Comparative effects of UVA and UVB irradiation on the immune system of fish

Aquatic organisms can be harmed by the current levels of solar ultraviolet radiation. We have recently shown that exposure of fish to UVB irradiation alters the functioning of the fish immune system, but the effects of WA radiation are unknown. The present study continues this work by characterizing WA irradiation-induced immunological changes in fish. Roach, a cyprinid fish, were exposed to a single dose of either WA (3.6 J/cm(2)) or UVB (0.5 J/cm(2)) irradiation. Both irradiations suppressed transiently mitogen-stimulated proliferation of blood lymphocytes. UVA, but not UVB, decreased hematocrit, plasma protein, and plasma immunoglobulin levels and increased the proportions of blood cells classified as unidentified leukocytes, possibly consisting of UVA-damaged lymphocytes. UVB, but not UVA, altered the functioning of head kidney and blood phagocytes, induced granulocytosis and lymphocytopenia in the blood and increased plasma cortisol concentration. These results imply that both WA and UVB are potent modulators of the immune defence of fish. (C) 2000 Elsevier Science S.A. All rights reserved.