Larval development of Philocheras fasciatus (Risso, 1816) (Decapoda, Caridea) reared in the laboratory, comparison with plankton larvae and occurrence of accelerated development.

Abstract

The complete larval development of Philocheras fasciatus, consisting of four zoeae stages, was obtained in the laboratory at 23 ± 1°C and 33‰ of salinity. The present study provides a description of larval stages that developed in rapid succession. In the genus Philocheras, the normal developmental sequence includes five or more discrete zoeae stages before metamorphosis into a juvenile. In this study, four zoeae stages of P.fasciatus appeared before the juvenile stage. It is possible that complete food requirements, together with a high temperature (8°C above the natural temperature) and low culture density, had induced an irregular accelerated development. In addition, plankton surveys were carried out from January to April 1996 in the coastal waters of Cádiz Bay. A total of 105 specimens were examined and a morphometric comparison was made between the laboratory-reared and planktonic zoeae. The first zoeae obtained in the laboratory did not differ morphologically from those obtained from plankton samples, but they were significantly smaller. Size variations in stages of P.fasciatus seem to be due to culture conditions, and are considered ‘laboratory artefacts’ rather than natural variation in this species.