Toxicidade aguda de herbicidas a tilápia (Oreochromis niloticus)

Abstract

RESUMO -Esta pesquisa teve como objetivo avaliar a sensibilidade de alevinos de Oreochromis niloticus a diversos herbicidas. Para isso, foram realizados dois ensaios, sendo, no primeiro, avaliadas concentrações de atrazina (0; 2,5; 5; 10; e 20 mg L -1 ), visando a determinação da concentração letal a 50% dos indivíduos (CL 50 ), e, no segundo, a sensibilidade às mesclas dos herbicidas alachlor + atrazina (5,33 + 5,33 mg L -1 ), diuron + MSMA (5,33 + 2,13 mg L -1 ), paraquat (1,33 mg L -1 ) e 2,4-D + picloram (1,28 + 0,34 mg L -1 ), com contagem de mortes 96 horas após exposição aos produtos. No primeiro ensaio foi observado elevado declínio na sobrevivência dos alevinos a partir de 3 mg L -1 do herbicida atrazina, com CL 50 estimada de 5,02 mg L -1 . No segundo, a mistura alachlor + atrazina promoveu o maior efeito de mortalidade sobre os alevinos de tilápia. Com 72 horas de exposição, a escala de intoxicação evidenciou redução nos números de indivíduos de, aproximadamente, 17,4% para os produtos paraquat, 2,4-D + picloram e diuron + MSMA e de 100% para alachlor + atrazina. Os dados permitem concluir que a CL 50 obtida para o atrazina é inferior àquela mencionada como tóxica para truta e que a mistura alachlor + atrazina pode ser caracterizada como de risco para O. niloticus, mesmo quando aplicada em doses normais de uso.Palavras-chave: alachlor, atrazina, 2,4-D, diuron, paraquat, picloram.ABSTRACT -Two assays were carried out to evaluate Oreochromis niloticus sensitivity to different herbicides. In the first experiment, atrazin concentrations (0; 2.5; 5; 10 and 20 mg L -1 ) were evaluated aiming to determine lethal concentration (LC50) to O. niloticus. In the second assay, the effects of the herbicide mixtures alachlor + atrazin (5.33 + 5.33 mg L -1 ), diuron + MSMA (5.33 + 2.13 mg L -1 ), paraquat (1.33 mg L -1 ) and 2,4-D + picloran (1.28 + 0.34 mg L -1 ), were evaluated on O. niloticus survival after 96 h of exposure. In the first assay, a sharp decrease in fingerlings survival was observed from 3 mg L -1 of atrazin with CL 50 value of 5.02 mg L -1 and a high biomass decrease due to herbicide presence. In the second assay, a greater negative effect was observed on fingerlings by alachlor + atrazin. . After 72 h of incubation, intoxication rate showed a reduction in the number of individuals of 17.4% for paraquat, 2,4 D + picloram and diuron + MSMA, and of 100% for alachlor + atrazin. It was concluded that CL 50 obtained for atrazin is inferior to that listed as toxic to trouts and that the alachlor + atrazin mixture can be characterized as a risk to O. niloticus, even when applied at commercially recommended rates.

Pesticide Tank Mixes: An Environmental Point of View

“…Several parameters have been used to determine the xenobiotic effects in different organisms. Among these variables, the lethality [50][51], immobility [52], gill alterations [53][54][55][56], and reproduction [57][58][59] are pointed out.…”

Herbicides and the Aquatic Environment

“…For example, Botelho et al (2009) studied the toxicity of various herbicides for tilapia (Oreochromis niloticus) including atrazine, paraquat and some mixtures as alaclhor + atrazine, diuron + MSMA and 2,4D + picloram. The LC 50 (96 hours) was 5.02 mg.L -1 for atrazine.…”

Evaluation of lambda-cyhalothrin oxidative stress and gonad histoarchitecture toxicity potency in Clarias gariepinus

“…Researches have revealed that it is moderately toxic to mammals and highly toxic to fish and other aquatic invertebrates as well as bees (Anadon et al, 2006;Ratnasooriya et al, 2003). It has been reported that the aquatic organisms are highly vulnerable to pesticides contamination as run-offs from farms and industries end up in water bodies (Botelho, Santos, & Oliveira, 2009;Nnamonu et al, 2018). Some substantial hazard in the environment occurs due to pesticides uptake and accumulation in the food chain (Somdare, 2015).…”