Variation in whole-body regeneration between Botrylloides morphs and species

ABSTRACT Regeneration is a characteristic of the animal kingdom, and regenerative capacity is limited to higher taxonomical levels. In contrast, some basal animals like urochordates maintain a unique regeneration capacity, such as undergoing whole-body regeneration (WBR), an ability not observed in other chordates. Botryllids are colonial urochordates that can recreate new bodies through WBR from solely vascular tissue within ~ 2 weeks. To date, some species from the botryllid family were reported to orchestrate WBR, including B. diegensis . This study provided two novel records of WBR of B. jacksonianum and B. aff. anceps along with the two distinct morphs of B. diegensis . Interestingly, B. aff. anceps executed twin-body regeneration while this was limited to one-body for B. jacksonianum and B. diegensis . Histological sections validate the formation of multiple niches during WBR. Furthermore, the process of regeneration is phenotypically more similar between B. aff. anceps and B. diegensis . In contrast, the type of WBR in B. jacksonianum is similar to vascular budding as the niches were built from the vascular epithelium without undergoing significant tissue remodelling.