动物实验,脊椎动物 z-bo 2020-11-05 347

　　The journal Nature Communications reported online the first discovery of fossil rods and cones (receptors in the visual system). The discovery of these things in a fish named Aanthodes bridgei that has been 300 million years ago shows that these visual receptors have been present in vertebrate eyes for at least 300 million years, and the vertebrates involved may be able to see colors. .

　　The evolution of vertebrate vision is an important theme in the life history of animals, but apart from the calcified lens of arthropods that have become fossils, other parts of the visual system are usually not retained in the fossil record because of the soft tissues of the eyes and brain It rots quickly within a few days after death.

　　Gengo Tanaka and colleagues studied the fossils of a fish named Aanthodes bridgei from the Upper Carboniferous Hamilton Formation in Kansas, USA. This fish is the last common ancestor of modern jawed fish and may live in very shallow brackish water. They found that the original color, shape and presence of eumelanin (a retinal pigment that absorbs light) are retained in the fish.

　　They also discovered preserved eye tissue. This discovery provided the first record of a rod and cone mineralized in a fossil. The presence of rods, cones, and melanin in the eyes of this fish indicates that retinal movement activity (today fish rely on light vision: daytime vision is provided by cones, and dusk vision is provided by more sensitive rods) in 300 million years ago It may have existed years ago. The presence of cones also indicates that this fish 300 million years ago may still have color vision, although to obtain conclusive evidence, it is necessary to obtain a photoreceptor protein called "opsin" from fossils.