Short communication Innate immune response of silver catfish (Rhamdia quelen) exposed to atrazine Luiz Carlos Kreutz * , Leonardo José Gil Barcellos, Ezequiel Davi dos Santos, Mateus Pivato, Rafael Zanatta Universidade de Passo Fundo, Faculdade de Agronomia e Medicina Veterinária, Campus I, Bairro São José, BR 282, km 171, 99052-900 Passo Fundo, RS, Brazil article info Article history: Received 25 March 2012 Received in revised form 3 August 2012 Accepted 8 August 2012 Available online 17 August 2012 Keywords: Silver catfish Innate immunity Agrichemical Atrazine abstract The impact of agrichemicals on aquatic vertebrate species has been a matter of increasing concern to researchers and environmentalist. In the present study, we evaluated the effects of a sublethal concentration of atrazine (10% of the LC 50e96h ), a world-wide used herbicide, on the innate immune system of silver catfish (Rhamdia quelen). A significant reduction on phagocytic index, bacteria aggluti- nation and bactericidal activity of the serum, serum lysozyme and total serum peroxidase activity was observed in fish exposed to atrazine for 24 h. After 10 days exposure to atrazine, only bactericidal activity of the serum, bacteria agglutination and total serum peroxidase activity were significantly reduced. Atrazine had no effect on the natural complement hemolytic activity. Our results demonstrate that atrazine decreases the innate immune response of fingerlings, which might increase its susceptibility to opportunistic pathogens. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Atrazine (6-chloro-N 2 -ethyl-N 4 -isopropyl-1,3,5-triazine-2,4- diamine) is a herbicide used world-wide that inhibits the growth of unwanted weeds by interfering with the photosynthesis pathway [1]. In recent years, the persistence and fate of atrazine in soil and water has been a matter of major concern and intensive investigation. The half-life of atrazine in water bodies, soil, and sediments ranges from few weeks to more than 2 years [2]. And, in the environment, by different biochemical processes, atrazine might be degraded into several molecules each with distinct toxicity and persistency [2]. At least one of these molecules, dee- thylatrazine (DEA) is of the most concern and considered almost as toxic as atrazine [2]. Because the presence of residual atrazine in the water might be a treat to a wide range of terrestrial and aquatic animals, the adverse effect of atrazine mainly on aquatic vertebrate species has been a matter of increasing investigation. In South America, atrazine and several other agrichemicals have been found in crop field soil [2e6]. Thus, the effect of such agrichemicals on hematology, biochemistry, hormonal balance, oxidative stress and innate immunity of silver catfish (Rhamdia quelen), a South Amer- ican teleostean fish from the Heptapteridae family, has been the focus of our research [7e12]. In a recent study, we demonstrated that silver catfish fingerlings exposed to atrazine were more susceptible to Aeromonas hydrophila challenge [13]. The deleterious effect of atrazine has also been demonstrated in other fish species. The presence of atrazine in the water caused an increase in serum cortisol and compromised survival capability of Atlantic salmon (Salmo salar) smolts [14], and altered swimming pattern and reduced growth rate of red drum (Sciaenops ocellatus) larvae [15,16]. On Zebrafish (Danio rerio), atrazine increased soluble and microsomal glutathione S-trans- ferase levels [17] and caused delayed organogenesis and functional disturbances of the heart and circulatory system [18]. In Rainbow trout (Oncorhynchus mykiss), atrazine altered hepatic metabolism, estrogenic effect and oxidative stress [19]. However, few studies investigated the effect of atrazine on innate immune response of aquatic species. In freshwater snails (Lymnaea stagnalis) atrazine increased hemocyte concentration but decreased phagocytosis and reactive oxygen species (ROS) production [20]. In frogs (Xenopus laevis and Rana pipiens), an atrazine-containing mixture of herbicides altered the phagocytic activity of X. laevis and the lymphocyte proliferation of R. pipiens [21]. Pacific oyster (Crassostrea gigas) exposed to a mixture of eight pesticides, including atrazine, had a significant reduction on phagocytosis and down regulation of several genes related to hemocyte function [22] and, following challenge with Vibrio splendidus-related pathogenic strains, oyster mortality was signif- icantly increased. Similarly, silver catfish exposed to sublethal concentration of atrazine had reduced number of peritoneal cells and higher susceptibility to challenge with A. hydrophila [11]. Thus, because some of the adverse effects of atrazine are related to immune function and its use continues to increase even in non- agricultural activities, we aimed to investigate whether the innate * Corresponding author. Tel.: þ55 54 33168444; fax: þ55 54 3316 8163. E-mail address: lckreutz@upf.br (L.C. Kreutz). Contents lists available at SciVerse ScienceDirect Fish & Shellfish Immunology journal homepage: www.elsevier.com/locate/fsi 1050-4648/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.fsi.2012.08.006 Fish & Shellfish Immunology 33 (2012) 1055e1059