Olm, (Proteus anguinus), is a blind salamander belonging to the family Proteidae (order Caudata). It lives in the subterranean streams in karst areas of the Adriatic coast from northeastern Italy southward into Montenegro.
It can be found in the underwater caves of Italy, Slovenia, Croatia, and Bosnia and Herzegovina. Olm is a distant relative of the axolotl. It belongs to the group of ancient amphibians that developed 190 million years ago. Unfortunately, olm is classified as vulnerable due to increased pollution of the water in its natural habitat.
It has spent so long adapting to life in caves that it’s mostly blind, hunting instead with various supersenses including the ability to sense electricity. It never grows up, retaining the red, feathery gills of its larval form even when it becomes sexually mature at sweet sixteen.
It stays this way for the rest of its remarkably long life, and it can live past 100 years. You can make out an olm’s organs through its skin. The skin is translucent because the salamanders are adapted for living in underwater caves in pitch-black darkness, so they don’t need to produce any colored pigment.
Olms can go 10 years without eating using glycogen and lipids stored in the liver. They have no natural predators, few stressors, and — as cold-blooded amphibians — no need to maintain body heat. Simply put, they just don’t need a ton of energy to survive. Olms can reach 1 to 16 inches in length and 0.1 to 5.3 ounces in weight. Females are slightly larger than males.
Olm is also known as a “human fish” because of its human-like, pinkish skin. Olms have pear-shaped heads, rounded snouts, and mouths filled with small teeth. It has a snake-like, elongated body, short, thin limbs with three fingers on the front and two fingers on the hind legs, and a short, flat tail surrounded by a thin fin. Adult olm has fully-developed lungs, but they are not used for breathing because of the aquatic lifestyle of this animal. Olm breaths via three pairs of short, red-colored, frilly gills located behind the head. despite their inability to see, they hunt their prey – small crabs, snails, and insects – in the waters of caves using well-developed sensory organs.
Olm is a gregarious animal that is often found in groups. Sexually active males are solitary and territorial. They aggressively defend their territory and produce pheromones to attract females.
Olms can mate all year round. The female lays 5 to 70 eggs in between the rocks and guards them until they hatch. Tadpoles are 0.7 inches long after hatching. They grow and attain the morphology of adults at the age of 4 months. Scientists aren’t exactly sure how many eggs a single female olm lays throughout her lifetime, though they estimate that it could be hundreds. But only two of those embryos are likely to survive to adulthood.
- karst, terrain usually characterized by barren, rocky ground, caves, sinkholes, underground rivers, and the absence of surface streams and lakes. It results from the excavating effects of underground water on massive soluble limestone. The term originally applied to the Karst (or Kras) physiographic region, a limestone area northeast of the Gulf of Trieste in Slovenia, but has been extended to mean all areas with similar features. Karsts are found in widely scattered sections of the world, including the Causses of France; the Kwangsi area of China; the Yucatán Peninsula; and the Middle West, Kentucky, and Florida in the United States. [Back]
- The axolotl, Ambystoma mexicanum, is a paedomorphic salamander closely related to the tiger salamander. Axolotls are unusual among amphibians in that they reach adulthood without undergoing metamorphosis. Instead of taking to the land, adults remain aquatic and gilled. The species was originally found in several lakes underlying what is now Mexico City, such as Lake Xochimilco and Lake Chalco. These lakes were drained by Spanish settlers after the conquest of the Aztec Empire, leading to the destruction of much of the axolotl’s natural habitat. Axolotls should not be confused with the larval stage of the closely related tiger salamander, which is widespread in much of North America and occasionally become paedomorphic. Neither should they be confused with mudpuppies, fully aquatic salamanders from a different family that are not closely related to the axolotl but bear a superficial resemblance. [Back]
Mary Bates Ph.D. Science Writer
The New Yorker