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Ecología Aplicada

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IANNACONE, José  and  ALVARINO, Lorena. Ecotoxicological effect of methomyl on Corydoras Lacépède, 1803 (Siluriformes: callichthyidae) and its leukocyte characterization. Ecol. apl. [online]. 2008, vol.7, n.1-2, pp.55-61. ISSN 1726-2216.

Methomyl is a carbamate acetylcholinesterase inhibitor that acts by contact and systemically and is one of the agrochemicals of mayor use as insecticide-acaricide to control a broad spectrum of agricultural pests. Peru lacks information regarding hematological aspects of bony fishes which could be used as potential physiological biomarkers of sub lethal responses in ecotoxicological bioassays. Aims of the current research were: 1) evaluate acute toxicological effect of methomyl on an ornamental Amazonian fish Corydoras arcuatus Elwin, 1939 (Callichthyidae) at 2, 4, 6, 8, 24 and 48 h exposure, and 2) characterize leukocytes of C. arcuatus, Corydoras leucomelas Eigenmann & Allen, 1972 and Corydoras leopardus Myers, 1933, and determinate quantitative reference values. Bioassays with methomyl were performed on plastic pots of 1000 mL. Values of LC50 (mg AI L-1) were 10.84; 3.18; 0.28; 0.01; 0.002 and < 0.002 at 2, 4, 6, 8, 24 and 48 h, respectively. LT50 at the lower concentration of 3.2 mg L-1 was 4.83 h. Blood extraction, was done by the cardiac puncture method, and smears were stained with Giemsa and Wright. Differences on leukocytes counts were not observed in both staining procedures, but slight differences between sexes were found Non significant differences between species of Corydoras were observed. Quantitatively, the following sequence was found: lymphocytes (64.6%)> monocytes (18.4%)> neutrophiles (8.2%)> eosinophiles (5.2%)> basophiles (3.2%). Blood parameters obtained contribute to the knowledge of this genus and could be potentially employed as biomarkers of sublethal responses in ecotoxicological bioassays.

Keywords : Amazonía; Corydoras; lethal effect; methomyl; leukocytes; hematological parameters; environmental risk.

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