Olm
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2008-07-16T17:07:53Z
Bibliomaniac15
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/* Ecology and life history */ adverb
{{otheruses}}
{{This|'''Proteus''' the amphibian|Proteus (disambiguation)}}
{{featured article}}
{{Taxobox
| name = Olm
| status = VU
| status_system = iucn3.1
| trend = down
| status_ref =<ref name="iucn">{{IUCN2006|assessors=Arntzen ''et al''|year=2004|id=18377|title=Proteus anguinus|downloaded=11 May 2006}} Database entry includes a range map and justification for why this species is vulnerable</ref>
| image = Proteus_humanfish.jpg
| image_width = 250px
| image_caption = Olms in [[Postojna Cave]], [[Slovenia]]
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Amphibian|Amphibia]]
| subclassis = [[Lissamphibia]]
| ordo = [[Salamander|Caudata]]
| familia = [[Proteidae]]
| genus = '''''Proteus'''''
| species = '''''P. anguinus'''''
| binomial = ''Proteus anguinus''
| binomial_authority = [[Josephus Nicolaus Laurenti|Laurenti]], 1768
| subdivision_ranks = [[Subspecies]]
| subdivision =
<center>
* ''Proteus anguinus anguinus''
<small>[[Joseph Nicolai Laurenti|Laurenti]], 1768</small>
* ''Proteus anguinus parkelj''
<small>[[Boris Sket|Sket]] & Arntzen, 1994</small>
''(See text)''</center>
}}
[[Image:P anguinus2.jpg|thumb|200px|right|The olm]]
The '''olm''', or '''Proteus''' ('''''Proteus anguinus'''''), is a blind [[amphibian]] [[Endemism|endemic]] to the subterranean waters of caves of the [[Dinaric Alps|Dinaric]] [[Karst topography|karst]] of southern Europe. It lives in the waters that flow underground through this extensive limestone region including waters of the [[Soča]] river basin near [[Trieste]] in [[Italy]], through to southern [[Slovenia]], southwestern [[Croatia]], and [[Herzegovina]]. The olm is the only [[species]] in its [[genus]] ''Proteus'', the only [[Europe]]an species of the [[family (biology)|family]] [[Proteidae]], and the only European exclusively [[Troglobite|cave-dwelling]] [[chordate]]. It is also occasionally called the "human fish" by locals because of its human-like skin (translated literally from {{lang-sl|človeška ribica}} and {{lang-hr|čovječja ribica}}), as well as cave [[salamander]], or white salamander.<ref name="istria">[http://www.istrianet.org/istria/fauna/amphibians/proteus-anguinus1.htm Istria on the Internet – Proteus anguinus (Olm)]. Retrieved on 7 June 2007.</ref>
This animal is most notable for its adaptations to a life of complete darkness in its underground habitat. The olm's [[eye]]s are [[Vestigiality|undeveloped]], leaving it blind, while its other [[sense]]s, particularly those of [[olfaction|smell]] and [[hearing (sense)|hearing]], are acutely developed. It also lacks any [[biological pigment|pigmentation]] in its [[skin]]. In contrast to most amphibians, the olm is entirely [[aquatic animal|aquatic]], and it eats, sleeps, and breeds underwater. It also exhibits [[neoteny]], retaining [[larva]]l characteristics like external [[gill]]s into adulthood. <ref name="animal">{{cite book |author=Burnie D. & Wilson D.E. (eds.) |title=Animal |publisher=DK |location=London |year=2001 |pages=61, 435 |isbn=0-7894-7764-5 |oclc= |doi=}}</ref>
==Anatomy==
===External appearance===
The olm's body is [[snake]]like, 20–30 centimetres (8–12 in) long, with some specimens reaching up to {{convert|40|cm|in|0}}.<ref name="WEB01">Weber A. (2000). ''Fish and amphibia''. In: Culver D.C. ''et al.'' (ed.): ''Ecosystems of the world: Subterranean Ecosystems'', pp. 109–132. Amsterdam: [[Elsevier]]</ref> The trunk is cylindrical, uniformly thick, and segmented with regularly spaced furrows at the [[myomere]] borders. The [[tail]] is relatively short, laterally flattened, and surrounded by a thin fin. The limbs are small and thin, with a reduced number of digits compared to other amphibians: the front legs have three digits instead of the normal four, and the rear have two digits instead of five. Its body is covered by a thin layer of skin, which contains very little of the [[biological pigment|pigment]] [[riboflavin]],<ref>Istenic L. in Ziegler I. (1974). ''Riboflavin as "pigment" in the skin of'' ''Proteus anguinus'' L. Naturwissenschaften '''12''': 686–687.</ref> making it yellowish-white or pink in color.