The African clawed frog is tongue-less, has long, curvy toes and eyes that are perched on top of its head, but that’s not all that’s odd about it. This species of frog also took a strange evolutionary path to change from ultraviolet to violet vision: Some of its visual pigment molecules kept trying to leap ahead, but other molecules shut them down and kept the process moving at a crawl.
Science Advances published the complete molecular interactions involved in the pathway, as detailed in a study led by Shozo Yokoyama, a biologist at Emory University who specializes in adaptive evolution of vision.
“It’s the most bizarre, and sophisticated, case of color vision evolution that I’ve ever encountered,” says Yokoyama, who previously headed up efforts to construct the most extensive evolutionary tree for vision, including 500 species of animals, from eels to humans.
“This frog had these quirks for rapid molecular change, but it also had something to control these quirks,” he says. “In fact, it had triple protection.”
The story of the evolution of color vision in the African clawed frog "is full of mysterious twists and turns," says evolutionary biologist Shozo Yokoyama.