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The lethal concentration of 50% (LC (I) 50-96h) and the histopathologic effects of diquat herbicide on Nile tilapia (Oreochromis niloticus) fish were evaluated in three experiments. The fishes were exposed to concentrations of 0, 25, 30, 35, 40, 45, 50, 55 and 60 mg diquat L-1, and gill and liver histology were evaluated in the surviving fishes. The estimated LC (I) (50-96h) of diquat was 37.28 mg L-1, with lower limits of 33.12 mg L-1 and upper limits of 41.44 mg L-1. In the treatment with 30, 35 and 40 mg L-1, signs of apical fusion of the secondary lamellae were observed; with 45 and 50 mg L-1, congestion of the primary lamellae was observed; in the treatment with 55 mg L-1, congestion of blood vessels on secondary lamellae took place. The livers of fishes in treatments with 0, 25, 30 and 35 mg L-1 showed cordonal organization of hepatocytes. In the treatments with 40 and 45 mg L-1, hypertrophy of hepatocytes took place; with 50 and 55 mg L-1, cell fusion and the presence of vacuoles inside hepatocytes were observed. Diquat presented low risk of toxicity for Nile tilapia, as the more severe histopathologic alterations occurred only in higher concentrations A concentração letal 50% e os efeitos histopatológicos do herbicida diquat para a tilápia nilótica (Oreochromis niloticus) foram avaliados em três experimentos. Os peixes foram expostos às concentrações de 0; 25; 30; 35; 40; 45; 50; 55; e 60 mg de diquat L-1 e a histologia da brânquia e do fígado foi avaliada nos peixes sobreviventes. A CL (I) 50-96h do diquat estimada foi de 37,28 mg L-1, com limite inferior de 33,12 mg L-1 e superior de 41,44 mg L-1. No tratamento com 30, 35 e 40 mg L-1, ocorreram início de fusão apical das lamelas secundárias; com 45 e 50 mg L-1 ocorreram congestão nas lamelas primárias e no tratamento com 55 mg L-1, ocorreu congestão sangüínea nas lamelas secundárias. O fígado dos peixes dos tratamentos controle, 30 e 35 mg L-1 estavam com organização cordonal dos hepatócitos. Nos tratamentos com 40 e 45 mg L-1, ocorreram hipertrofia dos hepatócitos; com 50 e 55 mg L-1 ocorreram fusão celular e presença de vacúolos. O diquat apresentou baixo risco de intoxicação à tilápia nilótica e as alterações histopatológicas mais severas ocorreram somente nas concentrações mais elevadas

Made available in DSpace on 2013-08-12T17:56:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-01 Made available in DSpace on 2013-09-30T17:56:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:16:07Z No. of bitstreams: 0 Made available in DSpace on 2014-05-20T13:16:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-01 The objective of this work was to evaluate the skin, liver and kidney histology of young pacus supplemented in diet with trivalent chromium and to evaluate the residue of chromium in water effluent. Randomised delineation by using factorial scheme 4x2, with four levels of chromium (0, 6, 12, 18 mg/L), two stocking densities (4 and 20 kg/m(3)), and four repetitions were used. Pacus with 100 g were used, for 90 days. An increase of the number of mucus cells and club cells in the epidermis of the pacus supplemented with 18 chromium mg/kg was observed in any stocking density. The same effect was observed in the liver, and in the highest density (20 kg/m(3)) the alterations already occurred at the level of 6 mg/kg with the inclusion of chromium, initially with congestion of sinusoids and getting worse at the level of 18 mg/kg with necrosis. The kidney didn't present visible morphologic alterations when supplemented and submitted to the stocking densities. The concentration of chromium in the effluent of pacus was 3.27 mu g/L in the higher level of supplementation (18 mg/L). In conclusion the level of 18 supplement mg/kg was not shown beneficial to the growth of pacus and the stocking density, due to the possible stress, accelerated the alteration histology process of tissues. Univ Estadual Paulista, Ctr Aquicultura, São Paulo, SP, Brazil Univ Estadual Paulista, Dept Patol Vet, Fac Ciencias Agr & Vet, BR-14870000 São Paulo, Brazil Univ Estadual Paulista, Ctr Aquicultura, São Paulo, SP, Brazil Univ Estadual Paulista, Dept Patol Vet, Fac Ciencias Agr & Vet, BR-14870000 São Paulo, Brazil