis with 100 muM serotonin was 80.7%, and that
with 10 muM and 100 muM acetylcholine was 92.9% and 70.6%, respectively. No
significant differences were observed in the induction activities of
epinephrine (35.1-36.1%), L-norepinephrine (2.1-20.3%). L-DOPA (6.4-15.8%),
and nontreated groups (0-5.6%). Dopamine showed no inducing activity.
Treatment with 100 muM carbamylcholine induced 37.6% of metamorphosis in
23-day-old larvae. Larval metamorphosis rate increased significantly with
exposure time when treated with acetylcholine, carbamylcholine, and
serotonin. Low postlarval survivorship after treatments might not be related
to toxicity of chemicals but due to an energy deficiency after an
accelerated completion of metamorphosis in neurochemically stimulated
larvae. The effectiveness of inducer drugs was observed to be age-dependent.
Nineteen-day-old larvae reacted less than 23-day-old ones from the same
cohort. Larvae of R. philippinarum responded differently to
neurotransmitters front bivalves of the subclass Pterimorphia (i.e.,
Ostreidae, Pectinidae, Mytilidae) which are more sensitive to catecholamines
and L-DOPA. This difference suggest that the mechanisms triggering
metamorphosis may differ among bivalve groups.
(Univ. Tokyo, Dept. Aquat. Biosci Lab. Aquat. Nat.
Prod. Chem. Bunkyo KU, Tokyo 1138657, Japan, e-mail of N. Fusetani: anobu@mail.ecc.u-tokyo.ac.jp)