Altered Immunological Parameters in Silver Catfish (rhamdia Quelen) Exposed to Sublethal Concentration of an Atrazine- Based Herbicide Alterações De Parâmetros Imunológicos De Jundiás (rhamdia Quelen) Expostos a Concentrações Subletais De Um Herbicida a Base De Atrazine

Agrichemicals have been extensively used on crop field to control unwanted invasive weed species. The impact of agrichemicals on aquatic vertebrate species has been a matter of increasing concern to researchers and environmentalist. The present study aimed to evaluate the acute effects of sublethal concentrations (10% of the LC50-96h) of an atrazine based herbicide on several immune system parameters of silver catfish (Rhamdia quelen) fingerlings. After 24 h exposure of fingerlings to atrazine, a significant reduction on coelomic cell phagocytic index, serum bacteria agglutination and bactericidal activity was observed, but after 10 days exposure only serum bactericidal and serum agglutination activity were reduced. In contrast, a higher antibody agglutination titer was observed 21 days after fingerlings inoculation with Aeromonas hydrophila and exposure to atrazine compared to inoculated nonexposed fish. The data presented herein demonstrate that atrazine decreases the natural immune response of silver catfish and could contribute to increase fish susceptibility to opportunistic infections. In addition, atrazine might contribute to nonspecific immune stimulation that could lead to immune deregulation or autoimmune diseases. Key-words: atrazine, silver catfish, immune suppression, phagocytosis.