Environmental Toxicology and Pharmacology 27 (2009) 321–326 Contents lists available at ScienceDirect Environmental Toxicology and Pharmacology journal homepage: www.elsevier.com/locate/etap Paraquat and temperature affect nonspecific immune response of Colossoma macropomum Raquel Salazar-Lugo a,∗ , América Estrella a , Aridays Oliveros a , Evelyn Rojas-Villarroel b , Luz Villalobos de B c , Mairin Lemus d a Laboratorio de Proteínas e Immunotoxicidad, Postgrado de Biología Aplicada, Universidad de Oriente, Núcleo de Sucre, Cumaná, Estado Sucre, Venezuela b Laboratorio de Bioquímica. Facultad de Veterinaria, Universidad del Zulia, Maracaibo, Estado Zulia, Venezuela c Laboratorio de Microbiología, Postgrado de Biología Aplicada, Universidad de Oriente, Núcleo de Sucre, Cumaná, Estado Sucre, Venezuela d Laboratorio de Ecofiosiología y Toxicología Ambiental, Instituto Oceanográfico de Venezuela, Universidad de Oriente, Núcleo de Sucre, Cumaná, Estado Sucre, Venezuela article info Article history: Received 22 September 2008 Received in revised form 18 November 2008 Accepted 22 November 2008 Available online 28 November 2008 Keywords: Colossoma Paraquat Temperature Immune system abstract This study evaluated the effect of paraquat (PQ) and temperature on hematological parameters and nonspecific immune system of fish Colossoma macropomum (Cachama). Juveniles were used for all experi- ments. Fish were exposed to three temperatures (18, 28, 35 ◦ C) and 10 mg/L PQ during 21 days (PQ LC 50 96 h was of 48.05 mg/L). Hematological (Hb, Ht, VCM, HCM and CHCM and RBC) and immunological parameters (WBC, differential count of white cells, phagocytes, and bacterial killing by phagocytes) were analyzed for 7, 14 and 21 days. Fishes PQ exposed at 18 ◦ C decreased Hb, MCH and MCHC; we observed sickle erythrocytes in control group at 18 ◦ C, and in PQ-exposed groups at 18 and 35 ◦ C. Immunological param- eters were not affected by temperature. Neutrophils decreased significantly in all PQ-exposed groups. Bacterial killing by phagocytes decreased in 18 and 35 ◦ C PQ-groups; a synergistic interaction was shown between PQ and temperature on WBC and lymphocytes. These results indicate that PQ affected neu- trophils counts independently of temperature exposure; the temperature exerted a synergistic effect on PQ toxicity in lymphocyte counts and phagocytic response and besides nonspecific immune response, PQ and temperature affects hematological parameters such as Hb, MCH, MCHC and erythrocytes morphology. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Paraquat (PQ, 1-1 ′ dimethyl-4-4 ′ bipiridinium dichloride) is a quaternary herbicide widely used in Venezuela for broadleaf weed control in yucca, maize and other cultures (Báez et al., 1998; Girón and Alfonso, 2000; García and y Mejía, 2005). This herbicide has been known to be a highly toxic compound for humans and ani- mals. Its extensive uses create many problems because of its toxicity for non-target organisms, such as fish. Reports have demonstrated that PQ increase antioxidants enzymes and metallothioneins, and decrease glutathione levels in fish (Parvez and Raisuddin, 2006). Immunotoxicology is a relatively new field of investigation that is being recognized and used by ecotoxicologists involved in the study of chemical exposure (Zelikoff, 1998). The immune system is more sensitive to xenobiotics and reacts more rapidly than other system, even to concentrations less than those necessary to evoke acute systemic toxicity. The majority of the immunotoxicological studies has been made in higher vertebrates, i.e. mammals, and ∗ Corresponding author. Tel.: +58 2934002270; fax: +58 2934002270. E-mail address: raquelugove@yahoo.com (R. Salazar-Lugo). although the xenobiotics always affects the aquatic environment, their possible immunotoxic and biochemical effects on aquatic organisms have received relatively little attention so far (Bols et al., 2001; Galloway and Handy, 2003). The effect of possible persistent exposure to herbicide such as PQ on the integrity of the biological system in fishes has recently drawn interest as an additional indicator of a potential problem. Due to PQ is a redox reagent that generates oxygen free radicals, it is a potential immunotoxicant compound. Additionally, the effect of temperature on the immune response of ectoderms such as teleost is of particular interest, especially as fishes are unable to regulate their internal temperature. Temperature has been found to be the principle environmental cue stimulating changes in the immune response of many different fish species, affecting both innate and acquired immune responses (Bly and Clem, 1992). The “cachama” or “Tambaqui” Colossoma macropomum is one of the most important freshwater neotropical fish for aquacul- ture development in Venezuela; it is widely distributed in South America, very abundant in the river basins of the Amazon and Orinoco rivers, and is very important for the local riverside economy (Machado-Allinson, 1982; Novoa and Ramos, 1982). The cachama could be potential targets of toxicants because it inhabits floodplain lakes and it is an omnivore fish. Furthermore, cachama is a good 1382-6689/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.etap.2008.11.010