Emory University researchers have identified the first fish known to have switched from ultraviolet vision to violet vision, or the ability to see blue light. The discovery is also the first example of an animal deleting a molecule to change its visual spectrum.
Their findings on scabbardfish, linking molecular evolution to functional changes and the possible environmental factors driving them, were published Oct. 13 in the Proceedings of the National Academy of Sciences.
"This multi-dimensional approach strengthens the case for the importance of adaptive evolution," says evolutionary geneticist Shozo Yokoyama, who led the study. "Building on this framework will take studies of natural selection to the next level."
The research team included Takashi Tada, a post-doctoral fellow in biology, and Ahmet Altun, a post-doctoral fellow in biology and computational chemistry.
Vision 'like a painting'
For two decades, Yokoyama has done groundbreaking work on the adaptive evolution of vision in vertebrates. Vision serves as a good study model, since it is the simplest of the sensory systems. For example, only four genes are involved in human vision.
"It's amazing, but you can mix together this small number of genes and detect a whole color spectrum," Yokoyama says. "It's just like a painting."
The common vertebrate ancestor possessed UV vision. However, many species, including humans, have switched from UV to violet vision, or the ability to sense the blue color spectrum.
From the ocean depths
Fish provide clues for how environmental factors can lead to such vision changes, since the available light at various ocean depths is well quantified. All fish previously studied have retained UV vision, but the Emory researchers found that the scabbardfish has not. To tease out the molecular basis for this difference, they used genetic engineering, quantum chemistry and t
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