IN a press release from Emory University, located in Atlanta, we read: Fish Vision Discovery Makes Waves in Natural Selection. Here are some excerpts, with bold added by us:
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.
That link is to the full text, which requires a subscription; but you can see the abstract here: Evolutionary replacement of UV vision by violet vision in fish. While we’re providing links, here’s some information on the scabbardfish. Fitch’s scabbardfish, the subject of the Emory research, is listed under Genus Lepidopus. Here’s more on the specific species: Lepidopus fitchi.
“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 next level? Here’s more:
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.”
Got that? They can look at a few genes and then know what part of the spectrum a creature could see. Moving along:
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.
So if you can see the blue sky, perhaps you’re descended from a scabbardfish — Lepidopus fitchi to be precise. We can already hear the creationists protesting: “I ain’t no kin to no scabbardfish!”
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.
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, Yokoyama theorizes.
Okay, so where is all this taking us? One last excerpt:
“Evolutionary biology is filled with arguments that are misleading, at best,” Yokoyama says. “To make a strong case for the mechanisms of natural selection, you have to connect changes in specific molecules with changes in phenotypes, and then you have to connect these changes to the living environment.”
Very nice, but we sense an opportunity for the quote-miners here. Yokoyama may wish he had been more circumspect in his phraseology.
This is presumptuous of us, because it’s entirely up to the researchers to describe their work, but solely for the purpose of thwarting an almost inevitable creationist misinterpretation, we would have put it like this:
[Curmudgeon’s version:] Now that research like this is possible, we have the ability to test specific predictions of evolutionary biology and to provide empirical support for theory at a level of detail not previously attainable.
But the researchers are more interested in describing their work than they are in blunting the objections of creationists. That is as it should be.
Copyright © 2009. The Sensuous Curmudgeon. All rights reserved.