<ref name="animal"/> The internal organs can be seen shining through on the abdominal part of the body. The resemblance in color to human skin is the reason why the ''Proteus'' is called ''human fish'' in some languages. However, the olm's skin retains the ability to produce [[melanin]]. When exposed to light, it will gradually turn dark, and in some cases the [[larvae]] are also colored. Its pear-shaped head ends with a short, dorsoventrally flattened snout. The mouth opening is small, with tiny [[tooth|teeth]] forming a [[sieve]] to keep larger particles inside the mouth. The nostrils are so small as to be imperceptible, but are placed somewhat [[Anatomical terms of location#Left and right .28lateral.29.2C and medial|laterally]] near the end of the snout. The regressed [[eye]]s are covered by a layer of skin. The olm breathes with external [[gill]]s that form two branched tufts at the back of the head.<ref name="animal"/> They are red in color because the oxygen-rich [[blood]] shows through the non-pigmented skin. The olm also has rudimentary [[lung]]s, but their role in respiration is only accessory. The sexes are very similar in appearance, with males having a somewhat thicker [[cloaca]] than females.
===Sensory organs===
Cave-dwelling animals have been prompted, among other adaptations, to develop and improve non-visual sensory systems in order to orient in and adapt to permanently dark habitats.<ref>Schlegel P.A., Briegleb W., Bulog B., Steinfartz S. (2006). {{lang|fr|''Revue et nouvelles données sur la sensitivité a la lumiere et orientation non-visuelle chez Proteus anguinus, Calotriton asper et Desmognathus ochrophaeus (Amphibiens urodeles hypogés)''}}. Bulletin de la {{lang|fr|Société herpétologique de France}}, '''118''', pp. 1–31. {{fr icon}}</ref> The olm's sensory system is also adapted to life in the subterranean aquatic environment. Unable to use vision for orientation, the olm compensates with other senses, which are better developed than in amphibians living on the surface. It retains larval proportions, like a long, slender body and a large, flattened head, and is thus able to carry a larger number of [[sensory receptor]]s.
====Photoreceptors====
The eyes are regressed, but retain sensitivity to [[light]]. They lie deep below the [[Skin#dermis|dermis of the skin]] and are rarely visible except in some younger adults. Larvae have normal eyes, but development soon stops and they start regressing, finally atrophying after four months of development.<ref name="DUR01">Durand J.P. (1973). {{lang|fr|''Développement et involution oculaire de Proteus anguinus Laurenti, Urodele cavernicole''}}. Ann. Spéléol. '''28''', 193–208 {{fr icon}}</ref> The [[pineal body]] also has photoreceptive cells which, though regressed, retain visual pigment like the photoreceptive cells of the regressed eye. The pineal gland in ''Proteus'' probably possesses some control over the physiological processes.<ref name="LANG01">Langecker T.G. (2000). ''The effects of continuous darkness on cave ecology and caverniculous evolution''. In: Culver D.C. ''et al.'' (eds.): ''Ecosystems of the world: Subterranean Ecosystems'', pp. 135–157. Amsterdam: Elsevier</ref> [[Ethology|Behavioral]] experiments revealed that the skin itself is also sensitive to light.<ref name="HAW01">Hawes R.S. (1945). ''On the eyes and reactions to light of Proteus anguinus.'' Quart. Journ. Micr. Sc. N.S. '''86''':1–53</ref> Photosensitivity of the integument is due to the pigment [[melanopsin]] inside specialized cells called [[melanophore]]s. Preliminary immunocytochemical analysis support the existence of photosensitive pigment also in the animal's integument<ref name="KOS01">Kos M. (2000). {{lang|sl|''Imunocitokemijska analiza vidnih pigmentov v čutilnih celicah očesa in pinealnega organa močerila (Proteus anguinus, Amphibia, Urodela)''}} (''Immunocitochemical analysis of the visual pigments in the sensory cells of the eye and the pineal organ of the olm (Proteus anguinus, Amphibia, Urodela).'') PhD thesis. Ljubljana: [[University of Ljubljana]]. {{sl icon}}</ref><ref>Kos, M., Bulog, B. ''et al.'' (2001) ''Immunocytochemical demonstration of visual pigments in the degenerate retinal and pineal photoreceptors of the blind cave salamander'' (''Proteus anguinus''). Cell Tissue Res, '''303''', pp. 15–25.</ref>
==== Chemoreceptors ====
[[Image:P anguinus-head1.jpg|thumb|200px|right|The front part of the olm's head carries sensitive chemo-, mechano-, and electroreceptors.]]
