Induction of metamorphosis
and its effect on the growth and survival of postmetamorphic juveniles of Chorus
giganteus (Gastropoda: Muricidae)
C.S. Gallardo, K.A. Sánchez-2001
Aquaculture,
201(3-4): 241-250
Abstract:
One of the most critical steps in the life cycle of a
mollusc is marked by its abandonment of planktonic life and passage through
metamorphosis to assume a benthonic existence. The present study evaluated
the usefulness of potassium ion (as KCl) to determine competence for
settlement and effectiveness in induction of metamorphosis in free-swimming
larvae of the commercially valuable snail Chorus giganteus. Two
groups of larvae were compared, the first of natural origin, and the second
from egg capsules produced under culture conditions. In both cases,
concentrations of 20 and 30 mM K+ ion effectively induced
metamorphosis of recently hatched larvae of this species, indicating that
they were competent at the moment of release from their egg capsules.
Concentrations of 40 and 50 mM of this ion proved toxic to the larvae.
Observations were made on the relative effects of artificial induction of
metamorphosis on survival and growth in both groups of juvenile snails
during their first 5 months in out-culture. The results showed comparatively
higher survival of individuals from egg capsules produced in the culture
system. Among the artificially induced subgroups of juvenile snails, those
obtained from culture and induced with 30 mM KCl had the highest growth
rate. Among the non-induced subgroups, juveniles from culture had higher
growth rates than those from the field. The results suggested differences
between cohorts of this species with respect to the origin of the egg
capsules, which are interacting with the response of the juveniles to the
different treatments, a factor of some significance to future research and
development of this culture.
(Instituto de Zoología E.F. Kilian, Universidad Austral de Chile, Casilla 567, Valdivia, Chile, e-mail: cgallard@uach.cl)