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A "four-eyed" fish that sees simultaneously above and below the water line has offered up a dramatic example of how gene expression allows organisms to adapt to their environment.
Gregory L. Owens, a University of British Columbia graduate student, found a sharp divide between the upper and lower sections of the eyes of Anableps anableps, a six- to 12-inch fish closely related to guppies. The findings were published today online in Biology Letters.
The four-eyed fish spends most of its life at the water surface, feeding on flying insects as well as algae, in the mangrove swamps of central America and northern South America. The upper half of its eyes penetrate the water line, while the lower half of its eyes are submerged. |
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Its opsin genes, which code for light receptors in the eye, closely resemble those of other fish species that don't see above water, so it was unknown if the four-eyed fish's eyes were adapted to both aerial and aquatic light.
Owens, while conducting research for a master's degree at the University of Victoria, sought an answer in how the opsin genes were expressed. He made several molecular probes that, when applied to the retina, would bind to specific opsin gene messenger RNA (mRNA), the molecules that translate DNA into protein synthesis. |
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