A Case for Debate in Planarian Regeneration,
an article summary by Christopher Paquette, BIOL 490 Fall 2014

For years researchers have debated the mechanism used by planarians to exhibit their impressive regeneration characteristics. Some have argued that planarian cells dedifferentiate in order to grow/repair areas of extensive damage, while others argued that planarians regenerate using stem cells called neoblasts. Baguna et al. (1989) used a cellular manipulation technique to analyze the planarian’s regeneration in hopes of testing the hypothesis that neoblasts are responsible for their regeneration and not dedifferentiation. Using Dugesia tigina and Dugesia mediterranea as their study subjects, researchers stimulated regenerative growth by lacerating them after they had been irradiated to neutralize normal cellular function. After irradiation, some planarians were injected with neoblast cell cultures, while others were injected with differentiated cell cultures. Their survival and regeneration times were recorded over a 60 day span. Neoblast-injected planarians were found to be the only experimental group to produce surviving individuals, as all non-irradiated controls showed a full recovery after the laceration. It was also discovered that the neoblasts from the sexual race of D. mediterranea can be injected into the asexual race to convert them into sexual ones. These discoveries suggest that neoblasts are true totipotent stem cells and serve as the basis for the regenerative growth of these planarian species. This sets planarians apart from many other organisms which use dedifferentiation as their mechanism for regeneration, and may shed light on the extent of regeneration being produced through these two very different methods.

Baguna J., Saló E., & Auladell C. 1989. Regeneration and pattern formation in planarians III evidence that neoblasts are totipotent stem cells and the cells. Development 107(1): 77-86.