Immunological assessment of hybrid striped bass at three culture temperatures

Hybrid striped bass (Morone saxatilisWalbaum×Morone chrysopsRafinesque) were maintained at three water temperatures (23°C, 26°C and 29°C) within their preferred temperature range. Physiological and immunological parameters were measured in each temperature group to determine if an optimal culture temperature exists for various immune functions. No differences were found in the mean haematocrit, leukocrit, and serum cortisol of the three temperature groups; however, changes in the relative numbers of leukocytes in the highest temperature group were suggestive of thermal stress. Nonspecific immunity as evaluated by granulocyte respiratory burst activity and serum spontaneous haemolytic activity was found to be temperature sensitive with the highest responses occurring in the 26°C group. Following immunization with trinitrophenyl-lipopolysaccharide antigen, the passive haemagglutinating antibody response was very rapid (3 days) at 29°C but was delayed (6 days) in the 23°C group, and lower numbers of plaque-forming cells were evident at 7 days post-immunization in the 29°C group reflecting possible faster kinetics. The secondaryin vitroplaque forming cell response to trinitrophenyl-keyhole limpet haemocyanin was also decreased in the highest temperature group indicating fewer memory cells or suppression of the 29°C acclimated cells when stimulated at 23°Cin vitro.