Strain differences in non-specific immunity of tilapia Oreochromis niloticus following challenge with Vibrio parahaemolyticus

Red and black strains of tllap~a Oreochromis nllobcus were compared for d~fferences in non-specific I nmunity Communally reared nalve f ~s h were challenged w ~t h the bacterium Vibno parahaemolyticus Serum lysozyme.phagocyte act~vity and dlfferent~al leucocyte numbers were exanuned In pre-challenge and post-challenge flsh The percent cumulabve mortal~ty In the 2 stralns were not s ~g n ~f lcantly different There was a s i g n ~f ~c a n t effect of straln on serum lysozyme achvlty and phagocyte activ~ty Phagocyte actlvity Increased sign~f~cantly following the d ~s e a s e challenge Lymphocyte numbers decreased significantly in the post-challenge sample, while thrombocytes, neutrophils, and monocytes remained unchanged Thls study prov~des the first report of straln d~fferences in non-specific immunity In tilapla KEY WORDS: Tilapia .