Résumé
In
Penaeus japonicus, tolerance to copper increased with the developmental stage. In seawater, tolerance was lowest in nauplii (48-h LC
50: 1 μg Cu 1
−1) and zoeae (48-h LC
50: 3–46 μg Cu 1
−1); it increased in postlarvae (96-h LC
50:≈20–1450 μg Cu 1
−1) and was highest in juveniles (96-h LC
50: 2050 μg Cu 1
−1). The 96-h LC
50 of juveniles exposed to dilute seawater was lower (96-h LC
50: 1200 μg Cu 1
−1) than in full-strength seawater. The effect of sublethal concentrations of copper on hypo- and hyper-osmoregulatory capacity in late juveniles was examined in fullstrength seawater (1090 mosm kg
−1, ≈37%.) and in dilute (500 mosm kg
−1, ≈ 17%.), after 6, 12, 24, 48, 96 h, 4 or 7 days. Experimental copper concentrations were 500 (low concentration), 1000 (medium concentration) and 1500 (high concentration) μ Cu 1
−1. Both hypo- and hyperosmoregulation were affected by copper. Hypo-osmoregulatory capacity was significantly reduced after 4 days exposure to low concentration, and it was suppressed after exposure to medium and high concentrations. Hyper-osmoregulatory capacity was significantly reduced after 4 days exposure to low and medium concentrations. The effect of copper on osmoregulatory capacity was time- and dose-dependent. The ability of shrimps to recover hypo-and hyperosmoregulatory capacity was variable. Only the shrimps exposed to low and medium concentrations of copper recovered their hypo-osmoregulatory capacity after 7 days of readaptation in control seawater. In this study, osmoregulatory capacity proved again a sensitive tool to evaluate the physiological condition of shrimp and the adverse effect of copper.