Restorative Regeneration of Digital Tips in the African Clawed Frog (Xenopus laevis Daudin)

Localized, specialized structures are carried on the tips of digits of many amniote and certain non‐amniote tetrapods. The pes of some members of Pipidae represents a rare example among tetrapods of differential expression of digital tip form (clawed vs. non‐clawed digits). As a step towards understanding how such localized forms are generated and maintained, we conducted a series of amputation experiments and observed, through the process of regeneration, the potential for reconstitution, at the tissue and organ level, of the different digit tip morphologies. Results of this study reveal that immediately following metamorphosis specialized digit tip structures are regenerated with a high degree of structural and spatial accuracy by a process that essentially replicates normal development in recently metamorphosed Xenopus laevis froglets. Furthermore, this regenerative capacity is maintained in juveniles 4 months beyond metamorphosis, and also in adults of 1 year or more in age, indicating that metamorphosis‐specific conditions do not exclusively facilitate regeneration of digit tips. In addition, regenerative capacity is maintained through repeated bouts of amputation and regeneration, indicating deep‐seated digit identity and retention of the distinct digit tip developmental programs within the digits. Together, these data suggest that the developmental programing responsible for the formation of the discrete digital tip morphologies is located regionally within each digit, and that it is retained through time. Our results suggest that Xenopus can serve as a model organism for exploring the molecular underpinnings of digit tip formation because regeneration leads to morphologically identical structures to those of the original digit tips. Anat Rec, 2011. © 2010 Wiley‐Liss, Inc.