BEIJING, Oct. 29 (Xinhuanet) -- The first prehistoric
fish that made its way onto land looked around and saw a full range of colors,
including wavelengths of light that human eyes cannot see, a new study
suggests.
Scientists have discovered the retinas of Australian
lungfish (Neoceratodus forsteri) contain visual pigment genes that are more
similar to those of tetrapods ¡ª four-legged land animals with backbones ¡ª than
those of other fish. They also found evidence the fish can see in
ultraviolet.
Helena Bailes of the University of Queensland in
Australia and her colleagues analyzed the Australian lungfish DNA that codes for
opsin, a visual pigment found in cone cells required for seeing in color.
Comparing it to other creatures, they found that it more closely resembled the
opsin of amphibians and reptiles than other fish.
"The visual system of N. forsteri may represent an
evolutionary design most closely reflecting that present just prior to the
emergence of land vertebrates in the Devonian Period," Bailes said.
Australian lungfish are thought to be the closest
surviving relatives of the first land animals. The "living fossils" have
remained virtually unchanged since first appearing in the fossil record 135
million years ago. They still live in Australian rivers.
The team also spotted four types of cone cells in the
lungfish eyes, suggesting the fish can see in colors we humans can't. "From
looking at the DNA sequence, they certainly have the potential to see in the
[ultraviolet] range and further into the red range than humans," Bailes said.
Cones are light receptors in the eye that are
sensitive to color, while "rods" are better at seeing in dim light. Humans have
three types of cone cells in their eyes: red, green, and blue. "That's why TVs
are made of red, green and blue pixels," Bailes told LiveScience.
(Agencies)
