Olm
Encyclopedia
The olm, or proteus (Proteus anguinus), is a blind amphibian
endemic to the subterranean waters of caves of the Dinaric
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
Proteidae, and the only European exclusively cave-dwelling
chordate
. It is also occasionally called the "human fish" by locals because of its skin color, similar to that of white people
(translated literally from and ), as well as "cave salamander
" or "white salamander." In Slovenia it is also known by the name močeril, which translates as "the one that burrows into wetness."
This animal is most notable for its adaptations to a life of complete darkness in its underground habitat. The olm's eye
s are undeveloped, leaving it blind, while its other sense
s, particularly those of smell
and hearing
, are acutely developed. It also lacks any pigmentation
in its skin
. In contrast to most amphibians, the olm is entirely aquatic
, and it eats, sleeps, and breeds underwater. It has 3 toes on its forelimbs, but 2 toes on its hind feet. It also exhibits neoteny
, retaining larva
l characteristics like external gill
s into adulthood, like the American amphibians, the axolotl
and the mud puppy.
like, 20–30 cm (8–12 in) long, with some specimens reaching up to 40 centimetres (16 in). 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 pigment
riboflavin
, making it yellowish-white or pink in color. The internal organs can be seen shining through on the abdominal part of the body. The resemblance in color to that of white
humans 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 larva
e are also colored. Its 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 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. 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.
s.
. They lie deep below 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 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 analysis support the existence of photosensitive pigment also in the animal's integument
, 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 the oral cavity are used for tasting food, where those near the gills probably sense chemicals in the surrounding water.
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
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. 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 organs.
Like some other lower vertebrate
s, the olm has the ability to register weak electric field
s. 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.
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. 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. 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 oviparous.
The female lays up to 70 eggs, each about 12 millimetre (0.47244094488189 in) in diameter, and places them between rocks, where they remain under her protection. The tadpoles are 2 centimetre (0.78740157480315 in) long when they hatch and live on yolk stored in the cells of the digestive tract for a month.
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
. 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 tissues
to thyroxine.
The olm swims by eel-like twisting of its body, assisted only slightly by its poorly developed legs. It is a predatory animal, feeding on small crab
s, snail
s and occasionally insect
s. 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 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 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 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.
Longevity is estimated at up to 58 years. Individual specimens have been kept under semi-natural conditions in concrete basins for up to 70 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 is around 68.5 years. When compared to the longevity and body mass of other amphibians, olms are outlier
s, living longer than would be predicted from their size.
. 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.
, 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 the water from Dobličice karst spring in the Bela krajina
region.
It has several features separating it from the type subspecies
:
These features suggest that the Black Proteus has probably colonized underground habitats more recently and still retains some nontroglomorphic characteristics.
s with wing
s, which could represent gills, in a relief
on a Venetian 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
. Heavy rains of Slovenia would wash 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 The Glory of the Duchy of Carniola
, 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, 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
, G.A. Scopoli
; he 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 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 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 later, 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. 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
into the Hermannshöhle (Germany
) and Oliero (Italy
) caves, where they still live today.
The olm was used by Charles Darwin
in his famous On the Origin of Species as an example for the reduction of structures through disuse:
s, fertilizer
s, polychlorinated biphenyls (PCBs), 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). 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. 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 – 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.
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 speleobiology 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 the Postojna cave, which Slovenia successfully utilizes for the promotion of ecotourism
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.
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.
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
endemic to the subterranean waters of caves of the Dinaric
Dinaric Alps
The Dinaric Alps or Dinarides form a mountain chain in Southern Europe, spanning areas of Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Kosovo, Albania and Montenegro....
karst
Karst topography
Karst topography is a geologic formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite, but has also been documented for weathering resistant rocks like quartzite given the right conditions.Due to subterranean drainage, there...
of southern Europe. It lives in the waters that flow underground through this extensive limestone region including waters of the Soča
Soca
The Soča or Isonzo is a 140 km long river that flows through western Slovenia and northeastern Italy. An Alpine river in character, its source lies in the Trenta Valley in the Julian Alps in Slovenia, at an elevation of around 1,100 metres...
river basin near Trieste
Trieste
Trieste is a city and seaport in northeastern Italy. It is situated towards the end of a narrow strip of land lying between the Adriatic Sea and Italy's border with Slovenia, which lies almost immediately south and east of the city...
in Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, through to southern Slovenia
Slovenia
Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...
