Scientists identify first fish that switched from ultraviolet vision to violet vision

Washington, October 17 (ANI): Researchers from Emory University, US, have identified the first fish known to have switched from ultraviolet vision to violet vision, or the ability to see blue light.

Their findings on scabbardfish links molecular evolution to functional changes and the possible environmental factors driving them.

"This multi-dimensional approach strengthens the case for the importance of adaptive evolution," said evolutionary geneticist Shozo Yokoyama, who led the study. Building on this framework will take studies of natural selection to the next level," he added.

The research team included Takashi Tada, a post-doctoral fellow in biology, and Ahmet Altun, a post-doctoral fellow in biology and computational chemistry.

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.

"It's amazing, but you can mix together this small number of genes and detect a whole color spectrum," Yokoyama said. "It's just like a painting," he added.

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.

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 theoretical computation to compare vision proteins and pigments from scabbardfish and another species, lampfish.

The results indicated that scabbardfish shifted from UV to violet vision by deleting the molecule at site 86 in the chain of amino acids in the opsin protein.

"Normally, amino acid changes cause small structure changes, but in this case, a critical amino acid was deleted," Yokoyama said.

According to Yokoyama, Scabbardfish spend much of their life at depths of 25 to 100 meters, where UV light is less intense than violet light, which could explain why they made the vision shift.

"Comparing violet and UV pigments in fish living in different habitats will open an unprecedented opportunity to clarify the molecular basis of phenotypic adaptations, along with the genetics of UV and violet vision," he said. (ANI)