Responses of osmotic and chloride concentrations of Penaeus chinensis Osbeck subadults acclimated to different salinity and temperature levels

Abstract

Hemolymph osmolality, chloride concentration and tissue water of Penaeus chinensis Osbeck subadults (16.40 ± 2.82 g) were determined after they were acclimated from 33 ppt to 10, 20, 30 and 40 ppt for 14 days at 24 °C, and then acclimated to 12, 18, 24 and 30 °C for 14 days. Hemolymph osmolality and chloride concentration increased with increased salinity, but decreased with increased temperature. Tissue water decreased with increased salinity. Hemolymph osmolality and chloride concentration were linearly related to medium osmolality and medium chloride concentration, respectively. The isosmotic point and isoionic point was 837, 811, 735, 707 mOsm/kg and 324, 299, 289, 278 mEq Cl−/l which was equivalent to 28.4, 27.5, 25.0, 24.1 ppt and 19.6, 18.1, 17.5, 16.9 ppt for shrimp acclimated to 12, 18, 24, 30 °C, respectively. Hemolymph chloride concentration increased with increased hemolymph osmolality, whereas tissue water decreased with increased hemolymph osmolality. Penaeus chinensis subadults at 24 and 30 °C had superior osmoregulation, and accepted less change of tissue water and hemolymph osmolality than those at 12 and 18 °C due to changes of salinity and temperature.