Scientists have discovered rod and cone cells in a well-preserved fossilized fish that is more than 300 million years old. The study reveals that these eye cells existed for over 300 million years, helping the ancient fish see in color. Our vision is based on pigments that absorb light. Notably, these pigments are found inside rods and cones, which are present in the tissue layer in the back of retina.
Fossils excavated from Kansas
Rods are sensitive to light, and are mainly responsible for night and peripheral vision. Cones are highly sensitive to color, helping perceive rapid changes and fine details. According to LiveScience, Myllokunmingia may have possessed a rudimentary camera-like eye. It indicates that the vision dates back to more than 500 million years. But, until now, little was known about color vision because soft tissues in the eye decay quickly after death.
Scientists have discovered a very well-preserved fossilized fish called Acanthodes bridgei. The specimen is at least 300 million years old. It was excavated from the Hamilton Quarry in Kansas, which was a shallow lagoon long ago. The specimen was kept at the National Museum of Nature and Science in Tokyo. Gengo Tanaka of Kumamoto University in Japan said that fossils in Kansas area are well-preserved because they were buried quickly in the lagoon’s sediments.
Resemblance between A. bridgei and modern fish eyes
The fish was about four inches long. Researchers said it was the last known common ancestor of the modern jawed fish. Rods and cones in Acanthodes bridgei were still visible under a scanning electron microscope. What’s more, they also found granules in the fish that was similar to the ones present in modern fish eyes. These granules are made up of a pigment called eumelanin, which absorbs light and helps animals see.
A. bridgei was more active during the day and relied on its vision to spot food and predators. It lived in shallow waters. Findings of the study appeared in the Dec.23 issue of the journal Nature Communications.