Induction of metamorphosis and its effect on the growth and survival of postmetamorphic juveniles of Chorus giganteus (Gastropoda: Muricidae)
2001
Gallardo, C.S. | Sanchez, K.A.
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.
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