To help trace back the evolution of color vision, Verrellis collaborator Perry turned to the endangered aye-aye, a primate representative of lemurs. These primates split from other groups including humans, apes, and monkeys more than sixty million years ago, and are thought to be in some ways representative of the early primates that lived at that time. We chose the aye-aye specifically because it has a very interesting behavior in that it is fully nocturnal, and so, it raises an obvious and straightforward question: If you are an animal that lives at night, do you need color vision"
In a simple case of use it or lose it, the prevailing theory suggested that nocturnal primates cannot use color vision to see, and so the genes that they have for color vision accumulated mutations and degraded over evolutionary time.
From a practical standpoint, studying color vision in the aye-aye proved to be a daunting endeavor. Since the aye-aye is an endangered species, obtaining DNA samples in the wild was not possible. The group turned to a few rare international research institutions and colleagues that have aye-ayes to obtain DNA samples for their study.
In all total, they obtained samples from eight aye-ayes for their study. It took a year and a half to analyze the samples, since Perry and Verrelli had to invent the methodology to perform the first wide-range genetic analysis on the aye-aye. From a conservation, population and functional viewpoint, it was the first study of its kind, said Verrelli.
The results his team found were so startling that they had to recheck them twice. When examining these genes in the aye-aye, we realized that they are not degrading, said Verrelli. In fact, for the green opsin gene, we did not find a single mutation in it. The opsin genes look to be absolutely fully functional, which is completely counter to how we had believed color vision evolved in nocturnal mammals.
|Contact: Joe Caspermeyer|
Arizona State University