Where is the bat’s sixth sense?

A team led by Dr. Oliver Lindecke and PD Dr. Christian Voigt from Leibniz-IZW for the first time demonstrated that the environmental signals important for navigation over long distances are received through the cornea of eye. They performed these experiments with bats and found that the bat’s sense of direction lies in … the eye.

The bat’s sense of direction are the eyes. Mammals see with the eyes, hear with the ears, and smell with the nose. But which senses or organs allow them to direct their migration, sometimes beyond their feeding area and thus require extensive orientation? Scientific experiments led by the Leibniz Institute for Animal and Wildlife Research (Leibniz-IZW) led by Professor Richard A. Holland (Bangor University, UK) and Dr. Gunārs P ē tersons (Latvian University of Life Sciences and Technology). It shows that the cornea of ​​the eye is now an important sensory site for bat migration. If the cornea is anesthetized, another sense of reliable direction is disturbed while its ability to detect light remains unaffected. The article was published in the scientific journal Communications Biology. In the bats of an experimental group, the scientists localized the cornea with a drop of oxybuprocaine. This surface anesthetic is widely used in ophthalmology, where it is used to temporarily desensitize the cornea when the human or animal eye is overly irritated. However, the influence on the orientation has not been noted before. In another group of experimental bats, the team anesthetized the cornea of ​​one eye. Individuals in the control group received no anesthesia, but instead received an isotonic saline solution as eye drops. All animals in this scientific experiment were caught in a migration corridor on the Baltic coast and released individually in open fields 11 km from the capture site. First, scientists used bat detectors to ensure that there were no other bats in the field at the time of releasing the test animals. One observes the movement of the released bats not knowing how the bats have been treated experimentally. Dr. Oliver Lindecke, the first author of the paper, explains: “The control group and the one-sided corneal anesthetic group had a clear orientation to the expected south, while the bats with the cornea were anesthetized. the two sides fly in random directions. ” “This obvious difference in behavior suggests that corneal anesthesia disrupted the sense of direction, but the ability to orient seems to still work well with one eye,” he added. After a short time the corneal treatment ended, the bats were able to resume their journey south after the test. ” To rule out the possibility that an irritated cornea also affects visual sensations and so scientists could have come to the wrong conclusion, they performed an additional test. Again, they tested to see if a bat’s response to light changed after anesthesia on one or both sides. “We know from previous research that bats prefer a illuminated exit when leaving a simple Y-shaped maze,” explained PD Dr. Christian Voigt, head of the Leibniz-IZW Department of Evolutionary Ecology. . “In our experiment, animals under one or two side anesthesia also showed this preference,” he said; we can therefore rule out that light vision has been altered after corneal treatment. Light visibility will of course affect long-distance navigation as well. ” For example, many vertebrate species such as bats, dolphins, whales, fish and turtles can navigate safely in the dark, whether it is under the open night sky, when it is cloudy at night. or in caves and tunnels as well as in the depths of the ocean. For decades, scientists have been searching for the senses or a sensory organ that makes it possible for animals to perform navigation and navigation tasks that seem unimaginable to humans. The magnetic sensation has so far been demonstrated only in some mammals. Experiments have shown that iron oxide particles in a cell can act as “microscopic compass needles”, as is the case with some species of bacteria. The team’s experiments on Lindecke and Voigt provide, for the first time, reliable data for the determination of sensory orientation in free-migrating, migratory mammals. Exactly what a bat’s cornea looks, how it works, and whether it is a long-sought magnetic sense needs to be pointed out in future scientific investigations.