Comparative study of biochemical and nonspecific immunological parameters in two tilapia species (Oreochromis aureus and O-mossambicus)

Oreochromis aureus and O. mossambicus were compared in a preliminary study of differences in levels of blood biochemical and nonspecific immunological parameters before and after exposure to acute stress, which was induced by air exposure for 10 min. Two experiments were conducted. In the first expe riment comparisons were performed after two weeks of acclimation ("base-lin e" level), after stress, and for stress response. The latter was calculated for each fish by subtracting the level after stress exposure from the base -line level. Significant differences (p<0.01) were identified between speci es at the base-line level in total plasma cholesterol and total protein lev els. Glucose concentration was significantly different after stress and in stress response. Significant differences between species were also identifi ed in respiratory burst activity of phagocytes after stress and in cerulopl asmin activity after stress. No significant correlation was identified betw een body weight and each of the parameters tested, indicating that the diff erences detected in immunological parameters were not related to the notabl e size difference between the two groups used in this study. The significan t differences in total cholesterol and protein were confirmed in the second experiment. Significant differences (p<0.05) were also detected in levels of albumin, globulin, lactate dehydrogenase, calcium, total bilirubin and t riglycirides, which were measured by autoanalyzer, and in alpha, beta 2, an d IgM globulins, %beta1 and %IgM, which were separated and measured by agar ose gel electrophoresis. Wide variation was detected within O. aureus in so me of the parameters examined. A larger sample size should be used to learn if the differences are large enough to produce segregating O. aureus famil ies for genetic analysis of those parameters. The differences identified su ggest that hybrid families from the two species can be used to construct a segregating population for genetic analysis of immunological traits and str ess response in tilapia.