First land animals would have wanted a color TV 2007-10-29 15:42:50   Print

    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 four-legged land animals with backbones 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.


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Editor: Gareth Dodd
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