The olm is capable of sensing very low concentrations of organic compounds in the water. They are better at sensing both the quantity and quality of prey by smell than related amphibians.<ref name="HUP01">Hüpop K. (2000). ''How do cave animals cope with the food scarcity in caves?''. In: Culver D.C. ''et al.'' (ed.): ''Ecosystems of the world: Subterranean Ecosystems'', pp. 159–188. Amsterdam: Elsevier</ref> The nasal [[epithelium]], located on the inner surface of the nasal cavity and in the [[Jacobson's organ]], is thicker than in other amphibians.<ref name="DC01">Dumas P. in Chris B. (1998). ''The olfaction in Proteus anguinus''. Behavioural Processes '''43''': 107–113</ref> The [[taste buds]] are in the [[mucous]] epithelium of the mouth, most of them on the upper side of the [[tongue]] and on the entrance to the gill cavities. Those in the oral cavity are used for tasting food, where those near the gills probably sense the chemical composition of water.
==== Mechano- and electroreceptors ====
The sensory [[epithelia]] of the [[inner ear]] are very specifically differentiated, enabling the olm to receive [[sound]] waves in the water, as well as [[vibration]]s from the ground. The complex functional-morphological orientation of the sensory cells enables the animal to register the sound sources<ref>Bulog B. (1989). ''Differentiation of the inner ear sensory epithelia of Proteus anguinus (Urodela, Amphibia)''. Journal of Morphology, '''202''', pp. 325–338.</ref><ref name="BUL01">Bulog B. (1990). {{lang|sl|''Čutilni organi oktavolateralnega sistema pri proteju Proteus anguinus (Urodela, Amphibia). I. Otični labirint''}} (''Sense organs of the octavolateral system in proteus Proteus anguinus (Urodela, Amphibia). I. Otic labyrinth''). Biološki vestnik '''38''': 1–16 {{sl icon}}</ref>
Little is known about the hearing of ''Proteus'', but occasionally observed reactions to sounds indicate its possibility (Bulog, personal observ.). As this animal stays [[neotenic]] throughout its long life span, it is only occasionally exposed to normal adult hearing in air which is probably also possible for Proteus as in most salamanders. Hence, it would be of adaptive value in caves, with no vision available, to profit from underwater hearing by recognizing particular sounds and eventual localization of prey or other sound sources, i.e. acoustical orientation in general. The ethological experiments indicate that the best hearing sensitivity of ''Proteus'' is between 10 Hz and up to 15,000 Hz.<ref>Bulog B. & Schlegel P. (2000). ''Functional morphology of the inner ear and underwater audiograms of Proteus anguinus (Amphibia, Urodela)''. Pflügers Arch '''439'''(3), suppl., pp. R165–R167.</ref> The [[lateral line]] supplements inner ear sensitivity by registering low-frequency nearby water displacements.
