[Standardization of larval development of the sea urchin, Paracentrotus lividus, as tool for the assessment sea water quality].

All stages of development of the sea urchin are of interest in ecotoxicology; the largest number of prior works concerns studies on gametes. Previous studies indicated that the use of sea urchin larvae was difficult because of the need to obtain the parent generations and good quality gametes. Progress in sea urchin culture has allowed one to standardize the method. The proposed technique is based on an evaluation of the number of non-developing fertilized eggs, on the frequency of malformations, and on the length of the larvae at 96 hours, using parents raised under well-controlled conditions. Temperature (18-22 degrees C), salinity (28-34 ppt) and pH (8-8.4) have been fixed to standardize the proposed biological test. Thirty micrograms per litre of copper reduce significantly the length of the larvae and could be used as a positive control. On the other hand, reconstituted sea water permits an optimal development of the larvae and may be used as negative control. A seasonal follow-up of water quality has been achieved to validate the use of this technique in a surveillance network of water quality. The method may be used whatever the salinity, including fresh and brackish waters.