EFFECT OF COPPER ON SURVIVAL AND OSMOREGULATION OF VARIOUS DEVELOPMENTAL STAGES OF THE SHRIMP PENAEUS-JAPONICUS BATE (CRUSTACEA, DECAPODA)

In Penaeus japonicus, tolerance to copper increased with the developme ntal stage. In seawater, tolerance was lowest in nauplii (48-h LC(50): 1 mu g Cu 1(-1)) and zoeae (48-h LC(50): 3-46 mu g Cu 1(-1)); it incr eased in postlarvae (96-h LC(50): approximate to 20-1450 mu g Cu 1(-1) ) and was highest in juveniles (96-h LC(50): 2050 mu g Cu 1(-1)). The 96-h LC(50) of juveniles exposed to dilute seawater was lower (96-h LC (50): 1200 mu g Cu 1(-1)) than in full-strength seawater. The effect o f sublethal concentrations of copper on hypo- and hyper-osmoregulatory capacity in late juveniles was examined in full-strength seawater (10 90 mosm kg(-1), approximate to 37 parts per thousand) and in dilute (5 00 mosm kg(-1), approximate to 17 parts per thousand), after 6, 12, 24 , 48, 96 h, 4 or 7 days. Experimental copper concentrations were 500 ( low concentration), 1000 (medium concentration) and 1500 (high concent ration) mu g Cu 1(-1). Both hypo- and hyper-osmoregulation were affect ed by copper. Hypo-osmoregulatory capacity was significantly reduced a fter 4 days exposure to low concentration, and it was suppressed after exposure to medium and high concentrations. Hyper-osmoregulatory capa city was significantly reduced after 4 days exposure to low and medium concentrations. The effect of copper on osmoregulatory capacity was t ime- and dose-dependent. The ability of shrimps to recover hypo-and hy per-osmoregulatory capacity was variable. Only the shrimps exposed to low and medium concentrations of copper recovered their hypo-osmoregul atory capacity after 7 days of readaptation in control seawater. In th is study, osmoregulatory capacity proved again a sensitive tool to eva luate the physiological condition of shrimp and the adverse effect of copper.