Résumé
Survival under different salinity temperature combinations has been studied in P20, P40, P60 post-larvae of Penaeus japonicus and P. chinensis. The average LS 50, 96 hours for the three stages are 19.3 parts per thousand at 10 degrees C, 12.1 parts per thousand at 14 degrees C, 6.4 parts per thousand at 18 degrees C, 5.4 parts per thousand at 25 degrees C in Penaeus japonicus and 11.3 parts per thousand at 14 degrees C, 7.2 parts per thousand at 18 degrees C, 11.1 parts per thousand at 25 degrees C in P. chinensis. Low temperature (10-14 degrees C) decreases the tolerance of Penaeus japonicus post-larvae to low salinities; this influence is less important in Penaeus chinensis post-larvae. At all the tested temperatures, mortality is lowest when the medium is isosmotic to hemolymph. Long term survival assays (35 days) have been conducted on post-larvae of the two species. Osmotic regulation of post-larvae and adults of both species is hyper-osmotic in dilute media and hypo-osmotic in seawater and 900mosm.kg(-1) media. In Penaeus japonicus, the osmoregulation curves or P20, P40, P60 post-larvae are similar, but the ability to osmoregulate is lower in adults than in post-larvae. In Penaeus chinensis the ability to regulate in dilute media increases with age in post-larvae, and the adults are better hyper-regulators than P60 post-larvae. In P40 postlarvae of Penaeus japonicus, osmoregulation pattern changes and becomes isosmotic in sea water when animals reared at 18 degrees C are exposed for 8 days at 10 degrees C. The results lead to recommendations regarding optimal conditions of temperature and salinity for post-larval rearing and for their release into tanks or lagoons.