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62-532: This cave salamander is most notable for its adaptations to a life of complete darkness in its underground habitat. The olm's eyes are undeveloped , leaving it blind, while its other senses , particularly those of smell and hearing , are acutely developed. Most populations also lack any pigmentation in their skin . The olm has three toes on its forelimbs, but only two toes on its hind feet. It exhibits neoteny , retaining larval characteristics like external gills into adulthood, like some American amphibians,

124-615: A cave animal was focused upon a cave salamander, Proteus anguinus . It was originally identified as a "dragon's larva" by Johann Weikhard von Valvasor in 1689. Later, the Austrian naturalist Joseph Nicolaus Lorenz described it scientifically in 1768. Another early scientific description of a cave salamander was undertaken by Constantine Samuel Rafinesque in 1822 while he was a professor of botany and natural history at Transylvania University in Lexington, Kentucky . The species he described

186-508: 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

248-663: A few hours a day, but could not cause them to change to a land-dwelling adult form, as she and others had done with axolotl . The basis of functional morphological investigations in Slovenia was set up by Lilijana Istenič  [ de ] in the 1980s. More than twenty years later, the Research Group for functional morphological Studies of the Vertebrates in the Department of Biology (Biotechnical Faculty, University of Ljubljana ),

310-953: A number of cave systems as opposed to being continuous, and what they consider a decline in extent and quality of its habitat, which they assume means that the population has been decreasing for the last 40 years. Zagreb Zoo in Croatia houses the olm. Historically, olms were kept in several zoos in Germany, as well as in Belgium, the Netherlands, Slovenia and the United Kingdom. At present they can only be experienced at Zagreb Zoo, Hermannshöhle in Germany and Vivarium Proteus (Proteus Vivarium) within Postojnska jama (Postojna Cave) in Slovenia. There are also captive breeding programs in places like France. The olm

372-413: A thicker and more complex epidermis, increased sensory abilities, and the absence of hair and sebaceous glands. The ridges increase friction for improved grasping. Dermal papillae also play a pivotal role in hair formation, growth and cycling. In mucous membranes , the equivalent structures to dermal papillae are generally termed "connective tissue papillae", which interdigitate with the rete pegs of

434-469: A typical, very stable temperature of 8–11 °C (46–52 °F), infrequently as warm as 14 °C (57 °F). There have also been observations in northeastern Italy where they swim to the surface in springs outside the caves, even in daylight, where they occasionally feed on earthworms. The black olm may occur in surface waters that are somewhat warmer. The olm swims by eel-like twisting of its body, assisted only slightly by its poorly developed legs. It

496-477: 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. The olm is nevertheless noted for its capability of surviving higher concentrations of accumulated PCBs than related aquatic organisms. The olm

558-409: A worm and vermin of which there are many hereabouts". The first researcher to retrieve a live olm was a physician and researcher from Idrija , Giovanni Antonio Scopoli , who sent dead specimens and drawings to colleagues and collectors. Josephus Nicolaus 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

620-402: Is a predatory animal, feeding on small crustaceans (for example, Troglocaris shrimp, Niphargus , Asellus , and Synurella amphipods, and Oniscus asellus ), snails (for example, Belgrandiella ), and occasionally insects and insect larvae (for example, Trichoptera , Ephemeroptera , Plecoptera , and Diptera ). It does not chew its food, instead swallowing it whole. The olm

682-421: Is a behavioral adaptation to life underground. Reproduction has only been observed in captivity so far. 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

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744-442: 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. Postojna Cave is one of the birthplaces of biospeleology due to the olm and other rare cave inhabitants, such as the blind cave beetle . The image of the olm contributes significantly to the fame of Postojna Cave, which Slovenia successfully utilizes for

806-415: Is a type of salamander that primarily or exclusively inhabits caves , a group that includes several species. Some of these animals have developed special, even extreme, adaptations to their subterranean environments. Some species have only rudimentary (or even absent) eyes ( blind salamanders ). Others lack pigmentation, rendering them a pale yellowish or pinkish color (e.g., Eurycea rathbuni ). With

868-479: 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 receptors . Although blind, the olm swims away from light. The eyes are regressed, but retain sensitivity. They lie deep below

930-483: Is always pigmented and dark brownish to blackish when adult. The olm's pear-shaped head ends with a short, dorsoventrally flattened snout. The mouth opening is small, with tiny teeth forming a sieve to keep larger particles inside the mouth. The nostrils are so small as to be imperceptible, but are placed somewhat laterally near the end of the snout. The regressed eyes are covered by a layer of skin. The olm breathes with external gills that form two branched tufts at

