THE LARVAL DEVELOPMENT OF THE COMMENSAL CRAB POLYONYX GIBBESI Haig, 1956 (CRUSTACEA: DECAPODA)

¹ Institute of Marine Sciences, University of Miami, Miami, Florida 33149

1. The larval development of the porcellanid crab, Polyonyx gibbesi, a commensal with the polychaete worm Chaetopterus variopedatus, is described and illustrated. Two series of larvae were hatched and maintained in the laboratory, one fed with Artemia nauplii and the other starved. Members of each series were held at 10°, 15°, 20°, 25° and 30° C. At 25° C. the fed larvae hatched as prezoeae and molted through two additional zoeal stages to the megalopa. Duration of the pre-zoeal stage is about two hours, each of the zoeal stages usually lasts six to seven days and the megalopa lasts 12-14 days before molting to first crab. No crab stages were obtained above or below 25° C. and no megalopae were obtained below 20° C. Starved larvae died before attaining Stage II.

2. Comparison of the larvae of Polyonyx gibbesi with those of Polyonyx quadriungulatus, an eastern Pacific species, shows the zoeae and megalopae to be almost identical both in appendages and in form, numbers, and placement of setae. Similarity of morphology and habitat plus geographical isolation indicate that P. gibbesi and P. quadriungulatus are geminate species.

3. Larvae of Polyonyx gibbesi possess certain features which allow them to be recognized in the plankton as well as distinguished from known larvae of genera of other western Atlantic porcellanid crabs.