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.

Live foldscope imaging of two environmentally beneficial earthworm species and their early developmental stages

“…Certain earthworm species can regenerate very fast, especially; epigeic earthworm species tend to regenerate quickly. Epigeic earthworm species remain in an unpredictable environment tolerate to a wide range of temperature and humidity and exposed to predator, pressure, and agricultural practices hence it is easy to regenerate lost segments by altering the levels of neurohormones secreted by ventricular nerves and ganglia; in contrast, deep soil-dwelling earthworms, which are devoid of predator pressure and remain in a predictable environment, generally they do not have the power to regenerate, because their cerebral neurohormone inhibits regeneration (Banik & Chaudhuri, 2016;Bhattacharjee & Chaudhuri, 2020;Nanda & Chaudhuri, 1983;Okrzesik et al, 2013).…”

“…This vermicast is rich in humus, micronutrients, enzymes, vitamins, and plant growth hormones, which promote plant growth and inhibit pathogenic microbes (Aira et al., 2006). Vermicast protects crop plants from pests and diseases by improving water‐holding capacity, soil quality, pH, fertility, and productivity (Adhikary, 2012). Vermicompost is an excellent source of biofertilizer that improves the physicochemical and biological properties of agricultural soils.…”