Boyd, A. A. | Search bioRxiv

bioRxiv2025

Regrowing the growth zone: metamorphosis kickstarts regeneration in the annelid, Capitella teleta

The ability to regenerate can vary across an animals life history. We previously showed that Capitella teleta, an annelid worm, gains regenerative ability with age. Although larvae do not replace lost structures, juveniles and adults regenerate posteriorly following metamorphosis. To determine whether metamorphosis enables juveniles to regrow structures lost as larvae, we amputated C. teleta larvae, removing posterior segments, the hindgut, posterior growth zone, anus, and pygidium. Metamorphosis was then induced in these amputated larvae and reared as juveniles for 3-, 7-, or 14-days. New growth in juveniles was assessed by confocal microscopy, EdU staining, immunohistochemistry, and nuclear staining. A pgz and new segments were observed by 7 days post metamorphosis. Morphallaxis of the digestive system in preexisting tissue was also observed. In addition, re-amputation of juveniles resulted in regeneration of the pgz, segments, and hindgut. Our results demonstrate that amputated C. teleta larvae can metamorphose into functional juveniles capable of growing new segments, suggesting that metamorphosis acts as a switch to enable regeneration of structures essential for growth. This study highlights the impact of metamorphosis on changes in developmental plasticity. Summary statementThe annelid Capitella teleta can regain structures lost as a larva only after metamorphosis into a juvenile, indicating that metamorphosis may function as a switch in regeneration potential.

developmental biology↗

bioRxiv2023

Investigating the developmental onset of regenerative potential in the annelid Capitella teleta

An animals ability to regrow lost tissues or structures can vary greatly during its life cycle. The annelid Capitella teleta exhibits posterior, but not anterior, regeneration as juveniles and adults. In contrast, embryos display only limited replacement of specific tissues. To investigate when during development C. teleta becomes capable of regeneration, we assessed the extent to which larvae can regenerate. We hypothesized that larvae exhibit intermediate regeneration potential and demonstrate some features of juvenile regeneration, but do not successfully replace all lost structures. Both anterior and posterior regeneration potential of larvae were evaluated following amputation. Wound sites were analyzed for re-epithelialization, cell proliferation by EdU incorporation, stem cell and differentiation marker expression by in situ hybridization, presence of neurites and muscle fibers by immunohistochemistry and phalloidin staining respectively, and regrowth of structures. Wound healing occurred within 6 hours of amputation for both anterior and posterior amputations. Cell proliferation at both wound sites was observed for up to 7 days following amputation. In addition, the stem cell marker vasa was expressed at anterior and posterior wound sites. However, growth of new tissue was observed only in posterior amputations. Neurites from the ventral nerve cord were also observed at posterior wound sites. De novo ash expression in the ectoderm of anterior wound sites indicated neuronal cell specification, although the absence of elav expression indicated an inability to progress to neuronal differentiation. In rare instances, cilia and eyes reformed. Both amputations induced expanded expression of the myogenesis gene MyoD in pre-existing tissues. Our results indicate that amputated larvae complete early, but not late, stages of regeneration, indicating a gradual acquisition of regenerative ability in C. teleta. Furthermore, amputated larvae can metamorphose into burrowing juveniles, including those missing brain and anterior sensory structures. To our knowledge, this is the first study to assess regenerative potential of annelid larvae.

developmental biology↗