, southwestern Croatia
Croatia
Croatia , officially the Republic of Croatia , is a unitary democratic parliamentary republic in Europe at the crossroads of the Mitteleuropa, the Balkans, and the Mediterranean. Its capital and largest city is Zagreb. The country is divided into 20 counties and the city of Zagreb. Croatia covers ...
, and Herzegovina
Herzegovina
Herzegovina is the southern region of Bosnia and Herzegovina. While there is no official border distinguishing it from the Bosnian region, it is generally accepted that the borders of the region are Croatia to the west, Montenegro to the south, the canton boundaries of the Herzegovina-Neretva...
. The olm is the only species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in its genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Proteus, the only Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
an species of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Proteidae, and the only European exclusively cave-dwelling
Troglobite
Troglobites are small cave-dwelling animals that have adapted to their dark surroundings. Troglobite species include spiders, insects, fish and others. They live permanently underground and cannot survive outside the cave environment. Troglobite adaptations and characteristics include a heightened...
chordate
Chordate
Chordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail...
. It is also occasionally called the "human fish" by locals because of its skin color, similar to that of white people
White people
White people is a term which usually refers to human beings characterized, at least in part, by the light pigmentation of their skin...
(translated literally from and ), as well as "cave salamander
Salamander
Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...
" or "white salamander." In Slovenia it is also known by the name močeril, which translates as "the one that burrows into wetness."
This animal is most notable for its adaptations to a life of complete darkness in its underground habitat. The olm's eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s are undeveloped, leaving it blind, while its other sense
Sense
Senses are physiological capacities of organisms that provide inputs for perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology , and philosophy of perception...
s, particularly those of smell
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
and hearing
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
, are acutely developed. It also lacks any pigmentation
Biological pigment
Biological pigments, also known simply as pigments or biochromes are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments...
in its skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
. In contrast to most amphibians, the olm is entirely aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
, and it eats, sleeps, and breeds underwater. It has 3 toes on its forelimbs, but 2 toes on its hind feet. It also exhibits neoteny
Neoteny
Neoteny , also called juvenilization , is one of the two ways by which paedomorphism can arise. Paedomorphism is the retention by adults of traits previously seen only in juveniles, and is a subject studied in the field of developmental biology. In neoteny, the physiological development of an...
, retaining larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
l characteristics like external gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s into adulthood, like the American amphibians, the axolotl
Axolotl
The axolotl , Ambystoma mexicanum, is a neotenic salamander, closely related to the Tiger Salamander. Larvae of this species fail to undergo metamorphosis, so the adults remain aquatic and gilled. It is also called ajolote...
and the mud puppy.
External appearance
The olm's body is snakeSnake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
like, 20–30 cm (8–12 in) long, with some specimens reaching up to 40 centimetres (16 in). The trunk is cylindrical, uniformly thick, and segmented with regularly spaced furrows at the myomere
Myomere
Myomere are the blocks of skeletal muscle tissue found commonly in chordates. They are commonly zig-zag, "W" or "V"-shaped muscle fibers. The myomeres are separated from adjacent myomere by connective tissues and most easily seen in larval fishes or in the olm...
borders. The tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...
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 pigment
Biological pigment
Biological pigments, also known simply as pigments or biochromes are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments...
riboflavin
Riboflavin
Riboflavin, also known as vitamin B2 or additive E101, is an easily absorbed micronutrient with a key role in maintaining health in humans and animals. It is the central component of the cofactors FAD and FMN, and is therefore required by all flavoproteins. As such, vitamin B2 is required for a...
, making it yellowish-white or pink in color. The internal organs can be seen shining through on the abdominal part of the body. The resemblance in color to that of white
White people
White people is a term which usually refers to human beings characterized, at least in part, by the light pigmentation of their skin...
humans is the reason why the Proteus is called human fish in some languages. However, the olm's skin retains the ability to produce melanin
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...
