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Home » Biology Articles » Zoology » Primatology » The aye-ayes have it: The preservation of color vision in a creature of the night


A quest to gain a more complete picture of color vision evolution has led Biodesign Institute researcher Brian Verrelli to an up-close, genetic encounter with one of the world's most rare and bizarre-looking primates.

Verrelli and his ASU team have performed the first sweeping study of color vision in the aye-aye (pronounced "eye-eye"), a bushy-tailed, Madagascar native primate with a unique combination of physical features including extremely large eyes and ears, and elongated fingers for reaching hard to access insects and other foods. Verrelli, lead author George Perry, and collaborator Robert Martin's results, published in the journal Molecular Biology and Evolution, have led to some surprising conclusions on how this nocturnal primate may have retained color vision function.

Verrelli's group focuses on color vision to better understand genetic variation between human and other primate populations and the truly big evolutionary questions as to what makes us human. "At least within humans and some other primates, we know that there are three different genes responsible for color vision," said Verrelli. The genes, called opsins, come in three forms that shape our color vision palette, one for blue, another for green, and a third for red.


"These three genes may explain all the variation that we might see across human populations in color vision," said Verrelli. "But how did our range of color vision variation come to be in the first place""

To help trace back the evolution of color vision, Verrelli's 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.


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."




Arizona State University. September 2007.

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