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Brain scans shed light on the oddity of a cave salamander that lost its eyes

The cave salamander Proteus anguinus
gif: Tesařová M et al. GigaScience 2022/Gizmodo

Researchers recently scanned the heads of blind cave salamanders to find out how the species’ dark, aquatic environment shaped their senses. Using X-ray micro-computed tomography, they were able to map the internal makeup of the olm’s cranial structures, including the brain, olfactory organs, ears, facial muscles and the remains of the eyes. What they found was strange, even by salamander standards.

Proteus anguinus (called Olm or Proteus) is a slender, foot-long aquatic salamander native to southern Europe. The earliest written accounts of the animal by a 17th-century Slovenian naturalist suggest that people thought olms were the descendants of dragons. The flesh-colored salamander can live up to a century. It has an elongated head and very small arms; If you squint, the Olm looks like a super smooth snake. Its bizarre features are the result of troglomorphism – the way cave dwellers adapt to life in perpetual darkness.

A picture of the salamander and a picture of the 3D scan result.

An olm with an inset of the 3D scanned head.
photo: Gregory Aljancic

Olms are not entirely blind. The larvae are actually born with eyes that regress shortly after the animals hatch. The vestigial eyes of adult olms remain sensitive to light despite being under the skin – if you shine a light near an olm, it would likely flee. While they can’t see much, the olm’s other senses, particularly smell and hearing, are quite keen.

The team scanned the heads of the Olm and one of his relatives, the lovable axolotlat different stages of development to compare their different anatomyS. The larval and juvenile scans showed residual eyes, but the adult specimen’s residual eyes and optic nerves were probably too faint to show up in the scans. The olm’s olfactory cavities are elongated compared to those of the surface-dwelling axolotl, a sign that the blind salamander’s sense of smell improved as its eyesight declined. Other senses of the Olm, like his Electrosensitivity and its ability to detect changes in pressure in water, require further examination.

One mystery that the Olm brain scans didn’t reveal much about was the animal’s ability to regenerate. Like the axolotl, the olm is capable of regrowing body partsan ability that makes these salamanders an intriguing subject of study for the future of human medicine.

Comparison of the heads of larvae and adult olms with those of another salamander, the axolotl (Ambystoma mexicanum).

Comparison of the heads of larvae and adult olms with those of another salamander, the axolotl (Ambystoma mexicanum).
image: Tesařová M et al. GigaScience 2022/Gizmodo

The 3D models will allow scientists to “explore behavioral responses in terms of chemical cues, auditory frequencies or the emission of signals,” study author Edgardo Mauri, a researcher at Speleovivarium Erwin Pichl in Trieste, told a press release. The new paper is publish today in GigaScience. The three-dimensional models are publicto advance the study of the morphology of the olm in the future.

The genome of the axolotl was Completed for the first time in 2019, but much less is known about the Olm. The researchers hope these detailed new X-ray scans will help show how this cave salamander’s ability to regenerate may differ from its surface-dwelling relative.

More: The first two Slovenian ‘dragon babies’ have hatched

https://gizmodo.com/brain-scans-illuminate-weirdness-of-cave-salamander-tha-1848746878 Brain scans shed light on the oddity of a cave salamander that lost its eyes

Adam Bradshaw

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