A new type of sensory organ has been analyzed on the head of ''Proteus'', utilizing light and electron microscopy. These new organs have been described as [[ampullary organ]]s.<ref>Istenič L. & Bulog B. (1984). ''Some evidence for the ampullary organs in the European cave salamander Proteus anguinus'' (Urodela, Amphibia). Cell Tissue Res. '''235''', pp. 393–402.</ref>
Like some other lower [[vertebrate]]s, the olm has the ability to register weak [[electric field]]s.<ref name="SB01">Schegel P. & Bulog B. (1997). ''Population-specific behavioral electrosensitivity of the European blind cave salamander, Proteus anguinus''. Journal of Physiology (Paris) '''91''': 75–79</ref> Some behavioral experiments suggest that the olm may be able to use Earth's [[magnetic field]] to orient itself. Recently, ''Proteus'' ''anguinus'' has been found to align itself with natural and artificially modified magnetic fields.<ref>Bulog B., Schlegel P. ''et al.'' (2002). ''Non-visual orientation and light-sensitivity in the blind cave salamander, ''Proteus'' anguinus'' (Amphibia, Caudata). In: Latella L., Mezzanotte E., Tarocco M. (eds.). 16th international symposium of biospeleology; 2002 Sep 8–15; Verona: Societé Internationale de Biospéologie, pp. 31–32.</ref>
==Ecology and life history==
[[Image:P anguinus1.jpg|thumb|200px|right|The olm swims by serpentine bending of the body.]]
The olm's [[embryo]]nic development takes 140 days, after which it takes another 14 years to reach sexual maturity. The larvae gain adult appearance after nearly four months, with the duration of development strongly correlating with water temperature.<ref name="DUR02">Durand J.P. & Delay B. (1981). ''Influence of temperature on the development of ''Proteus anguinus'' (Caudata: Proteidae) and relation with its habitat in the subterranean world''. Journal of Thermal Biology '''6'''(1): 53–57</ref> Unconfirmed historical observations of [[vivipary]] exist, but it has been shown that the females possess a [[gland]] that produces the egg casing, similar to those of [[fish]] and egg-laying amphibians.<ref name="ALJ01">Aljančič M., Bulog B. et al. (1993). ''Proteus – mysterious ruler of Karst darkness''. Ljubljana: Vitrium d.o.o. {{sl icon}}</ref> It was long thought that female olm gave birth to live young at lower temperatures and laid eggs at higher, but rigorous observations have not confirmed that. The olm appears to be [[ovipary|oviparous]].
The female lays up to 70 eggs, each about {{convert|12|mm|in|1}} in diameter, and places them between rocks, where they remain under her protection. The tadpoles are {{convert|2|cm|in|1}} long when they hatch and live on [[yolk]] stored in the cells of the digestive tract for a month.<ref name="AA01">Aljančič G. and Aljančič M. (1998). {{lang|sl|''Žival meseca oktobra: Človeška ribica (Proteus anguinus)''}} (''The animal of the month of October: olm''). Proteus '''61'''(2): 83–87 {{sl icon}}</ref>
Development of the olm and other [[troglobite]] amphibians is characterized by [[heterochrony]] – the animal does not undergo [[metamorphosis]] and instead retains larval features. The form of heterochrony in the olm is [[neoteny]] – delayed [[somatic]] maturity with precocious reproductive maturity, i.e. reproductive maturity is reached while retaining the larval external [[morphology (biology)|morphology]]. In other amphibians, the metamorphosis is regulated by the [[hormone]] [[thyroxine]], excreted by the [[thyroid]] gland. The thyroid is normally developed and functioning in the olm, so the lack of metamorphosis is due to the unresponsiveness of key [[Tissue (biology)|tissue]]s to thyroxine.<ref name="LANG01">Langecker T.G. (2000). ''The effects of continuous darkness on cave ecology and caverniculous evolution''. In: Culver D.C. ''et al.'' (eds.): ''Ecosystems of the world: Subterranean Ecosystems'', pp. 135–157. Amsterdam: Elsevier</ref>
[[Image:P anguinus-head.jpg|thumb|200px|right|Disproportionately elongated head with gills.]]
