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

The object of this study was to evaluate the acute toxicity of cadmium in different post-embryonic stages of the penaeid shrimp Penaeus japo nicus (Bate, 1888) and to determine the effect of sublethal cadmium on the osmoregulatory capacity used as an indicator of physiological con dition. Tolerance to cadmium increases with the developmental stage. T he least tolerant stages are the nauplii (48 h LC(50): 124 mu g Cd l(- 1)) and the zoeae (96 h LC(50) similar or equal to 10 to 30 mu g Cd l( -1)). The most tolerant stages are the postlarvae (96 h LC(50): simila r or equal to 200 to 3500 Cd l(-1)) and juveniles (96 h LC(50): 5500 m u g Cd l(-1)). In juvenile shrimp, 2000 mu g Cd l(-1) significantly re duce hypo- and hyper-OC. The effect of cadmium on hypo- and hyper-osmo regulatory capacity illustrates a dose- and time-dependent response. S urviving shrimp recover their hypo-osmoregulatory capacity after 6 d o f readaptation in cadmium-free seawater.