992-436: Is around 68.5 years. When compared to the longevity and body mass of other amphibians, olms are outliers , living longer than would be predicted from their size. Olms from different cave systems differ substantially in body measurements, color, and some microscopic characteristics. Earlier researchers used these differences to support the division into five species, while modern herpetologists understand that external morphology

1054-428: Is called močeril (from * močerъ 'earthworm, damp creepy-crawly'; moča 'dampness'). The olm's body is snakelike , 20–30 cm (8–12 in) long, with some specimens reaching up to 40 centimetres (16 in), which makes them some of the largest cave-dwelling animals in the world. The average length is between 23 and 25 cm. Females grow larger than males, but otherwise the primary external difference between

1116-459: Is composed of three major types of cells : fibroblasts , macrophages , and mast cells . Apart from these cells, the dermis is also composed of matrix components such as collagen (which provides strength ), elastin (which provides elasticity ), and extrafibrillar matrix , an extracellular gel-like substance primarily composed of glycosaminoglycans (most notably hyaluronan ), proteoglycans , and glycoproteins . The papillary dermis

1178-462: Is evidence that a small number of olms were introduced to the United Kingdom in the 1940s, although it's highly likely that the animals perished shortly after being released. The olm was used by Charles Darwin in his seminal work On the Origin of Species as an example for the reduction of structures through disuse: Far from feeling surprise that some of the cave-animals should be very anomalous...as

1240-435: 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 between the various populations – individuals from Stična, Slovenia, have shorter heads on average than those from Tržič , Slovenia, and

1302-565: Is one of the leading groups studying the olm under the guidance of Boris Bulog . There are also several cave laboratories in Europe in which olms have been introduced and are being studied. These are Moulis, Ariège ( France ), Choranche cave ( France ), Han-sur-Lesse ( Belgium ), and Aggtelek ( Hungary ). They were also introduced into the Hermannshöhle ( Germany ) and Oliero ( Italy ) caves, where they still live today. Additionally, there

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1364-635: Is possible only for research purposes by permission of the National Administration for Nature and Environment Protection. As of 2020 the Croatian population has been assessed as ' critically endangered ' in Croatia. As of 1999, the environmental laws in Bosnia and Herzegovina and Montenegro had not yet been clarified for this species. In the 1980s the IUCN claimed that some illegal collection of this species for

1426-473: Is regulated by the hormone thyroxine , secreted 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 tissues to thyroxine. Longevity is estimated at up to 58 years. A study published in Biology Letters estimated that they have a maximum lifespan of over 100 years and that the lifespan of an average adult

1488-728: 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 lipids and glycogen in the liver . When food is scarce, it reduces its activity and 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. Olms are gregarious , and usually aggregate either under stones or in fissures. 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 . This

1550-462: 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. An olm (Proteus) genome project is currently underway by the University of Ljubljana and BGI . With an estimated genome size roughly 15-times

1612-601: Is the uppermost layer of the dermis. It intertwines with the rete ridges of the epidermis and is composed of fine and loosely arranged collagen fibers. The papillary region is composed of loose areolar connective tissue . It is named for its fingerlike projections called papillae or dermal papillae specifically, that extend toward the epidermis and contain either terminal networks of blood capillaries or tactile Meissner's corpuscles . The dermal papillae (DP) (singular papilla , diminutive of Latin papula , 'pimple') are small, nipple-like extensions (or interdigitations) of

1674-565: The European Union in 2004, 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, thus its capturing or killing is allowed only under specific circumstances determined by the local authorities (e.g. scientific study). In Croatia, the olm is protected by the legislation designed to protect amphibians – collecting

1736-561: The Istrian peninsula, for example. The black olm ( Proteus anguinus parkelj Sket & Arntzen, 1994 ) is the only recognized subspecies of the olm other than the nominate subspecies . It is endemic to the underground waters near Črnomelj , Slovenia, an area smaller than 100 square kilometres (39 sq mi). It was first found in 1986 by members of the Slovenian Karst Research Institute , who were exploring

1798-568: The Pleistocene layer. In his 1998 book, J. Alan Hollman described the species as a "problematic" taxon, saying that Brunner's drawing of the bone does not adequately show the differences between P. bavaricus and P. anguinus . The first written mention of the olm is in Johann Weikhard von Valvasor 's The Glory of the Duchy of Carniola (1689) as a baby dragon . Heavy rains of Slovenia would wash

1860-670: The axolotl and the mudpuppies ( Necturus ). The word olm is a German loanword that was incorporated into English in the late 19th century. The origin of the German Olm or Grottenolm 'cave olm', is unclear. It may be a variant of the word Molch 'salamander'. It is also called the "human fish" by locals because of its fleshy skin color (translated literally from Slovene : človeška ribica , Macedonian : човечка рипка , Croatian : čovječja ribica , Bosnian : čovječija ribica , Serbian : човечја рибица ), as well as "cave salamander" or "white salamander". In Slovenia, it

