Understanding the Role of the Clitellum in the Regeneration Events of the Earthworm <b><i>Eudrilus eugeniae</i></b>

Abstract

Regeneration is a complex mechanism to restore lost or damaged body parts. In earthworms, regeneration capability varies among different species, and it is important to explore the mechanism behind the regeneration process. Interestingly, regeneration in earthworms is either dependent or independent of clitellum segments. In the present study, juvenile earthworms (Eudrilus eugeniae) were amputated at 3 different sites, namely the head, clitellum, and tail segments (at segments 10, 15, and 30, respectively), and their regeneration ability was documented using a foldscope. The amputated segments having the intact clitellum were able to heal the wounds and form the regenerative blastema. The smaller portions of the amputated segments (segments 1-10 and 1-15) without intact clitellum were unable to heal the wound, and death occurs within 12-24 h. The larger portions of the amputated segments (segments 15 and 30 to anus) without intact clitellum were able to heal the wound but lacked the regeneration capability. In control worms, al-kaline phosphatase (ALP) signals were observed at the anterior tip, clitellum, and gut epithelium tissues, whereas, upon amputation, the enriched signals from the clitellum diminished, but profound signals were observed at the amputation site and regenerative blastema. Interestingly, on days 3 and 4, blastemal tips lacked ALP signals due to initiation of the differentiation process in the regeneration blastema. In summary, using a foldscope microscope, the role of the clitellum in the regeneration mechanism was indicated by ALP activity.

Expression of Alpha-Fetoprotein in the Earthworm Eudrilus Eugeniae

“…Finally, the posterior regions contain prostate glands, intestine and anus from the 19 th to remaining segments (Fig1.A). Previous studies revealed that clitellar segments acted a pivotal role in earthworm E. eugeniae[2,5,8]. The Fig.1B to D clearly explain the importance of clitellum in the regeneration.…”

“…The clitellum is important for the reproduction of the worm. The amazing regeneration ability and easy maintenance conditions make this an ideal animal model for studies on regeneration and stem cells [1][2][3][4][5][6]. The regeneration in E. eugeniae begins with a proliferating mass of undifferentiated progenitor cells and subsequently forms the regenerative blastema [6].…”

“…The knockdown of TPT1 gene expression resulted the failure of both the disappearance of clitellar segmental puffiness and differentiation of clitellar granular epithelial cells [2]. It has been reported that the clitellum is essential for the successful regeneration [5,8,9]. But a further detail of clitellar segmental role in the successful regeneration is still unknown.…”

Foldscope microscope, an inexpensive alternative tool to conventional microscopy—Applications in research and education: A review

“…Earthworms have recently been used as animal models for regeneration research. Using the foldscope, our team explored the importance of the clitellum in earthworm regeneration ( Eudrilus eugeniae ) (Christyraj et al, 2019). Foldscope gives novice researchers new hope, demonstrating that study can be carried out and advanced even with rudimentary equipment.…”

Isolation and Molecular Characterization of a Fluorescence-Emitting Bacterium from the Gut of Earthworm, Perionyx excavatus (Perrier, 1872), and Its Symbiotic Association in Earthworm Regeneration

“…Earthworm, P. excavatus, has prodigious regeneration capability (14) has been studied extensively. Intense fluorescence was observed beneath the epithelial layer in the tissue sections of regenerating worms (Figure 10A).…”