The olm swims by eel-like twisting of its body, assisted only slightly by its poorly developed legs. It is a [[predator]]y animal, feeding on small [[crab]]s, [[snail]]s and occasionally [[insect]]s.<ref name="animal"/> It does not chew its food, instead swallowing it whole. The olm is resistant to long-term starvation, an adaptation to its underground habitat. It can consume large amounts of food at once, and store nutrients as large deposits of [[lipid]]s and [[glycogen]] in the [[liver]]. When food is scarce, it reduces its activity and [[metabolism|metabolic rate]], and can also reabsorb its own tissues in severe cases. Controlled experiments have shown that an olm can survive up to 10 years without food.<ref name="BUL02">Bulog B. (1994). {{lang|sl|''Dve desetletji funkcionalno-morfoloških raziskav pri močerilu (Proteus anguinus, Amphibia, Caudata)''}} (''Two decades of functional-morphological research on the olm (Proteus anguinus, Amphibia, Caudata''). Acta Carsologica XXIII/19. {{sl icon}}</ref>
Olms are [[Social animal|gregarious]], and usually aggregate either under stones or in fissures.<ref name="GUI01">Guillaume O. (2000). ''Role of chemical communication and behavioural interactions among conspecifics in the choice of shelters by the cave-dwelling salamander Proteus anguinus (Caudata, Proteidae)''. Can. J. Zool. '''78'''(2): 167–173</ref> Sexually active males are an exception, establishing and defending territories where they attract females. The scarcity of food makes fighting energetically costly, so encounters between males usually only involve [[Display (zoology)|display]]. This is a behavioral adaptation to life underground.<ref name="ALJ01">Aljančič M., Bulog B. et al. (1993). ''Proteus – mysterious ruler of Karst darkness''. Ljubljana: Vitrium d.o.o. {{sl icon}}</ref>
Reproduction has only been observed in captivity so far.<ref name="ALJ01">Aljančič M., Bulog B. et al. (1993). ''Proteus – mysterious ruler of Karst darkness''. Ljubljana: Vitrium d.o.o. {{sl icon}}</ref> Sexually mature males have swollen cloacas, brighter skin color, two lines at the side of the tail, and slightly curled fins. No such changes have been observed in the females. The male can start courtship even without the presence of a female. He chases other males away from the chosen area, and may then secrete a female-attracting [[pheromone]]. When the female approaches, he starts to circle around her and fan her with his tail. Then he starts to touch the female's body with his snout, and the female touches his cloaca with her snout. At that point, he starts to move forward with a twitching motion, and the female follows. He then deposits the [[spermatophore]], and the animals keep moving forward until the female hits it with her cloaca, after which she stops and stands still. The spermatophore sticks to her and the [[sperm]] cells swim inside her cloaca where they attempt to fertilize her eggs. The courtship ritual can be repeated several times over a couple of hours.<ref name="ALJ01">Aljančič M., Bulog B. et al. (1993). ''Proteus – mysterious ruler of Karst darkness''. Ljubljana: Vitrium d.o.o. {{sl icon}}</ref>
Longevity is estimated at up to 58 years. <ref>Noellert A., Noellert C. (1992). ''Die Aphibien Europas''. Franckh-Kosmos Verlags GmbH & co., Stuttgart.{{de icon}}</ref> Individual specimens have been kept under semi-natural conditions in concrete basins for up to 70 years <ref>Prof. B. Bulog, personal observation</ref>
== Taxonomic history==
Olms from different cave systems differ substantially in body measurements, color and some microscopic characters. Earlier researchers used these differences to support the division into five different species, while modern herpetologists understand that external morphology is not reliable for amphibian systematics and can be extremely variable, depending on nourishment, illness, and other factors even varying among individuals in a single [[population]]. ''Proteus anguinus'' is now considered a single species. The length of the head is the most obvious difference among various populations – individuals from Stična, Slovenia, have shorter heads on average than those from Tržič, Slovenia, and the [[Istria]]n peninsula, for example.
=== Black ''Proteus'' ===
[[Image:P anguinus parkelj-head.jpg|thumb|200px|right|The Black ''Proteus'', a subspecies, has a shorter head with more-developed eyes compared with the common type.]]
