Olms and Mudpuppies: Proteidae

Physical characteristics: Olms are long and thin and have pale, pinkish white skin. The head is flat and narrow, and the eyes are tiny. Three pink gills stick out from each side of the head. The legs are small, and there are only three toes on the front feet and two toes on the rear feet. These features are thought to be adaptations to living in underground waterways. Some olms turn darker when exposed to light. These olms have larger eyes than do olms that never leave their caves. Olms have a squared-off snout and a short tail that is flat from side to side. They reach a length of about 12 inches (30 centimeters) from tip of snout to tip of tail.

Geographic range: Olms live in Europe from the Dinaric Alps of Slovenia and Italy in the north to Montenegro in the south.

Olms live in underground lakes and rivers in limestone caves. (Illustration by Joseph E. Trumpey. Reproduced by permission.)

Habitat: Olms live in underground lakes and rivers in limestone caves.

Diet: Olms feed at night, using chemical sensors to find small crustaceans and insects and other invertebrates.

Behavior and reproduction: Olms are friendly to one another except during the breeding season, when they defend their territory. Olms are secretive and rarely seen, except when they leave their caves either to feed or because of flooding. Breeding is not related to the seasons. Fertilization takes place inside the female's body after she picks up a sperm bag that has been released by a male. The fertilized (FUR-teh-lyzed) eggs are large and yellowish and are laid under rocks and other cover and guarded by the female. The eggs hatch in about six months. Larvae develop directly into adults without going through metamorphosis. Scientists believe some olms give birth to a pair of well-developed young rather than laying a batch of eggs.

Olms and people: Olms are a tourist attraction. They are popular in the pet trade and are used in scientific research.

Conservation status: The World Conservation Union (IUCN) lists olms as Vulnerable, or facing high risk of extinction in the wild. ∎