PLANKTONIC LARVAE OF POLYCHAETES IN THE GULF OF CALIFORNIA, MEXICO
Fernandez-Alamo, M. A.1 & Bhaud, M.2
1 Laboratorio de Invertebrados, Facultad de Ciencias. Universidad Nacional Autonoma de Mexico. A.P. 70-371, Mexico D. F. 04510
2 Observatoire Océanologique de Banyuls, University P. and M. Curie-CNRS, BP 44, 66651 Banyuls-sur-mer Cedex, France
Larvae of polychaetes were sorted from a collection of 116 zooplankton samples taken in 76 localities during the cruise GOLCA 8404 in March-April, 1984. Two families, the Chaetopteridae and Spionidae, are presently the subject of investigation. For the Chaetopteridae, and specifically the genus Spiochaetopterus, the morphology of the collected larvae resembles those of recently erected species from the Pacific. From local observation of adults and larvae, however, it appears that S. costarum is not present in the Gulf of California, and a species with widespread distribution throughout the world progressively disappears, in spite of having a long planktonic larval development. From the Spionidae, in Chaetosphaera, the large sized larvae collected and examined during this survey raise questions concerning the acquisition of competence in old but still planktonic stages. Competence in many species of polychaete does not appear to precede directly the morphological transformation associated with metamorphosis and the transition to the benthonic form.