Salamander limb regeneration mystery solved.

I've always wondered about this. Now if only this were in English... From Technology Review:

Salamanders have an enviable ability to regrow appendages that are amputated or injured; they re-create all the bones, muscle, skin, blood vessels, and nerves of the new body part so adeptly that it's hard to tell that it was ever missing. Because of this ability, salamanders have been popular subjects for scientists studying regeneration--and trying to learn how human cells might be coaxed to perform the same feat.

In salamanders, new tissues come from a tumorlike mass of cells that forms at the site of the injury, called the blastema. Until now, most scientists thought that the blastema contained a population of stem cells that had become pluripotent--capable of giving rise to all the needed tissues. But a new paper in the journal Nature provides evidence that this is not the case. Instead, stem cells involved in regeneration only create cells of the tissue that they came from. The finding suggests that regeneration does not require cells to reprogram themselves as dramatically as scientists had assumed.