Comparative histological studies in the gut of earthworms exposed to chemical fertilizer and organic manure

C.Esaivani; K.Vasanthi; K.Chairman

Volume : VII, Issue : II, February - 2017

Comparative histological studies in the gut of earthworms exposed to chemical fertilizer and organic manure

C. Esaivani, K. Vasanthi, K. Chairman

Abstract :

The present study has a strong focus on the practical aspects of the effect of chemical fertilizers and organic manure on the earthworms. The advent of Green revolution has lead to the use of chemical fertilizers and pesticides throughout the world to sustain high yielding crop varieties. Continuous and indiscriminate use of these chemicals has lead to the loss of soil fertility and soil organisms. Histopathological studies may signal a damaging effect of organisms resulting from prior or ongoing exposure to toxic agents. Monocrotophos is the most popular and widely used organophosphorus pesticide in agriculture. A large number of studies have reported general histological changes in earthworms. A fewer studies have reported more specific types of histopathological studies in Eisenia foetida, Dendrodrilus rubidus, Lumicus terrestris, Lumicus rubellus and Octolasium traspandanum. However none of the study was undertaken on earthworm Lampito mauritti which constitutes the dominant earthworm in crop fields of India. The earthworm Eudrilus eugeniae were reared in two different types of leaf litters namely Ficus benghalensis and Ficus racemosa mixed with cow dung in three different proportions such as 25%, 50% and 75% respectively. All parts of these plants are medicinally important. Large number of medicinal plants are claimed to possess anthelmintic activity. It has been demonstrated that all anthelmintics are toxic to earthworms and a substance toxic to earthworms is worthy for investigation as an anthelmintic. The aim of the study is to evaluate the changes in tissues of the earthworms that worked under field condition and also to compare the structural changes in tissues between worms exposed to chemical fertilizer and those worked in transforming the leaf litters into vermicompost. The findings of the present study clearly indicates that the changes observed in earthworms intestinal tract may have been caused by the exposure to over usage of pesticides and its residual availability in the soil may also be the case for the major alteration and damages observed in the tissues of earthworms exposed to pesticide monocrotophos at recommended field dose. The histology of earthworm which is subjected to various proportions of ficus leaf wastes and cow dung shows that increase in the concentration of litters gradually increase the damages of the tissues but the changes in tissues during vermicomposting were only minor damages when compared to that of the chemical fertilizer. Risk assessment is normally aimed at the protection of human health and the ecosystem, and the interrelationship of these two areas of protection is easy to perceive. The use of earthworms in risk assessment is to obtain more information on environmental quality and ensure environmental safety. There is an urgent need to test the chemicals causing toxicity to earthworms, and finding an alternative for the replacement of these chemicals is the need of the day, because earthworms play a major role in soil fertility as well as acting as a transferring route from the soil to the terrestrial ecosystem.