Acute toxicity to herbicides to Oreochromis niloticus

Submitted by repositorio ufvjm (repositorio@ufvjm.edu.br) on 2017-01-06T14:37:50Z No. of bitstreams: 2 S0100-83582009000300024.pdf: 222091 bytes, checksum: 2797ea8c2cb6b664b5a9cbac82a502a2 (MD5) license.txt: 2109 bytes, checksum: aa477231e840f304454a16eb85a9235f (MD5)Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2017-03-06T17:53:19Z (GMT) No. of bitstreams: 2 license.txt: 2109 bytes, checksum: aa477231e840f304454a16eb85a9235f (MD5) S0100-83582009000300024.pdf: 222091 bytes, checksum: 2797ea8c2cb6b664b5a9cbac82a502a2 (MD5)Made available in DSpace on 2017-03-06T17:53:19Z (GMT). No. of bitstreams: 2 license.txt: 2109 bytes, checksum: aa477231e840f304454a16eb85a9235f (MD5) S0100-83582009000300024.pdf: 222091 bytes, checksum: 2797ea8c2cb6b664b5a9cbac82a502a2 (MD5) Previous issue date: 2009Funda??o de Amparo ? Pesquisa do Estado de Minas Gerais (FAPEMIG)Empresa de Pesquisa Agropecu?ria de Minas Gerais (EPAMIG)Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)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 concentra??es de atrazina (0; 2,5; 5; 10; e 20 mg L-1), visando a determina??o da concentra??o letal a 50% dos indiv?duos (CL50), e, no segundo, a sensibilidade ?s 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 ap?s exposi??o aos produtos. No primeiro ensaio foi observado elevado decl?nio na sobreviv?ncia dos alevinos a partir de 3 mg L-1 do herbicida atrazina, com CL50 estimada de 5,02 mg L-1. No segundo, a mistura alachlor + atrazina promoveu o maior efeito de mortalidade sobre os alevinos de til?pia. Com 72 horas de exposi??o, a escala de intoxica??o evidenciou redu??o nos n?meros de indiv?duos 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 CL50 obtida para o atrazina ? inferior ?quela mencionada como t?xica 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.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 CL50 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 CL50 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