Effect of Butachlor Herbicide on Earthworm Eisenia fetida—Its Histological Perspicuity

With the advent of the Green Revolution, there has been a quantum leap in the use of synthetic herbicides and pesticides throughout the world to sustain high yielding crop varieties. Continuous use of these synthetic chemicals leads to loss of soil fertility and soil organisms. To explore the effect of exposure to commercial herbicide (Butachlor) on the life history parameters (biomass, clitellum development, and cocoon production) and the histological changes in the earthworm Eisenia fetida over 60 days, the dried cow dung was contaminated with 0.2575？mg , 0.5150？mg , and 2.5750？mg of butachlor based on the value, and a control was maintained. The mean earthworm biomass was found to be decreased with increasing herbicide concentration. Similarly, cocoon production was also reduced by the increasing herbicide concentration. A possible explanation is an increased demand for energy, needed for the regulation and detoxification of herbicide. All earthworms in the exposed group were found to have glandular cell enlargement and to be vacuolated. 1. Introduction Earthworms are often used as test organisms because of their important function, for example, as decomposer [1] and their sensitive reactions towards environmental influences. Earthworms are ecologically very important because there may be a risk secondary poisoning through feeding on worms contaminated by toxic substances. This could occur whether or not the worms themselves suffer any adverse effects. However, for most chemicals doses, which are toxic to birds or mammals and toxic to worms too, in such poisoning incidents, dead worms are found with affected predators [2, 3]. For that reason, earthworms are regarded as a reference compartment to observe soil contaminant bioavailability [4]. They are used to evaluate the lethal and sublethal effects of chemical contaminants and pollutants. Therefore they are useful to assess the contaminant fractions which may act on all organisms getting in touch with soil. Earthworms have been shown to be affected by the fate of herbicides in soil. Earthworms directly influence the persistence of herbicides in soil by metabolizing a parent compound in their gut [5, 6], by transporting herbicides to depth and increasing the soil bound (non extractable herbicides) fraction in soil or by absorbing herbicide residues in their tissues. The OECD earthworm toxicity test number 207 is widely used for terrestrial ecotoxicological test which is applied both in prospective and increasingly in retrospective ecotoxicological research. The present work reveals clearly that