Olm
Tagged: animal, animals, cat, invertebrateProteus anguinus
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A bizarre, permanently aquatic salamander that lives almost entirely underground, the olm is vulnerable to a variety of factors that threaten its restricted and specialized habitat. The olm is a strange and obscure amphibian. It is highly adapted to a habitat of underground streams, pools, and lakes, and shows a classic example of pedomorphism. This is an evolutionary change that results in the retention of juvenile characteristics in the adult form. The species does not exist as a terrestrial, lung-breathing salamander. During the course of its normal pattern of development the olm has become “frozen” in the larval stage, retaining the large, feathery external gills and laterally compressed tail, which it beats to propel itself through the water.
Adapted for Life in the Dark
The olm’s underground streams and pools occur in the “karst” landscape that is associated with limestone. Living in permanent darkness, it has only tiny rudimentary eyes that are covered by skin. Its larvae, on the other hand, have quite well-developed eyes, but they degenerate during life. The adults lack dark pigment in their skin, but vary in color, being white, pink, gray, or yellowy; younger individuals often have darker blotches on the skin. Unable to see, the olm must rely on other senses to find its food and for social communication. It has an excellent sense of smell, and its skin contains large numbers of tiny lateral line organs that are sensitive to water-borne vibrations. It uses its sense of smell and sensitivity to vibrations to detect the moving invertebrates on which it feeds. These senses are also important during aggressive interactions between males and during courtship and mating. As recently as 1994 a distinct form of the olm has been discovered. Given the status of a subspecies, Proteus anguinus parkelj is black, has well-developed eyes, and is found only in the Bela Krajuna region of southeastern Slovenia. Individuals have been observed emerging from caves at night and swimming around in open pools and streams.
Statistics:
- Olm (blind cave salamander) Proteus anguinus
- Family: Proteidae
- World population: Unknown
- Distribution: Southeastern Europe: the Adriatic coast from northern Italy to Montenegro (former Yugoslavia)
- Habitat: Caves and underground lakes and streams in limestone mountains
- Diet: Small aquatic invertebrates, mainly crustaceans
- Size: Length: 8-11 in (20-28 cm)
- Form: Large, flat head with rounded snout; white, pale-gray, pink, or creamy-yellow elongated body; darker blotches in younger animals; large pink, feathery external gills. Small rudimentary limbs
- Breeding: Any time of year. Eggs fertilized internally. Twelve to 70 eggs laid under a stone and guarded by female until hatched; alternatively, just 1-2 eggs develop inside body of female, who gives birth to well-developed larvae. Young mature at 7 years. Life span up to 58 years
- Related endangered species: None
Breeding
Living underground, the olm is not exposed to the seasonal variations in temperature and rainfall that are experienced by amphibians living on the surface. Water temperature in its cave habitat is more or less constant all year round. As a result, the olm has no obvious breeding season but may breed at any time of year. When breeding, the slightly smaller males become aggressive toward one another, defending their territory. If a female enters a male’s territory, he performs a tail-fanning display-similar to that of European newts-in which he beats the tip of his tail rapidly against his flank. This creates a water current that he directs toward the female, who receives both vibratory stimuli and odor cues. If she is sexually responsive, she will approach the male. He then turns away, stopping to deposit a packet of sperm (called a spermatophore) on the ground. The female follows him and passes over the spermatophore. As she does so, her cloaca (cavity in the pelvic region into which the genital ducts open) passes over the spermatophore, and the sperm is drawn up into her body. The female then creates a simple nest in the debris on the cave floor and lays a clutch of eggs. She guards them against predators until they hatch. Alternatively, between one and two eggs develop inside the body of the female, who gives birth to well-developed larvae.
Habitat at Risk
The olm’s specialized habitat requirements-places where there are underground caves containing water-mean that even under ideal conditions it will always be a rare species. Although it is reasonably safe from many of the changes that have adversely affected surface-living amphibians, such as habitat destruction, it is not wholly unaffected by events on the surface. Much of the water that fills the underground caves flows in from the surface, where it can become contaminated by a range of pollutants, such as agricultural runoff or industrial waste. It is believed that pollution is a major factor in the reduction of the olm population. The olm is a fascinating animal, both to scientists and to amateur enthusiasts. In the past olms were collected as pig food. Today it is collection by enthusiasts that is having a more serious effect on natural populations.
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