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

The ability to regenerate can vary across an animal’s 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.