[[Image:Researchventhole.jpg|thumb|200px|right|The research vent-hole in Jelševnik near Črnomelj, where quality checks of water and sediments are performed regularly, and where activities of Black ''Proteus'' are registered with [[IR]] camera.]]
[[Image:PresentationroomBlackProteus.jpg|thumb|200px|right|The Presentation room with ten posters and TV film ''Black Proteus: mysterious dweller of the Karst in Bela krajina'', located in the Zupancic House near Črnomelj.]]
The '''Black ''Proteus''''' (''Proteus anguinus parkelj'' <small>Sket & Arntzen, 1994</small>) is the only recognized subspecies of the olm, [[endemism|endemic]] to the underground waters near [[Črnomelj]], Slovenia, an area smaller than {{convert|100|km2|sqmi|0}}. It was first found in 1986 by members of the [[Slovenian Karst Research Institute]] who were exploring the water from Dobličice karst spring in the [[White Carniola|Bela krajina]] region.<ref name="ZSLO01">Sket B. ''et al.'' (ed.) (2003). {{lang|sl|''Živalstvo Slovenije''}} (''The animals of Slovenia''). Ljubljana: [[Tehniška založba Slovenije]]. ISBN 86-365-0410-4 {{sl icon}}</ref>
It has several features separating it from the [[type species|type subspecies]]:<ref name="SA01">Sket B. & Arntzen J.W. (1994). ''A black, non-troglomorphic amphibian from the karst of Slovenia: Proteus anguinus parkelj n. ssp (Urodela: Proteidae)''. Bijdragen tot de Dierkunde '''64''':33–53.</ref>
{| class="wikitable"
!Feature!!''Proteus anguinus anguinus''!!''Proteus anguinus parkelj''!!Notes
|-
! align="left" valign="top"| Skin
| valign="top"| Not pigmented. || Normally pigmented, dark brown or black in color. || valign="top"| The most obvious difference.
|-
! align="left" valign="top"| Head shape
| valign="top"| Long, slender. || Shorter, equally thick. Stronger jaw muscles visible as two bulbs on the top of the head.
|-
! align="left" valign="top"| Body length
| valign="top"| Shorter, 29–32 [[vertebra]]e. || valign="top"| Longer, 34–35 vertebrae. || Amphibians do not have a fixed number of vertebrae.
|-
! align="left" valign="top"| Appendages
| valign="top"| Longer. || valign="top"| Shorter. ||
|-
! align="left" valign="top"| Tail
| valign="top"| Longer in proportion to the rest of the body. || valign="top"| Shorter in proportion.
|-
! align="left" valign="top"| Eyes
| valign="top"| Regressed. || valign="top" | Almost normally developed, although still small compared to other amphibians. Covered by a thin layer of transparent skin, no eyelids. || valign="top"| Regressed eye of White Proteus shows first of all immunolabelling for the red-sensitive cone opsin. The eye of Black ''Proteus'' has principal rods, red-sensitive cones and blue- or [[UV]]- sensitive cones.
|-
! align="left"| Other senses
| valign="top"| Specific and highly sensitive. || valign="top"| Some sensory organs, particularly electroreceptors, less sensitive.
|-
|}
These features suggest that the Black ''Proteus'' has probably colonized underground habitats more recently and still retains some nontroglomorphic characteristics.
== Research history ==
The olm is supposedly first pictured as two pairs of [[snake]]s with [[wing]]s, which could represent gills, in a [[relief]] on a [[Venetia]]n stone fountain, probably originating from Karst.
The first written mention of the olm is in [[Janez Vajkard Valvasor]]'s ''[[The Glory of the Duchy of Carniola]]'' (1689) as a baby [[dragon]]. This was a reference to a folk story he did not really believe in. The first researcher to retrieve a live olm was a [[physician]] and researcher from [[Idrija]], [[Giovanni Antonio Scopoli|G.A. Scopoli]]; he sent dead specimens and drawings to colleagues and collectors.
