First evidence of progenesis in Triturus (Amphibia)

Paedomorphosis is defined as the retention of subadult morphology in reproductive adults. Two main processes can produce this heterochronic pattern : neoteny and progenesis, but progenesis has not been yet demonstrated in newts. Distinction between them can be obtained from the determination of age at first reproduction using the squelettochronological method. In this study, we sampled more than 300 Triturus alpestris in two populations : one in a French Alpine lake and the other in an Italian pond. Results show that paedomorphs from the Italian pond are mature earlier and at a smaller size than metamorphs (Progenesis) whereas paedomorphic and metamorphic newts from the French population do not differ in size and age (Neoteny). Adaptative significance of Paedomorphosis is discussed in relation to the stability of the aquatic habitat