Elongate and slender salamander with small, thin extremities. The front legs bear three toes, the rear legs two toes. The flattened tail is markedly shorter than the trunk. The head is elongated with a rounded snout. Eyes are poorly developed and covered by skin in the nominate subspecies. There are three pink external gills on each side of the head. The translucent skin also shows the contours of the internal organs on the ventral site of the body, making it easy to determine the sex of adults. Juveniles sometimes show a faded spotting. Dark pigmentation can be induced by exposure to light. This shows that these animals do not display albinism, as commonly thought, because they still possess the ability to produce melanin. The variant previously described as a subspecies (P. anguinus parkelj, the black olm, now shown to be phylogenetically nested well within P. anguinus; see Comments) has a permanent dark pigmentation of the skin, and probably functional eyes. It also has a shorter head than P. a. anguinus.
The average total length lies between 23-25 cm. They may grow up to 30 cm and rarely more than 30 cm. Black Proteus can grow up to 40 cm or more. Males are somewhat smaller than females. Other sexually dimorphic characteristics include the shape and size of the cloaca during breeding activity, with the males having a larger and more elongated swollen cloaca than the females.
Sket and Arntzen (1994) described black populations of Proteus as a separates subspecies, and defended this taxonomic decision based on the limited amount of morphological (morphometric) differentiation that Arntzen and Sket (1997) observed between the two subspecies. However, Goricki and Tronteltj (2006) found little differentiation between the two subspecies at the molecular level and questioned whether the designation of subspecies was appropriate. Subsequently Tronteltj et al. (2007) reported that both "subspecies" were nested within a southeastern Slovenian clade of P. anguinus and that the division was in fact simply intra-lineage diversity.
Proteus is the only cave-adapted vertebrate in Europe. Current genetic research under the direction of Dr. Boris Sket of the University of Ljubljana suggests that Proteus anguinus is actually a complex of several species, with phylogenetic analysis revealing six cryptic lineages (see Trontelj et al. 2007).
Functional-morphological and environmental studies of Proteus have been performed at the Department of Biology, Biotechnical Faculty (BF), University of Ljubljana, Slovenia for more than thirty years, with the most recent twenty years under the guidance of Prof. dr. Boris Bulog.
- Arntzen, J. W., and Sket, B. (1997). ''Morphometric analysis of black and white European cave salamanders, Proteus anguinus.'' Journal of Zoology (London), 241(4), 699-707.
- Bizjak-Mali, L. (1995). Histological, histochemical and ultrastructural analysis of the digestive tract of Proteus anguinus (Amphibia, Caudata), Master of Science Thesis. University of Ljubljana, Biotechnical Faculty, Department of Biology, Slovenia.
- Bizjak-Mali, L. and Bulog, B. (2004). ''Histology and ultrastructure of the gut epithelium of the neotenic cave salamander, Proteus anguinus (Amphibia, Caudata).'' Journal of Mophology, 259, 82-89.
- Boehme, W., Grossenbacher, K., and Thiesmeier, B. (1999). Handbuch der Reptilien und Amphibien Europas, band 4/I:Schwanzlurche (Urodela). Aula-Verlag, Wiesbaden.
- Bons, J. and Beniez, P. (1996). Amphibiens et Reptiles du Maroc (Sahara occidental compris). Asociacion Herpetologica EspaÃ±ola, Barcelona.
- Bulog B. (1989). ''Differentiation of the inner ear sensory epithelia of Proteus anguinus (Urodela, Amphibia).'' Journal of Morphology, 202, 325-338.
- Bulog B. et al. (2003). Black Proteus: mysterious dweller of the Karst in Bela krajina . Ljubljana: TV Slovenia, Video tape
- Bulog B., and Schlegel, P. (2000). ''Functional morphology of the inner ear and underwater audiograms of Proteus anguinus (Amphibia, Urodela).'' PflÃ¼gers Archive, 439(3), 165-167.
- Bulog, B., Mihajl, K., Jeran, Z., and Toman, M. (2002). ''Trace element concentrations in the tissues of Proteus anguinus (Amphibia, Caudata) and the surrounding environment.'' Water, Air, and Soil Pollution, 136(1-4), 147-163.
- Dumas, P. and Chris, B. (1998). ''The olfaction in Proteus anguinus.'' Behavioural Processes, 43, 107-113.
- Durand, J.P. (1976). ''Ocular development and involution in the European Cave Salamander, Proteus anguinus Laurenti.'' The Biologial Bulletin, 151(3), 450-466.
- Gasc, J.-P. (1997). Atlas of Amphibians and Reptiles in Europe. Societas Europaea Herpetologica, Bonn, Germany.
- Gorički, S., and Trontelj, P. (2006). ''Structure and evolution of the mitochondrial control region and flanking sequences in the European cave salamander Proteus anguinus.'' Gene, 378, 31-41.
