Unexpected results and open questions from experiments on regeneration in lumbricid worms

Abstract

Lumbricid worms are commonly subjected to noxious stimuli leading to expulsion of celomic fluid or to loss of body segments; therefore regeneration of lost segments and restoration of the depleted cellular and soluble components of celomic fluid are of fundamental importance for these animals. Series of experiments was performed on regeneration abilities in well-defined epigeic species Eisenia andrei, E. fetida and Dendrobaena veneta, and endogeic Aporrectodea caliginosa. Efficient regeneration of the lost anterior or posterior segments was consistently observed in Eisenia sp. In a sharp contrast, D. veneta regenerated amputated anterior segments or extirpated suprapharyngeal ganglia (‘brains’) while regeneration of posterior segments was never recorded so far in this species. In A. caliginosa a loss of posterior segments was followed either by compensatory body growth or by formation of regeneration blastema. In all species regeneration was cold-inhibited while was resistant to cadmium soil pollution. The efficiency of regenerative processes in E. andrei and E. fetida might be connected with quality and quantity of some components of their celomic fluid; lysenin is unique for these species and riboflavin is much more abundant in Eisenia sp. than in other lumbricids investigated so far.