Seasonal variation in the innate immune parameters of the Asian catfish Clarias batrachus

To determine if the innate immunity of Asian catfish (Clarias batrachits) raised in captivity are affected by the rearing temperature or seasons, various indices of the Immoral and cellular innate immune functions were measured in fish reared at a wide range of water temperatures over a period of 2 years. Measures of Immoral immunity included the estimation of serum mycloperoxidase, lysozyme, haemagglutinin and alternative complement activities. Cellular assay quantified the ability of blood phagocytes to mount superoxide production. Fish were sampled during different periods of two consecutive years, maintained at similar prevailing ranges of water temperature. Experiments were performed at mean temperatures of 19, 24, 28, 31, 32.5 degrees C during the same time of 2 years. The kinetics of the temperature or season mediated immunomodulation in the innate immune parameters was remarkably fluctuated among the individuals and at different periods or temperatures. Although a clear seasonal variation was marked in the innate immune parameters of this species, the fluctuations of all the parameters are not consistent to any of the temperatures except for lysozyme levels that remained significantly lower during summer compared to other seasons. The probable compensatory mechanism among the innate defence molecules might be playing role to protect from infections during different water temperatures or seasons. (c) 2005 Elsevier B.V. All rights reserved.