DAO 60:157-164 (2004)  -  doi:10.3354/dao060157

ABSTRACT: Taiwan abalones Haliotis diversicolor supertexta held in 30‰ seawater and 26°C were injected with tryptic soy broth (TSB)-grown Vibrio parahaemolyticus (1.6 × 10⁵ CFU [colony-forming units] abalone^–1), and then placed in water containing different concentrations of nitrite-N (nitrite as nitrogen): 0.01 mg l^–1 (control), 1.05, 3.04, 5.10 and 10.06 mg l^–1. Mortality of the abalones increased in direct parallel to ambient nitrite-N concentration. Over 12 to 48 h, the mortality of V. parahaemolyticus-injected abalones held in 3.04 mg l^–1 nitrite-N was significantly higher than that of abalones in the control solution. Abalones that had been exposed to control, 0.96, 2.95, 5.03 and 10.16 mg l^–1 nitrite-N for 24, 72 and 120 h were examined for THC (total hemocyte count), phenoloxidase activity, respiratory bursts (release of superoxide anion), phagocytic activity, and clearance efficiency of V. parahaemolyticus. The THC increased in abalone after 72 h exposure to 0.96 and 2.95 mg l^–1 nitrite-N, but decreased in abalones after 24 h exposure to 5.03 and 10.16 mg l^–1 nitrite-N. Phenoloxidase activity and respiratory bursts increased, while phagocytic activity and clearance efficiency decreased in abalones exposed to ≥0.96 mg l^–1 nitrite-N for 24 h. It is concluded that nitrite-N in water at concentrations as low as 0.96 mg l^–1 weakens the immune response and increases mortality of H. diversicolor supertexta infected with V. parahaemolyticus.

KEY WORDS: Haliotis diversicolor supertexta · Vibrio parahaemolyticus · Nitrite · Challenge · Phenoloxidase activity · Respiratory burst · Phagocytic activity · Clearance efficiency