INFLUENCE OF GROUP DENSITY AND SEX-RATIO ON THE IMMUNE-RESPONSE IN THE TILAPIA OREOCHROMIS-MOSSAMBICUS (PETERS)

We report here the modulatory influence of overcrowding and sex ratio on humoral response to bovine serum albumin in the fish Oreochromis mo ssambicus. Significant enhancement was found in overcrowded groups com pared to the control group and the enhancement was directly proportion al to the degree of overcrowding. When the sex ratio and the group den sity were investigated, it was observed that there were differences in antibody titres among the different sex ratio groups. Except equal se x ratio group, all the groups showed enhancement of immune response as a function of overcrowding compared to the control. No immunomodulati on due to overcrowding was observed in the case of equal sex ratio gro up. These results indicate a possible psychoneuroimmunological basis f or the immunomodulation related to sex ratio and group density.