New discovery of bat's observation ability

The eyes of night bats have two types of cones to observe daylight and distinguish colors. Scientists at the Max Planck Brain Research Institute, Frankfurt and Oldenburg University discovered cone cells and visual pigments in two pollen-eating bats. With the retinal electrophoresis technique, they found that the ability to sense ultraviolet rays increased in light-stimulating light conditions.

The researchers concluded that bat eyes have an adaptive structure for both daylight and ultraviolet light. UV-sensitive eye hats bring many benefits to bats, including enhancing visual orientation when dusk, avoiding predators, and detecting UV-reflecting flowers (for chocolate). feeding bat species on nectar).

Bats are mammals of the bat (Chiroptera). This set is divided into two subdivisions: big bat (Megachiroptera) and small bat (Microchiroptera). Small bats (photos 1 and 2) have smaller eyes and visual centers in the brain than larger bats. In bats, sight plays an important role in detecting prey and avoiding enemies when feeding or resting.In addition, bats are always exposed to ambient light at varying levels throughout the day, depending on their sleeping conditions.

Eye retina in mammals with rod light sensing cells to receive night light, and cone light receptor cells to receive daylight and observe colors.

Small bat eyes are small and the retina contains rod cells. This motivates Brigitte Müller and colleagues at Max Planck Brain Research Institute in Frankfurt / Main to study the light-stimulating cells in bats eating pollen by tissue biological analysis and molecule, with help from Josef Ammermüller's team in retinal electroencephalography.

To identify different types of light-stimulating cells, the team stained the retina of two small bat species with opsin antibodies. As expected, both species have very thick rod cell density, typical for night vision.In addition, they also have cones with a ratio of 2 to 4%.

'The rate of such cones is quite small, but by studying other nocturnal mammals such as mice, we know that this ratio allows to see in daylight,' Brigitte Müller, the leader of the research team, said. For two species of bats that eat pollen, Glossophaga soricina and Carollia perspicillata (live mainly in Central and South America), the marked opsin has shown two types of specific spectral cone cells of mammals and cones. form L and cones in the form S (Figure 3).

Falling Carollia perspicillata is flying. Researchers have concluded that bat eyes are suitable for both daylight and ultraviolet light conditions. (Photo by Cornelia Hagemann, University of Goethe, Frankfurt / M, Germany)

A few years ago, when studying bats eating Glossophaga soricina in dark conditions, scientists found no evidence of color discrimination, but discovered the ability to perceive ultraviolet rays. Violet. They concluded that it was a product of rod-shaped opsin, and that G. soricina bat lacks separate short-wavelength sensory cones.Recent molecular studies have found cone opsin genes in different bat species but there is no evidence of their existence in retinal cells.

Considering all of these results, Müller and his colleagues came to the conclusion that the retina's ability to perceive ultraviolet light in both species comes from the ratio of rod cells to opsin S. Measurements of transmissions of corneal and vitreous species in G. soricina and C. perspicillata show that ultraviolet light (with a wavelength of about 350 nanometers) actually reaches the retina in bat eyes.

'Our research results show the ability to sense ultraviolet light produced by cones in phyllostomid bats (leaf bat),' says Brigitte Müller. 'Moreover, with two types of cone cells, bats have the condition to distinguish two color phases - this is a common characteristic in many mammals. The use of cones along with rod-shaped cells in the observation helps to improve this species 'ability to receive visual information.'

For bats, sight is important in both feeding and resting, as well as in avoiding enemies. The ability to observe in low light conditions (when simultaneously stimulating light levels of rods and cones) is often promoted at dawn, dusk or in the moonlit night. For both bat species in this study, the ability to perceive ultraviolet light increases the level of success in feeding, because many flowers are the food of the bat reflecting ultraviolet rays.

Refer
Müller B, Glösmann M, Peichl L, Knop GC, Hagemann C, et al.Bat Eyes Have Ultraviolet-Sensitive Cone Photoreceptors.PLoS ONE, 4 (7): e6390.DOI: 10.1371 / journal.pone.0006390