1922-417: The cutis ) and subcutaneous tissues , that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided into two layers, the superficial area adjacent to the epidermis called the papillary region and a deep thicker area known as the reticular dermis. The dermis is tightly connected to the epidermis through a basement membrane . Structural components of

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1984-473: The 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. 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

2046-489: 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. The female lays up to 70 eggs, each about 12 millimetres (0.5 in) in diameter, and places them between rocks, where they remain under her protection. The average is 35 eggs and the adult female typically breeds every 12.5 years. The tadpoles are 2 centimetres (0.8 in) long when they hatch and live on yolk stored in

2108-528: 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 pesticides , fertilizers , polychlorinated biphenyls (PCBs), which are or were used in

2170-456: The area of frequencies of sound waves between 10 and more than 12,000 Hz, while the greatest sensitivity is reached between 1,500 and 2,000 Hz.The ethological experiments indicate that the best hearing sensitivity of Proteus is between 10 Hz and up to 12,000 Hz. The lateral line supplements inner ear sensitivity by registering low-frequency nearby water displacements. A new type of electroreception sensory organ has been analyzed on

2232-442: The back of the head. They are red in color because the oxygen-rich blood shows through the non-pigmented skin. The olm also has rudimentary lungs , but their role in respiration is only accessory, except during hypoxic conditions. 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. The olm's sensory system

2294-476: The cells of the digestive tract for a month. At a temperature of 10 °C (50 °F), the olm's embryonic development (time in the eggs before hatching) is 140 days, but it is somewhat slower in colder water and faster in warmer, being as little as 86 days at 15 °C (59 °F). After hatching, it takes another 14 years to reach sexual maturity if living in water that is 10 °C (50 °F). The larvae gain adult appearance after nearly four months, with

2356-646: The century that Carl Franz Anton Ritter von Schreibers from the Naturhistorisches Museum of Vienna started to look into this animal's anatomy. The specimens were sent to him by Sigmund 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. A Dr Edwards

2418-482: The dermis are collagen , elastic fibers , and extrafibrillar matrix . It also contains mechanoreceptors that provide the sense of touch and thermoreceptors that provide the sense of heat . In addition, hair follicles , sweat glands , sebaceous glands (oil glands) , apocrine glands , lymphatic vessels , nerves and blood vessels are present in the dermis. Those blood vessels provide nourishment and waste removal for both dermal and epidermal cells. The dermis

2480-532: The dermis into the epidermis . At the surface of the skin in hands and feet, they appear as epidermal, papillary or friction ridges (colloquially known as fingerprints ). Blood vessels in the dermal papillae nourish all hair follicles and bring nutrients and oxygen to the lower layers of epidermal cells. The pattern of ridges produced in hands and feet are partly genetically determined features that are developed before birth. They remain substantially unaltered (except in size) throughout life, and therefore determine

2542-523: The duration of development strongly correlating with water temperature. Unconfirmed historical observations of viviparity 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. Paul Kammerer reported that female olm gave birth to live young in water at or below 13 °C (55 °F) and laid eggs at higher, but rigorous observations have not confirmed that. The olm appears to be exclusively oviparous . Development of

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2604-506: The head of Proteus , utilizing light and electron microscopy . These new organs have been described as ampullary organs . Like some other lower vertebrates , the olm has the ability to register weak electric fields . Some behavioral experiments suggest that the olm may be able to use Earth's magnetic field to orient itself. In 2002, Proteus anguinus was found to align itself with natural and artificially modified magnetic fields. The olm lives in well-oxygenated underground waters with

2666-413: The increase in the surface area prevents the dermal and epidermal layers from separating by strengthening the junction between them. With age, the papillae tend to flatten and sometimes increase in number. The skin of the hands and fingers and the feet and toes is known by forensic scientists as friction ridge skin. It is known by anatomists as thick skin, volar skin or hairless skin. It has raised ridges,

2728-415: 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 pigment riboflavin , making it yellowish-white or pink in color. The white skin color of the olm retains the ability to produce melanin , and will gradually turn dark when exposed to light; in some cases the larvae are also colored. One population, the black olm ,

2790-427: The notable exception of the olm ( Proteus anguinus ), all "cave salamanders" are members of the family Plethodontidae ("lungless salamanders"). Almost all of them are paedomorphic and therefore never undergo metamorphosis, but it is not clear if this happened before or after they adapted to an existence in caves, as some species that don't live in caves are also paedomorphic. The first dedicated scientific study of

