Abstract

RAFAEL, SERGIO EZEQUIEL et al. SUSCEPTIBILIDAD DE Octolasion cyaneum (ANNELIDA: OLIGOCHAETA, LUMBRICIDAE) EXPUESTA A CLORPIRIFOS EN CONDICIONES DE LABORATORIO. Cienc. suelo [online]. 2015, vol.33, n.2. ISSN 1850-2067.

Earthworms participate in soil ecosystem services and are considered potential indicators of soil health. The use of insecticides in agriculture may negatively affect the population of these earthworms. The aim of , this study was to evaluate: 1) the avoidance and / or attraction of Octolasion cyaneum (Oligochaeta, Lumbricidae) in the presence of Chlorpyrifos and 2) the lethal and sublethal effects of this insecticide on O. cyaneum. Avoidance, sublethal toxicity and reproduction bioassays were performed with 5 doses of Chlorpyrifos and a control with no chemical treatment. The proportion of individuals in the treated area, measured as the ratio of the weight of the treated area and the total weight of O. cyaneum did not differ among the different doses after 48 hours (p > 0.05). Therefore, there was no avoidance response of O. cyaneum to Chlorpyrifos. With different Chlorpyrifos doses, 238 individuals of O. cyaneum resulted alive and 2 dead, whereas 33% of the organisms presented morphological changes such as coiling and skin coloration. Twenty-eight days after application (DAA), damage percentage increased as the dose of Chlorpyrifos was higher (p = 0.051). Wet weight biomass (mg) of O. cyaneum did not differ between doses 7, 21 and 28 DAA, whereas it did vary 14 DAA (p = 0.004). Across all treatments including the controls, both O. cyaneum cocoons and juveniles numbers, were, on average, low. Therefore, Chlorpyrifos did not cause an avoidance behaviour response or a lethal effect on O. cyaneum. However, depending on the application rate, Chlorpyrifos produced morphological and biomass changes on these organisms.

Keywords : Bioassays; insecticide; earthworms.

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