Change in water temperature on the immune response of Taiwan abalone Haliotis diversicolor supertexta and its susceptibility to Vibrio parahaemolyticus

Taiwan abalones, Haliotis diversicolor supertexta, held in 30‰ seawater at 28 °C, were injected with TSB-grown Vibrio parahaemolyticus (1.6×105 cfu abalone−1) and then transferred to 20, 24, 28 and 32 °C. All abalones transferred to 32 °C died by 72 h. The mortality of V. parahaemolyticus-injected abalone held at 20 and 24 °C was significantly lower over 24–96 h, compared to animals held at 28 and 32 °C. In a separate experiment designed to measure immune function, abalones held in 30‰ seawater at 28 °C and then transferred to 20, 24, 28 and 32 °C were examined for total haemocyte count, phenoloxidase activity, respiratory burst, and phagocytic activity to V. parahaemolyticus after 24, 72 and 120 h. The phenoloxidase activity and phagocytic activity decreased significantly, whereas respiratory burst increased significantly in abalone transferred to 32 °C. It is concluded that transfer of abalone from 28 °C to 32 °C reduced their innate immunity and resistance against V. parahaemolyticus infection.