One theory is that the de-differentiated cells are related to tumor cells since chemicals which produce tumors in other animals will produce additional limbs in newts.
In America, the Red-spotted Newt (Diemictylus viridescens) is one of the most abundant species.
Research on newts is rare because they take two years to reach sexual maturity.
The history of the word newt is interesting. The oldest form of the name is eft, which is still used for some varieties, but according to the Oxford English Dictionary it changed for unknown reasons first to euft and then to ewt. For some time then it was an ewt, but then the N moved over and it became a newt. See A, an for other examples.\n