. When exposed to light, it will gradually turn dark, and in some cases the larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e are also colored. Its pear-shaped head ends with a short, dorsoventrally flattened snout. The mouth opening is small, with tiny teeth
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
forming a sieve
Sieve
A sieve, or sifter, separates wanted elements from unwanted material using a woven screen such as a mesh or net. However, in cooking, especially with flour, a sifter is used to aerate the substance, among other things. A strainer is a type of sieve typically used to separate a solid from a liquid...
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 eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s are covered by a layer of skin. The olm breathes with external gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s that form two branched tufts at the back of the head. They are red in color because the oxygen-rich blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
shows through the non-pigmented skin. The olm also has rudimentary lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s, but their role in respiration is only accessory. The sexes are very similar in appearance, with males having a somewhat thicker cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
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. 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 receptorSensory receptor
In a sensory system, a sensory receptor is a sensory nerve ending that responds to a stimulus in the internal or external environment of an organism...
s.
Photoreceptors
The eyes are regressed, but retain sensitivity to lightLight
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
. They lie deep below 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 the physiological processes. Behavioral
Ethology
Ethology is the scientific study of animal behavior, and a sub-topic of zoology....
experiments revealed that the skin itself is also sensitive to light. Photosensitivity of the integument is due to the pigment melanopsin
Melanopsin
Melanopsin is a photopigment found in specialized photosensitive ganglion cells of the retina that are involved in the regulation of circadian rhythms, pupillary light reflex, and other non-visual responses to light. In structure, melanopsin is an opsin, a retinylidene protein variety of...
inside specialized cells called melanophores. Preliminary immunocytochemical analysis support the existence of photosensitive pigment also in the animal's integument
Chemoreceptors
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. The nasal epitheliumEpithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
, 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
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
epithelium of the mouth, most of them on the upper side of the tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
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 chemicals in the surrounding water.
Mechano- and electroreceptors
The sensory epithelia of the inner earInner ear
The inner ear is the innermost part of the vertebrate ear. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:...
are very specifically differentiated, enabling the olm to receive sound
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
waves in the water, as well as vibration
Vibration
Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...
s from the ground. The complex functional-morphological orientation of the sensory cells enables the animal to register the sound sources
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. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
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 organs.
Like some other lower vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s, the olm has the ability to register weak electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
s. Some behavioral experiments suggest that the olm may be able to use Earth's magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
to orient itself. Recently, Proteus anguinus has been found to align itself with natural and artificially modified magnetic fields.
Ecology and life history
The olm's embryoEmbryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
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. Unconfirmed historical observations of vivipary
Vivipary
Vivipary has two different meanings. In animals, it means development of the embryo inside the body of the mother, eventually leading to live birth, as opposed to laying eggs...
exist, but it has been shown that the females possess a gland
Gland
A gland is an organ in an animal's body that synthesizes a substance for release of substances such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface .- Types :...
that produces the egg casing, similar to those of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and egg-laying amphibians. 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 oviparous.
The female lays up to 70 eggs, each about 12 millimetre (0.47244094488189 in) in diameter, and places them between rocks, where they remain under her protection. The tadpoles are 2 centimetre (0.78740157480315 in) long when they hatch and live on yolk stored in the cells of the digestive tract for a month.
Development of the olm and other troglobite
Troglobite
Troglobites are small cave-dwelling animals that have adapted to their dark surroundings. Troglobite species include spiders, insects, fish and others. They live permanently underground and cannot survive outside the cave environment. Troglobite adaptations and characteristics include a heightened...
amphibians is characterized by heterochrony
Heterochrony
In biology, heterochrony is defined as a developmental change in the timing of events, leading to changes in size and shape. There are two main components, namely the onset and offset of a particular process, and the rate at which the process operates...
– the animal does not undergo metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
and instead retains larval features. The form of heterochrony in the olm is neoteny
Neoteny
Neoteny , also called juvenilization , is one of the two ways by which paedomorphism can arise. Paedomorphism is the retention by adults of traits previously seen only in juveniles, and is a subject studied in the field of developmental biology. In neoteny, the physiological development of an...
– delayed somatic
Somatic
The term somatic means 'of the body',, relating to the body. In medicine, somatic illness is bodily, not mental, illness. The term is often used in biology to refer to the cells of the body in contrast to the germ line cells which usually give rise to the gametes...
maturity with precocious reproductive maturity, i.e. reproductive maturity is reached while retaining the larval external morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
. In other amphibians, the metamorphosis is regulated by the hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
thyroxine
Thyroxine
Thyroxine, or 3,5,3',5'-tetraiodothyronine , a form of thyroid hormones, is the major hormone secreted by the follicular cells of the thyroid gland.-Synthesis and regulation:...
