Studies on Cocoons of Three Epigeic Earthworm Species Perionyx excavatus (Perrier), Perionyx ceylanensis (Michaelsen) and Eudrilus eugeniae (Kinberg) with SEM Observations

Present study deals with cocoon biology of tropical epigeic earthworm Perionyx excavatus (Perrier), Perionyx ceylanensis (Michaelsen) and Eudrilus eugeniae (Kinberg). Ultra structure observed under Scanning Electron Microscope (SEM) revealed that wall of the cocoon is porous (which helps in aeration) and the terminal part of the cocoon is softer than that of middle part which facilitates the hatching process. The size of the cocoon varies among the species and is related to the diameter and length of the clitellum. All the epigeic species under study are continuous breeder with high fecundity. Among the studied species shortest incubation period, highest fecundity and highest hatching rate were observed in P. ceylanensis. Cocoon production in these three epigeic species increases in summer and monsoon season and decreases in the winter season. Temperature is the limiting factor for cocoon production as well as incubation period of cocoon. Cocoon production was affected by temperature and body weight of the earthworm. Thus it can be considered that cocoon production in epigeic earthworm species depends on biological factor (body mass), as well as, ecological factor (temperature). Continuous breeding strategy, high fecundity, high rate of cocoon production, as well as high hatching rate, indicates greater usefulness of P. ceylanensis followed by E. eugeniae than P. excavatus in the vermiculture based biotechnology in North-East India.