- Griffiths, R.A. (1996). Newts and Salamanders of Europe. T. and A. D. Poyser, London.
- Guillaume, O. (2000). ''Role of chemical communication and behavioral interactions among conspecifics in the choice of shelters by the cave-dwelling salamander Proteus anguinus (Caudata, Proteidae).'' Canadian Journal of Zoology, 78(2), 167-173.
- Honegger, R. E. (1981). Threatened Amphibians and Reptiles in Europe. Akademische Verlagsgesellschaft, Wiesbaden.
- Istenič, L. and Bulog, B. (1979). ''The structural differentiations of the buccal and pharyngeal mucous membrane of the Proteus anguinus Laur.'' BioloÅ¡ki Vestnik, 27, 1-12.
- Istenič, L. and Bulog, B. (1984). ''Some evidence for the ampullary organs in the European cave salamander Proteus anguinus (Urodela, Amphibia).'' Cell and Tissue Research, 235, 393-402.
- Istenič, L. and Sojar, A. (1974). ''Oxygen consumption of Proteus anguinus.'' Acta Carsologica, 6, 299-305.
- Istenic, L. and Ziegler, I. (1974). ''Riboflavin as ''pigment'' in the skin of Proteus anguinus L.'' Naturwissenschaften, 12, 686-687.
- Kalezic, M., and Dzukic, G. (2001). ''Amphibian status in Serbia and Montenegro (FR Yugoslavia).'' FROGLOG, 45.
- Kos, M. (1992). ''Fine structure of of the skin of Proteus anguinus Laurenti (Urodela, Amphibia) and comparison of the skin of the pigmentless and pigmented specimen. Unpublished dissertation.''
- Kos, M., Bulog, B., SzÃ©l, A., and RÃ¶hlich P. (2001). ''Immunocytochemical demonstration of visualpigments in the degenerate retinal and pineal photoreceptors of the blind cavesalamander (Proteus anguinus).'' Cell and Tissue Research, 303(1), 15-25.
- NÃ¶llert, A. and NÃ¶llert, C. (1992). Die Amphibien Europas. Franckh-Kosmos Verlags-GmbH and Company, Stuttgart.
- Schegel, P., and Bulog, B. (1997). ''Population-specific behavioral electrosensitivity of the European blind cave salamander, Proteus anguinus.'' Journal of Physiology (Paris), 91, 75-79.
- Schlegel P. (1996). ''Behavioral evidence and possible physical and physiological mechanisms for earth magnetic orientation in the European Blind Cave Salamander, Proteus anguinus.'' MÃ©moires de BiospÃ©ologie, 23, 5-16.
- Schlegel P.A., Briegleb W., Bulog B., Steinfartz S. (2006). ''Revue et nouvellesdonnÃ©es sur la sensitivitÃ© a la lumiere et orientation non-visuelle chez Proteus anguinus, Calotriton asper et Desmognathus ochrophaeus (Amphibiens urodeles hypogÃ©s).'' Bulletin de la SociÃ©tÃ© herpÃ©tologique de France, 118, 1-31.
- Sket, B. (1997). ''Distribution of Proteus (Amphibia: Urodela: Proteidae) and its possible explanation.'' Journal of Biogeography, 24, 263-280.
- Stet, B., and Arntzen, J. W. (1994). ''A black, non-troglomorphic amphibian from the karst of Slovenia: Proteus anguinus parkelj n. ssp. (Urodela: Proteidae).'' Bijdragen tot de Dierkunde, 64(1), 33-53.
- Stuart, S., Hoffmann, M., Chanson, J., Cox, N., Berridge, R., Ramani, P., and Young, B. (eds) (2008). Threatened Amphibians of the World. Lynx Edicions, IUCN, and Conservation International, Barcelona, Spain; Gland, Switzerland; and Arlington, Virginia, USA.
- Stumpel-Rieks, S. E. (1992). Nomina Herpetofaunae Europaeae. AULA-Verlag, Wiesbaden.
- Trontelj, P., Douady, C., FiÅ¡er, C., Gibert, J., Gorički, S., LefÃ©bure, T., Sket, B., and ZakÅ¡ek, V. (2007). ''A molecular test for cryptic diversity in ground water: how large are the ranges of macro-stygobionts?'' Freshwater Biology, 54, 727-744.
- Uiblein, F., Durand, J. P., Juberthie, C., and Parzefall, J. (1992). ''Predation in caves: the effects of prey immobility and darkness on the foraging behaviour of two salamanders, Euproctus asper and Proteus anguis.'' Bahavioural Processes, 28, 33-40.
- Voituron, Y., de Fraipont, M., Issartel, J., Guillaume, O., and Clobert, J. (2010). ''Extreme lifespan of the human fish (Proteus anguinus): a challenge for ageing mechanisms .'' Biology Letters, Published online before print July 21, 2010, doi: 10.1098/rsbl.2010.0539 .