, excreted by the thyroid
Thyroid
The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage...
gland. The thyroid is normally developed and functioning in the olm, so the lack of metamorphosis is due to the unresponsiveness of key tissues
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
to thyroxine.
The olm swims by eel-like twisting of its body, assisted only slightly by its poorly developed legs. It is a predatory animal, feeding on small crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s, snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s and occasionally insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s. 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
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
s and glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...
in the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
. When food is scarce, it reduces its activity and metabolic rate
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
, 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
Social animal
A social animal is a loosely defined term for an organism that is highly interactive with other members of its species to the point of having a recognizable and distinct society.All mammals are social to the extent that mothers and offspring bond...
, 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
Display (zoology)
Display is a form of animal behaviour, linked to survival of the species in various ways. One example of display used by some species can be found in the form of courtship, with the male usually having a striking feature that is distinguished by colour, shape or size, used to attract a female...
. This 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 a female-attracting pheromone
Pheromone
A pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
. 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
Spermatophore
A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...
, 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
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
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.
Longevity is estimated at up to 58 years. Individual specimens have been kept under semi-natural conditions in concrete basins for up to 70 years. A study published in Biology Letters
Biology Letters
Biology Letters is a peer-reviewed scientific journal. It was split off as a separate journal from the Philosophical Transactions of the Royal Society B: Biological Sciences in 2005 after having been published as a supplement. Originally it was published quarterly, but from 2007 it has been...
estimated that they have a maximum lifespan of over 100 years and that the lifespan of an average adult is around 68.5 years. When compared to the longevity and body mass of other amphibians, olms are outlier
Outlier
In statistics, an outlier is an observation that is numerically distant from the rest of the data. Grubbs defined an outlier as: An outlying observation, or outlier, is one that appears to deviate markedly from other members of the sample in which it occurs....
s, living longer than would be predicted from their size.
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 populationPopulation
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
. 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
Tržic
Tržič is a town and municipality in northern Slovenia near the Austrian border . The first settlement was founded near the road that connected Roman city of Emona with Virunum in present-day Carinthia...
, Slovenia, and the Istria
Istria
Istria , formerly Histria , is the largest peninsula in the Adriatic Sea. The peninsula is located at the head of the Adriatic between the Gulf of Trieste and the Bay of Kvarner...
n peninsula, for example.
Black Proteus
The Black Proteus (Proteus anguinus parkelj Sket & Arntzen, 1994) is the only recognized subspecies of the olm, endemic to the underground waters near ČrnomeljCrnomelj
Črnomelj is a town and municipality in southeastern Slovenia. It lies on the left bank of the Lahinja and Dobličica rivers. The municipality is at the heart of the area of White Carniola, the southeastern part of the traditional region of Lower Carniola...
, 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 the water from Dobličice karst spring in the Bela krajina
White Carniola
White Carniola is a traditional region in southeastern Slovenia on the border with Croatia and is the most southern part of the historical and traditional region of Lower Carniola. Its major towns are Metlika, Črnomelj, and Semič, and the principal river is the Kolpa, which also forms part of the...
region.
It has several features separating it from the type subspecies
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
:
| Feature | Proteus anguinus anguinus | Proteus anguinus parkelj | Notes |
|---|---|---|---|
| Skin | Not pigmented. | Normally pigmented, dark brown, or black in color. | The most obvious difference. |
| Head shape | Long, slender. | Shorter, equally thick. Stronger jaw muscles visible as two bulbs on the top of the head. | |
| Body length | Shorter, 29–32 vertebrae. | Longer, 34–35 vertebrae. | Amphibians do not have a fixed number of vertebrae. |
| Appendages | Longer. | Shorter. | |
| Tail | Longer in proportion to the rest of the body. | Shorter in proportion. | |
| Eyes | Regressed. | Almost normally developed, although still small compared to other amphibians. Covered by a thin layer of transparent skin, no eyelids. | 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. |
| Other senses | Specific and highly sensitive. | Some sensory organs, particularly electroreceptors, less sensitive. | Not very obvious. |
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 snakeSnake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s with wing
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...
s, which could represent gills, in a relief
Relief
Relief is a sculptural technique. The term relief is from the Latin verb levo, to raise. To create a sculpture in relief is thus to give the impression that the sculpted material has been raised above the background plane...
on a Venetian stone fountain, probably originating from Karst.
