Slovenian Salamander

I loved the cave in Postojna. It was magnificent to be in. But I also saw one of the most unusual things I've ever seen--a salamander that retains it's gills into adulthood. Postojna has the most number of cave-dwelling species of any cave, logging in a 84 species, but most of them are of the insect variety. The salamander is odd man out. And not attractive. At all.
The Olm, or Proteus (Proteus anguinus), is a blind amphibian endemic to the subterranean waters of caves of the Dinaric karst of southern Europe. It lives in the waters that flow underground through this extensive limestone region including waters of the Soča river basin near Trieste in Italy, through to southern Slovenia, southwestern Croatia, and Herzegovina. The olm is the only species in its genus Proteus, the only European species of the family Proteidae, and the only European exclusively cave-dwelling chordate. In Slovenia it is also known by the name močeril, which translates as "the one that burrows into wetness."
What is most notable (aside from it's profound homliness) for its adaptations to a life of complete darkness in its underground habitat. Darwin used it as an example of a reduction in features through disuse in 'The Origin of the Species'. The olm's eyes are undeveloped, leaving it blind, while its other senses, particularly those of smell and hearing, are acutely developed. It also lacks any pigmentation in its skin. In contrast to most amphibians, the olm is entirely aquatic, and it eats, sleeps, and breeds underwater. It has 3 toes on its forelimbs, but 2 toes on its hind feet. It also exhibits neoteny, retaining larval characteristics like external gills into adulthood, like the American amphibians, the axolotl and the mud puppy--so it is an unusual feature, but it is not alone.