The Olm (Order: Caudata, Family: Proteidae)
The olm are cave dwelling, aquatic vertebrates that have descended from an ancient branch of salamanders: they have evolved independently for one-hundred-and-ninety million years (since the early Jurassic period, in the era of the dinosaurs), but they are now a threatened species due to pollution and loss of habitat.
The olm prefer underground water systems that are calm, well-oxygenated, and maintain a constant, year-round temperature of 6-12°C. The creatures have found a niche in the underground caves of the Dinaric Alps in north-eastern Italy and Boznia and Herzegovina. They are social animals, and populations have been discovered close to ground-level and as deep as three-hundred meters beneath the surface.
Olm do not metamorphose like most other salamanders; they maintain their larval characteristics throughout their aquatic existence: their eyelids never grow in, and they retain feathery gills and a tail fin. They are pale creatures with skin-covered eyes; they cannot see objects, but their eyes are light sensitive. They hunt in pitch-darkness, using enhanced senses of smell, taste, hearing, and an additional faculty of electrosensitivity (recently, it has been suggested that the olm may also use the Earth’s magnetic field for orientation).
Olm are capable of consuming excessive quantities of nutrients for storage as fats and sugars in their liver; and, when food is in short supply, they can reduce their metabolism. If sustenance is unavailable for a prolonged period, they are able to reabsorb their own tissues. They can live for ten years without food.