[[Joseph Nicolai Laurenti]], though, was the first to briefly describe the olm in 1768 and give it the scientific name ''Proteus anguinus''. It was not until the end of the century that [[Carl Franz Anton Ritter von Schreibers]] from the [[Naturhistorisches Museum]] of [[Vienna]] started to look into this animal's anatomy. The animals were sent to him by [[Žiga Zois]]. Schreibers presented his findings in 1801 to The [[Royal Society]] in [[London]], and later also in [[Paris]]. Soon the olm started to gain wide recognition and attract significant attention, resulting in thousands of animals being sent to researchers and collectors worldwide. The basis of functional morphological investigations in Slovenia was set up by Prof. dr. [[Lili Istenič]] in the 1980s. More than twenty years the Research Group for functional morphological Studies of the Vertebrates in the Department of Biology (Biotechnical Faculty, [[University of Ljubljana]]), is one of the leading groups studying the olm under the guidance of Prof.dr. [[Boris Bulog]].<ref>Bulog B. et al. (2003). ''Black Proteus: mysterious dweller of the Karst in Bela krajina ''. Ljubljana: TV Slovenia, Video tape.</ref> There are also several cave laboratories in Europe, where olms have been introduced and are being studied. These are [[Moulis]] ([[France]]), [[Kent's Cavern]] ([[England]]), [[Han-sur-Lesse]] ([[Belgium]]) and [[Aggtelek]] ([[Hungary]]). They were also [[Introduced species|introduced]] into the [[Hermannshöhle]] ([[Germany]]) and [[Grote Oliero]] ([[Italy]]) caves, where they still live today.
The olm was used by [[Charles Darwin]] in his famous ''[[The Origin of Species]]'' as an example for the reduction of structures through disuse:<ref name="DARWIN01">Darwin C. (1859). ''On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life''. London: John Murray.</ref>
{{cquote|Far from feeling surprise that some of the cave-animals should be very anomalous…as is the case with blind Proteus with reference to the reptiles of Europe, I am only surprised that more wrecks of ancient life have not been preserved, owing to the less severe competition to which the scanty inhabitants of these dark abodes will have been exposed.}}
== Conservation ==
[[Image:Proteus anguinus dis.png|thumb|right|Range map.]]
The olm is extremely vulnerable to changes in its environment due to its adaptation to the specific conditions in caves. Water resources in the karst are extremely sensitive to all kinds of pollution.<ref>Bulog B., Mihajl K. ''et al.'' (2002). ''Trace element concentrations in the tissues of Proteus anguinus (Amphibia, Caudata) and the surrounding environment''. Water air soil pollut., '''136'''(1–4), pp. 147–163</ref> The contamination of the karst underground waters is due to the large number of waste disposal sites leached by rainwater, as well as to the accidental overflow of various liquids. The reflection of such pollution in the karst underground waters depends on the type and quantity of pollutants, and on the rock structure through which the waters penetrate. Self-purification processes in the underground waters are not completely understood, but they are quite different from those in surface waters. Among the most serious chemical [[pollutants]] are chlorinated hydrocarbon [[pesticide]]s, [[fertilizer]]s, polychlorinated biphenyls ([[Polychlorinated biphenyls|PCB]]s), which are or were used in a variety of industrial processes and in the manufacture of many kinds of materials; and metals such as mercury, lead, cadmium, and arsenic. All of these substances persist in the environment, being slowly, if at all, degraded by natural processes. In addition, all are toxic to life if they accumulate in any appreciable quantity. Slovenian caves became famous for the animals they contained and which could not be found elsewhere. Due to its rarity the olm is also popular among collectors, which can threaten the species by taking too many animals out of the habitat.
The olm is included in Appendices II and IV of the [[EU Habitats Directive]] (92/43/EEC).<ref name="EEC01">''EU Habitats directive'' (1992). [http://ec.europa.eu/environment/nature/nature_conservation/eu_nature_legislation/habitats_directive/index_en.htm].</ref> Appendix II seeks to preserve favorable conservation status in animal and [[plant]] species along with their [[habitat]]s by protecting the species or defining special areas of conservation. These areas of conservation form the [[Natura 2000]] network. Appendix IV further defines "animal and plant species of community interest in need of strict protection." Hunting or keeping a limited number of olm is allowed only under strictly controlled circumstances, determined by local authorities.
