Non-visual sensory physiology and magnetic orientation in the Blind Cave Salamander, Proteus anguinus (and some other cave-dwelling urodele species). Review and new results on light-sensitivity and non-visual orientation in subterranean urodeles (Amphibia)

Abstract

A review is given on several sensory systems that enable troglophile and troglobian urodele species to orient non-visually in their extreme hypogean habitat. A new sense was discovered allowing the animals to orient according to the Earth's magnetic fi eld, which could serve as a basic and always available reference for general spatial orientation. Moreover, working with permanent magnetic fi eld stimuli off ers a very sensitive experimental method to discover the urodeles' thresholds for other sensory modalities such as light, sounds, and other stimuli, perhaps in competition or combination with the magnetic one. Proteus' audition as underwater hearing and light sensitivity due to its partly remaining sensory cells and/or skin sensitivity were studied. Excellent underwater hearing abilities had been demonstrated for Proteus with an acoustic behavioural method. Th e ability of sound pressure registration in Proteus is supposed to be attained by the tight anatomical junction between the ceiling of the oral cavity and the oval window. More generally, all non-visual sensory capabilities may facilitate certain behavioral strategies, compensating for missing visual orientation. Troglobians are more likely than others to own and regularly use the sensorial †) We would like to dedicate this article to the memory of Prof. Dr. Peter Schlegel and Dr. Wolfgang Briegleb, as a review on several sensory systems that enable troglophile and troglobian urodele species to orient non-visually in their extreme hypogean habitat.Th e sudden and much too early death of Prof. Schlegel, the leading expert on the research fi eld of sensory physiology and ethology of troglophile and troglobian amphibians convulsed us.Dr. Briegleb died suddenly by accident with his delta dragon. We are grateful to him for his research opus since the late fi fties and early sixties that essentially contributed to the knowledge of Proteus ' biology, development, sensory physiology, and eco-ethology.

Marked genetic structuring and extreme dispersal limitation in the Pyrenean brook newtCalotriton asper(Amphibia: Salamandridae) revealed by genome-wide AFLP but not mtDNA

“…2008). A limited survey by Schlegel et al. (2009) found two nucleotide changes in the control region sequence of six individuals from three French localities, but the limited sampling precludes any further inference.…”

Environmental DNA in subterranean biology: range extension and taxonomic implications for Proteus

“…Significantly, despite a low degree of sequence divergence between the two populations observed in the mitochondrial control region141545, none of the comparative studies to date have detected any signs of their interbreeding, e.g. haplotype sharing1415 or intermediate morphology101213464748. In combination with these observations, eDNA data suggest that the two populations may represent independent species, but additional analyses are needed to resolve the taxonomic status of the present as well as of other apparently monophyletic groups of Proteus .…”

History and biology of the «black proteus« (Proteus anguinus parkelj Sket & Arntzen 1994; Amphibia: Proteidae): a review / Zgodovina in biologija črnega močerila (Proteus anguinus parkelj Sket & Arntzen 1994; Amphibia: Proteidae): pregledni članek

“…The mouth cavity (which is frequently filled with air that is not used in breathing activity) and lungs, together with the inner ear, act as underwater sound pressure transducers (Bulog 1990). The ability of sound pressure detection in Proteus is probably enhanced with the tight anatomical junction between the ceiling of the gas filled oral cavity and the oval window of inner ear (Bulog 1998;Bulog & Schlegel 2000;Schlegel et al 2009). A three-dimensional model of the inner ear made from serial semithin sections of the otic region in both subspecies of Proteus enabled a comparative analysis and reconstruction of sensory epithelia and the perilymphatic system (Konec 2009;Konec & Bulog 2010) (Fig.…”

“…The sound detection ability in both subspecies of Proteus is in the frequency range from 10 to 15000 Hz with the greatest sensitivity reached at 1500 Hz for P. a. anguinus and 2000 Hz for P. a. parkelj (Bulog & Schlegel 2000;Schlegel et al 2009). This range of audible frequencies provides the unique ability to detect sound waves underwater and surpasses all amphibians and most fish that have been studied.…”

“…Behavioral studies suggest that Proteus (both subspecies) is also able to detect and orient itself to magnetic fields (Aljančič & Bulog 1999;Schlegel et al 2009). For these studies the animals were in round containers surrounded by large coils for manipulating the magnetic field.…”