Researchers at Kyoto University have shown that by altering the properties of photosensors (photoreceptive proteins), frogs are adapted to have the ability to discriminate colors in the dark.
In many vertebrates, there are three types of photoreceptor cells (cones) that work in bright places, and because they have photoreceptor proteins that absorb red, green, and blue light, they can distinguish colors.On the other hand, there is only one type of photoreceptor cell (rod) that works in a dark place, and it is not possible to distinguish colors.
Frogs are exceptionally known to discriminate colors even in the dark.In addition to the normal rods of many vertebrates (including rhodopsin, a photoreceptive protein that absorbs green well), frogs also have green rods that contain blue-sensitive pyramidal visual pigments. It has been thought that rods can be used to distinguish colors in the dark.
This time, a group at Kyoto University investigated the properties of rhodopsin and blue-sensitive pyramidal visual pigments, which are present in each of the two rods.Rhodopsin was originally known to have a low noise response and properties suitable for "vision in the dark", but even in the blue-sensitive pyramidal visual pigment that should be responsible for "vision in the light", frogs In this case, it was clarified that by changing one amino acid residue, the property was changed to be suitable for "vision in the dark".
By having multiple rods that work in the dark like this, the frog has acquired the special ability of "color vision in the dark".This is an advantageous feature for nocturnal frogs.
Paper information: [Proceedings of the National Academy of Sciences of USA] Adaptation of cone pigments found in green rods for scotopic vision through a single amino acid mutation