The olm was first protected in Slovenia in 1922 along with all cave fauna, but the protection was not effective and a substantial black market came into existence. In 1982 it was placed on a list of rare and endangered species. This list also had the effect of prohibiting trade of the species. After joining the [[European Union]], Slovenia had to establish mechanisms for protection of the species included in the EU Habitats Directive. The olm is included in a Slovenian [[red list]] of endangered species.<ref name="UL01">''Slovenian official gazette'' (2002).
[http://www.uradni-list.si/1/ulonline.jsp?urlid=200282&dhid=44228 no. 82, tuesday 24 september 2002]. {{sl icon}}</ref> The [[Postojna]] cave and other caves inhabited by olm were also included in the Slovenian part of the Natura 2000 network.
In Croatia, the olm is protected by the legislation designed to protect amphibians<ref name="NN01">{{lang|hr|''Pravilnik o zaštiti vodozemaca (2002)'', [http://www.nn.hr/clanci/sluzbeno/1999/1435.htm Državna uprava za zaštitu prirode i okoliša]}}. {{hr icon}}</ref> – collecting is possible only for research purposes by permission of the National Administration for Nature and Environment Protection. Conservation status in [[Bosnia and Herzegovina]] and [[Montenegro]] has not yet been defined.
On the [[IUCN Red List]], the olm is listed as vulnerable because of its fragmented and limited distribution and ever-decreasing population.<ref name="iucn"/>
==Cultural significance==
[[Image:SVN001.JPG|200px|right|thumb|A coin depicting the olm, in the old Slovenian national currency [[Slovenian tolar|tolar]].]]
The olm is a symbol of Slovenian natural heritage. The enthusiasm of scientists and the broader public about this inhabitant of Slovenian caves is still strong 300 years after its discovery. The [[Postojna cave]] is one of the birthplaces of [[speleology#cave_biology|speleobiology]] due to the olm and other rare cave inhabitants. The image of the olm contributes significantly to the fame of the Postojna cave, which Slovenia successfully utilizes for the promotion of [[eco-tourism]] in [[Postojna]] and other parts of Slovenian karst. Tours of the Postojna cave also include a tour around the speleobiological station – the Proteus [[vivarium]], showing different aspects of the cave environment.<ref name="vivarium">[http://www.postojnska-jama.si/?cat=81&lang=en&PHPSESSID=b59779a3f5babf443ef966f0264dc436 Destinacija Postojna]. Retrieved 7 June 2007.</ref>
The olm was also depicted on one of the [[Slovenian tolar]] coins, and was the namesake of ''Proteus'', the oldest Slovenian popular science magazine, first published in 1933.
==References==
{{reflist|2}}
== External links ==
{{Commons|Proteus anguinus}}
{{Wikispecies|Proteus anguinus}}
* [http://amphibiaweb.org/cgi-bin/amphib_query?query_src=aw_search_index&where-genus=Proteus&where-species=anguinus&rel-genus=equals&rel-species=equals AmphibiaWeb page for the olm]
* [http://www.showcaves.com/english/explain/Biology/ProteusAnguinus.html Flora and Fauna of Caves: Proteus anguinus]
* {{sl icon}} [http://www.proteus.si/?q=node/1 Proteus magazine]
* [http://camp.rrc-kp.si/praksa/proteus/index_en.htm Slovenian practice example: Human Fish (''Proteus anguinus'')]
* [http://www.arkive.org/species/GES/amphibians/Proteus_anguinus/ The olm on ARKive] – pictures, films
* {{sl icon}} [http://www2.pms-lj.si/najpred/proteus.html The olm] on the pages of the Slovenian Natural history museum.
* [http://www.globalamphibians.org/servlet/GAA?searchName=Proteus+anguinus The Global Amphibian Assessment - Proteus anguinus]
* [http://www.istrianet.org/istria/fauna/amphibians/proteus/index.htm Istria on the Internet, Fauna - Proteus anguinus]
[[Category:Amphibians of Europe]]
[[Category:Cave salamanders]]
[[Category:Monotypic animal genera]]
[[Category:Fauna of Slovenia]]
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