2852-413: 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 . In other amphibians, the metamorphosis

2914-517: The olm were eventually included in the Slovenian, Italian and Croatian parts of the Natura 2000 network. 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

2976-458: The olms up from their subterranean habitat, giving rise to the folklore belief that great dragons lived beneath the Earth's crust, and the olms were the undeveloped offspring of these mythical beasts. In his book Valvasor compiled the local Slovenian folk stories and pieced together the rich mythology of the creature and documented observations of the olm as "Barely a span long, akin to a lizard, in short,

3038-401: The oral cavity are used for tasting food, where those near the gills probably sense chemicals in the surrounding water. The sensory epithelia of the inner ear are very specifically differentiated, enabling the olm to receive sound waves in the water, as well as vibrations from the ground. The complex functional-morphological orientation of the sensory cells enables the animal to register

3100-468: The patterns of fingerprints, making them useful in certain functions of personal identification. The dermal papillae are part of the uppermost layer of the dermis, the papillary dermis, and the ridges they form greatly increase the surface area between the dermis and epidermis. Because the main function of the dermis is to support the epidermis, this greatly increases the exchange of oxygen, nutrients, and waste products between these two layers. Additionally,

3162-477: The pet trade took place, but that the extent of this was unknown: this text has been copied into subsequent assessments, but by now the anecdotic claims are not considered to be indicative of a major threat. Since the 1980s until the most recent assessment in 2022 the organisation has rated the conservation status for the IUCN Red List as ' vulnerable ', this because of its natural distribution being fragmented over

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3224-430: The physiological processes. Behavioral experiments revealed that the skin itself is also sensitive to light. Photosensitivity of the integument is due to the pigment melanopsin inside specialized cells called melanophores . Preliminary immunocytochemical analyses support the existence of photosensitive pigment also in the animal's integument. The olm is capable of sensing very low concentrations of organic compounds in

3286-616: The promotion of ecotourism in Postojna and other parts of Slovenian karst. Tours of Postojna Cave also include a tour around the speleobiological station – the Proteus vivarium , showing different aspects of the cave environment. The olm was also depicted on one of the Slovenian tolar coins. It was also the namesake of Proteus , the oldest Slovenian popular science magazine, first published in 1933. Cave salamander A cave salamander

3348-399: The sexes is in the cloaca region (shape and size) when breeding. 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

3410-432: The size of human genome, this will likely be the largest animal genome sequenced so far. 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. The contamination of the karst underground waters is due to the large number of waste disposal sites leached by rainwater, as well as to

3472-567: The sound sources. 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. Behavioural (ethological) tests have shown that its sensitivity for detecting underwater sound waves reaches into

3534-430: The superficial epithelium. Dermal papillae are less pronounced in thin skin areas. The reticular dermis is the lower layer of the dermis, found under the papillary dermis, composed of dense irregular connective tissue featuring densely-packed collagen fibers. It is the primary location of dermal elastic fibers. The reticular region is usually much thicker than the overlying papillary dermis. It receives its name from

3596-544: The water from Dobličica karst spring in the White Carniola region. It has several features separating it from the nominotypical subspecies ( Proteus a. anguinus ): A potential species, Proteus bavaricus , is speculated to be closely related to P. anguinus . The species was described from a single bone by George Brunner, and the holotype is housed in his private collection. It was found in Bavaria 's Devil's Cave , in

3658-460: The water. They are better at sensing both the quantity and quality of prey by smell than related amphibians. The nasal epithelium , located on the inner surface of the nasal cavity and in the Jacobson's organ , is thicker than in other amphibians. 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

3720-599: Was included in annexes II and IV of the 1992 EU Habitats Directive (92/43/EEC). The list of species in annex II, combined with the habitats listed in annex I, is used by individual countries to designate protected areas known as 'Special Areas of Conservation'. These areas, combined with others created by the older Birds Directive were to form the Natura 2000 network. Annex IV additionally lists "animal and plant species of community interest in need of strict protection", although this has little legal ramifications. Areas inhabited by

3782-407: Was known to the locals as a "cave puppet" and is now known to be Eurycea lucifuga . His discovery was not surprising at the time because E. lucifuga lives near the entrance of caves, making an in-depth exploration unnecessary. Additionally, E. lucifuga is neither blind nor depigmented. Dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up

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3844-490: Was quoted in a book of 1839 as believing that "...the Proteus Anguinis is the first stage of an animal prevented from growing to perfection by inhabiting the subterraneous waters of Carniola." In 1880 Marie von Chauvin began the first long-term study of olms in captivity. She learned that they detected prey's motion, panicked when a heavy object was dropped near their habitat, and developed color if exposed to weak light for

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