Mammals usually look with their eyes, hear with their ears, and smell with their noses. But what kind of sensation or organ allows them to determine their direction as they migrate? Their migration sometimes extends far beyond the local foraging area and requires expanded navigational capabilities. Scientific experiments led by leibniz-IZW, a scientific experiment with Professor Richard A. Holland (Bangor University, UK) and Dr. Gunnars Pētersons (Latvia University of Life Sciences and Technology), now show that the cornea of the eye is a source of important sensations for bats.
If the cornea is anesthetized, the otherwise reliable sense of direction is disturbed, while the perception of light is not affected. The experiment showed the location of magnetic sensations in mammals. The paper was published in the scientific journal Communication Biology.
The team, led by Dr. Oliver Lindecke and Dr. Christian Voigt of Leibniz-IZW, has for the first time demonstrated that environmental signals important for long-distance navigation are received through the corneas of the eye. They experimented with Pipistrellus nathusii during the late summer migration.
In a test group of bats, scientists used a drop of Obkain to perform a local anesthetic on the cornea. This surface anesthetic is widely used in ophthalmology and is used to temporarily desensitize a patient’s cornea when the eyes of a person or animal are overstimulated. However, the effect on directional forces has not previously been recorded. In another test group of bats, the team anesthetized only the corneas of one eye. The individuals in the control group were not anesthetized but received ISO-salt water as eye drops. All the animals in this scientific experiment were captured in the migration corridor of the Baltic coastline and released separately in inland open spaces 11 km from the capture site immediately after treatment.
The Nathusius bat was captured during the experiment (Pipistrellus nathusii). Source: Oliver Lindecke Photo
The scientists first used bat detectors to make sure there were no other bats above the site at the time of release, and the experimental animals may follow them. People who observe the direction of movement of released bats don’t know how bats are treated experimentally. “The control group and the one-sided cornea anesthesia group headed southwards as expected, while the bats with bi-sided corneal anesthesia flew in a random direction,” explained lead author Dr. Oliver Lindek.
“This apparent behavioral difference suggests that corneal anesthesia destroys the sense of direction, which works well with one eye.” Because the cornea’s anesthetic effect disappears in a short time, the bats can resume their southbound course after the experiment. “For the first time here, we have observed in experiments how a migratory mammal is being taken off course — a milestone in behavior and sensory biology that allows us to study pilot systems in a more targeted way.”
To rule out the possibility that anesthesia on the cornea can also affect vision, leading scientists to draw false conclusions, they conducted a complimentary test. Again divided into experimental and control groups, they tested whether the bat’s response to light changed after one or both cornea anesthesias.
Dr. Christian Voigt, head of the Department of Evolutionary Ecology at Leibniz-IZW, explained: “We know from previous studies that bats prefer to light exits when they leave a simple Y-shaped maze. In our experiments, animals with one- or two-sided anesthesia also showed this preference; Of course, the ability to perceive light also affects long-distance navigation.”
