METAMORPHOSIS OF PECTINARIA-KORENI (ANNELIDA, POLYCHAETA) AND RECRUITMENT OF AN ISOLATED POPULATION IN THE ENGLISH-CHANNEL

In the Bay of Seine (English Channel) the polychaete Pectinaria koreni exhibits interannual stability in its abundance, despite its isolated distribution and its bentho-planktonic life cycle. To test the hypoth esis of a high level of recruitment related to high survival rate of t he post-larvae due to metamorphosis in the water column (transformatio n of metatrochophore into aulophore), we undertook a study of the morp hology and the dynamics of the aulophore stage during May and June 198 7. The morphological study showed that aulophore larvae do not possess all the morphological features needed for benthic life on their first contact with the substratum. Fifteen days are needed to complete this development, and during this time the mortality rate is high. The pos sible role of this delayed metamorphosis on the transport of aulophore larvae towards sites favourable to adults is also discussed.