The first written mention of the olm is in Janez Vajkard Valvasor
Janez Vajkard Valvasor
Johann Weichard Freiherr von Valvasor or simply Valvasor was a Slovenian nobleman, scientist and polymath, and a fellow of the Royal Society in London.-Biography:...
's The Glory of the Duchy of Carniola
The Glory of the Duchy of Carniola
The Glory of the Duchy of Carniola is Johann Weikhard von Valvasor's most important work on history and natural history of his homeland Carniola, a central part of the present-day Slovenia and Istria in Croatia....
(1689) as a baby dragon
Dragon
A dragon is a legendary creature, typically with serpentine or reptilian traits, that feature in the myths of many cultures. There are two distinct cultural traditions of dragons: the European dragon, derived from European folk traditions and ultimately related to Greek and Middle Eastern...
. Heavy rains of Slovenia would wash 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 The Glory of the Duchy of Carniola
The Glory of the Duchy of Carniola
The Glory of the Duchy of Carniola is Johann Weikhard von Valvasor's most important work on history and natural history of his homeland Carniola, a central part of the present-day Slovenia and Istria in Croatia....
, 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, a worm and vermin of which there are many hereabouts”.
The first researcher to retrieve a live olm was a physician
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...
and researcher from Idrija
Idrija
Idrija is a small town and municipality in the Goriška region of Slovenia. It is known for its mercury mine and lace....
, G.A. Scopoli
Giovanni Antonio Scopoli
Giovanni Antonio Scopoli was an Italian physician and naturalist.-Biography:...
; he sent dead specimens and drawings to colleagues and collectors. Josephus Nicolaus Laurenti
Josephus Nicolaus Laurenti
Josephus Nicolaus Laurenti was an Austrian naturalist of Italian origin.Laurenti is considered the auctor of the class Reptilia through his authorship of on the poisonous function of reptiles and amphibians...
, 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
Carl Franz Anton Ritter von Schreibers
Carl Franz Anton Ritter von Schreibers was an Austrian naturalist who was a native of Pressburg, Hungary, Habsburg Empire . He earned his medical doctorate from Vienna in 1798, but also studied botany, mineralogy and zoology at the university...
from the Naturhistorisches Museum
Naturhistorisches Museum
The Naturhistorisches Museum Wien or NHMW is a large museum located in Vienna, Austria.The collections displayed cover , and the museum has a website providing an overview as a video virtual tour....
of Vienna
Vienna
Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...
started to look into this animal's anatomy. The specimens were sent to him by Žiga Zois. Schreibers presented his findings in 1801 to The Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...
in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, and later also in Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
. 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 later, the Research Group for functional morphological Studies of the Vertebrates in the Department of Biology (Biotechnical Faculty, University of Ljubljana
University of Ljubljana
The University of Ljubljana is the oldest and largest university in Slovenia. With 64,000 enrolled graduate and postgraduate students, it is among the largest universities in Europe.-Beginnings:...
), is one of the leading groups studying the olm under the guidance of Prof.dr. Boris Bulog. There are also several cave laboratories in Europe, where olms have been introduced and are being studied. These are Moulis
Moulis
-Places:* Moulis, a French commune in the department of Ariège ;* Moulis, Tarn-et-Garonne, an ancient French commune in Tarn-et-Garonne, today part of Reyniès* Moulis-en-Médoc French commune in the department of Gironde.-People:...
(France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
), Kent's Cavern
Kent's Cavern
Kents Cavern is a cave system in Torquay, Devon, England. It is notable for its archaeological and geological features. The caves are a geological Site of Special Scientific Interest and a Scheduled Ancient Monument , and are open to the public.-Prehistory:The caverns and passages at the site were...
(England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
), Han-sur-Lesse
Caves of Han-sur-Lesse
The Caves of Han-sur-Lesse are a major Belgian tourist attraction located on the outskirts of the village of Han-sur-Lesse....
(Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
) and Aggtelek
Aggtelek (town)
Aggtelek is a village in the county of Borsod-Abaúj-Zemplén, Hungary. It is known for the vast stalactite caverns of the nearby Baradla-Domica cave system, part of the UNESCO World Heritage Site of Aggtelek and Slovak Karst....
(Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
). They were also introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
into the Hermannshöhle (Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
) and Oliero (Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
) caves, where they still live today.
The olm was used by Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
in his famous On the Origin of Species as an example for the reduction of structures through disuse:
Conservation status
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 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 pesticidePesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
s, fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s, polychlorinated biphenyls (PCBs), 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). Appendix II seeks to preserve favorable conservation status in animal and plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
species along with their habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s by protecting the species or defining special areas of conservation. These areas of conservation form the Natura 2000
Natura 2000
Natura 2000 is an ecological network of protected areas in the territory of the European Union.-Origins:In May 1992, the governments of the European Communities adopted legislation designed to protect the most seriously threatened habitats and species across Europe. This legislation is called the...
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
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...
, 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. The Postojna
Postojna
Postojna is a town and a municipality in the traditional region of Inner Carniola, from Trieste, in southwestern Slovenia. Population 14,581 .-History:...
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 – collecting is possible only for research purposes by permission of the National Administration for Nature and Environment Protection. Conservation status in Bosnia and Herzegovina
Bosnia and Herzegovina
Bosnia and Herzegovina , sometimes called Bosnia-Herzegovina or simply Bosnia, is a country in Southern Europe, on the Balkan Peninsula. Bordered by Croatia to the north, west and south, Serbia to the east, and Montenegro to the southeast, Bosnia and Herzegovina is almost landlocked, except for the...
and Montenegro
Montenegro
Montenegro Montenegrin: Crna Gora Црна Гора , meaning "Black Mountain") is a country located in Southeastern Europe. It has a coast on the Adriatic Sea to the south-west and is bordered by Croatia to the west, Bosnia and Herzegovina to the northwest, Serbia to the northeast and Albania to the...
has not yet been defined.
On the IUCN Red List
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
, the olm is listed as vulnerable because of its fragmented and limited distribution and ever-decreasing population.
Cultural significance
Postojna Cave
Postojna Cave is a 20,570 m long Karst cave system near Postojna, Slovenia. It is the longest cave system in the country as well as one of its top tourism sites.-History:The caves were created by the Pivka River....
is one of the birthplaces of speleobiology due to the olm and other rare cave inhabitants, such as the blind cave beetle
Leptodirus hochenwartii
Leptodirus hochenwartii, or L. hohenwarti, is a cave beetle in the family Leiodidae and the only species in the genus Leptodirus. It is a true troglobite, adapted to the life underground and unable to survive outside. Its distinguishing features are slender thorax, elongated legs and antennae, the...
. The image of the olm contributes significantly to the fame of the Postojna cave, which Slovenia successfully utilizes for the promotion of ecotourism
Ecotourism
Ecotourism is a form of tourism visiting fragile, pristine, and usually protected areas, intended as a low impact and often small scale alternative to standard commercial tourism...
in Postojna
Postojna
Postojna is a town and a municipality in the traditional region of Inner Carniola, from Trieste, in southwestern Slovenia. Population 14,581 .-History:...
and other parts of Slovenian karst. Tours of the Postojna cave also include a tour around the speleobiological station – the Proteus vivarium
Vivarium
A vivarium is a usually enclosed area for keeping and raising animals or plants for observation or research...
, showing different aspects of the cave environment.
The olm was also depicted on one of the Slovenian tolar
Slovenian tolar
The tolar was the currency of Slovenia from 1991 until the introduction of the euro on 1 January 2007. It was subdivided into 100 stotins...
coins, and was the namesake of Proteus, the oldest Slovenian popular science magazine, first published in 1933.
External links
- EDGE of Existence Olm information
- AmphibiaWeb page for the olm
- Flora and Fauna of Caves: Proteus anguinus Proteus magazine
- Slovenian practice example: Human Fish (Proteus anguinus)
- The olm on ARKive – pictures, films The olm on the pages of the Slovenian Natural history museum.
- The Global Amphibian Assessment - Proteus anguinus
- Istria on the Internet, Fauna - Proteus anguinus