Seasonal variation and comparative analysis of non-specific humoral immune substances in the skin mucus of olive flounder (Paralichthys olivaceus).

The epidermal secretion of fish contains various non-specific immune substances that act as the first line of defense against invading pathogens. The present study investigated the level of mucosal antibodies, the activities of hemagglutinin and protease, and other enzymes in the skin mucus of farm reared olive flounder (Paralichthys olivaceus) for 1 year, in order to gain an insight into the relationship between these mucosal immune substances and their seasonal variation. These levels varied significantly during different months of sample collection. The present study showed a positive correlation between water temperature and the level of mucosal antibodies, and an inverse relationship between the level of mucosal antibodies and the activity of mucosal hemagglutinin and protease, but no relationship between lysozyme activity and other innate immune substances. This relationship is thought to be a compensatory response in olive flounder to protect itself against pathogenic microorganisms which are inherently present in the aquatic environment.