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Proteus anguinus (aka blind cave salamander)
The olm has an eel-like body with a laterally flattened tail and a broad head with blunt snout. It is about a foot long. The legs are very short, with 3 toes on the front legs and 2 on the hindlegs, and directly behind the head on each side are three large, feathery, bright pink gills. Olms begin life with well developed eyes, but by the time they reach adulthood those eyes have retreated beneath the skin and the animal is blind. Olms also begin life with black skin, but lose their color as they grow into adulthood, although dark pigmentation can be induced by exposure to light (prolonged exposure to light is lethal to olms). On the ventral side of the body the skin is translucent and reveals the contours of internal organs. This species exhibits little sexual dimorphism in appearance, but females are larger than males.
Distribution and Habitat
Olms live in the underground rivers and pools of limestone caves from Slovenia southward through Croatia and Bosnia and Herzegovina, possibly into Montenegro and Serbia. They have also been introduced in the French Pyrenees Mountains and northeastern Italy. They usually reside deep within the cave system (as far as 985 feet below the surface), but may be found in open streams near the surface during times of high rainfall and flooding.
Olms will eat most anything they can capture and fit into their mouths, but have a preference for insects and insect larvae, small crustaceans, and small fish.
During times of breeding, males become territorial and physically defend their territories. Once a mating territory is established by the male, he waits for females. Eventually a female will approach a male within his territory and courtship begins. The male fans his tail towards the female's head and then touches her cloaca with his snout. When she reciprocates, he walks in front of her and deposits a spermatophore, which she immediately picks up with her cloaca and stores in a special structure called a spermathecae. Once the exchange is completed the male and female part company.
The female begins laying her fertilized eggs 2 to 3 days after courtship, and may continue to lay eggs for up to 25 days. Before laying her eggs, the female establishes an egg-laying territory away from the male's territory. Clutch size averages 35 eggs, but there can be as many as 70. Eggs incubate for two to six months, during which time the female "stands guard." The inch-long larvae lack limbs and gills, have well-developed eyes, and are almost black. It takes 86-182 days for them to develop into the adult form (development time increases in colder water). The female does not provide food or protection once the eggs are hatched.
Captive olms do not become sexually mature until about 10 years old, and have been known to live more than 50 years. Age of maturity and average lifespan in the wild are unknown. Captive olms only breed about every 12 years.
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Amphibians >> Order Caudata
This page was last updated on June 16, 2017.