Neuroendocrine control of posterior regeneration in tropical earthworm, Eudrilus eugeniae (Kinberg)

Abstract

Eudrilus eugeniae (Kinberg), well known vermicomposting earthworms, are often subjected to predator attacks leading to loss of body parts due to their surface living habit. Thus nature has gifted them the power of regeneration of lost body parts. As neurosecretion is the sole source of hormone in oligochaetes, we hypothesize that neurohormone secreted from the neurosecretory cells of the central nervous system (CNS) will control the phenomenon of regeneration in earthworms. In Eudrilus eugeniae, appearance of regeneration blastema was noticed within 72 h of posterior amputation. In fact, posterior amputation brought about multiple cytoplasmic alteration in the neurosecretory cells (NSCs) viz. deep stained A cells and moderately stained B cells in cerebral ganglia, deep stained 'U' cells and moderately stained B cells in the sub-esophageal and ventral nerve cord ganglia. Massive depletion followed by marginal accumulation of NSM in the NSCs following 24 h and 48 h of amputation were recorded. Thereafter (72 h and 96 h of amputation) moderate to massive engorgement of NSM in the B cells, coupled with spectacular increase in number of A cells were noticed. Sequential changes involved in the secretory dynamics of NSCs, as well as, NSM accumulation both within and periphery of the ganglia (perineurium) provides evidence for the utilization of materials through repaired vascular systems during posterior regeneration in E. eugeniae.