By examining the genetics of snake embryos, researchers have solved a long-standing evolutionary mystery regarding the evolution of fangs on venomous snakes. Researchers have been puzzled because the fangs, which are syringe-like teeth that draw poison from venom glands, have very different placement in different species. Most venomous snakes, including grass snakes, have fangs positioned in the rear of the mouth, while a few groups, including rattlesnakes, cobras and vipers, have fangs jutting down from their upper jaws in the front of the mouth [LiveScience].
Adding to the confusion, researchers had found that the front-fanged snakes aren’t closely related to each other, suggesting that the front-fang trait evolved at least two separate times. The assumption of multiple origins is problematic for evolutionary biologists who prefer to find that complex structures like fangs … don’t just come and go. If they did, fangs presumably would have popped up in other vertebrates [Science News].
In the new study, which was published in the journal Nature [subscription required], researchers examined the expression of tooth-forming genes in over 90 snake embryos, and found that fang development looks the same in the embryos of all venomous snakes; all fangs originate in the back of the mouth, but at a certain stage of development, the fangs of the some snakes migrate to the front of the mouth. “When you get a finding like that, where the fangs in all kinds of adults come from the same place in the embryo … it supports the idea that there’s an evolutionarily common origin for the fang and that it hasn’t evolved totally independently,” explains [study coauthor] Michael K. Richardson [Science News].
Researchers say snakes first evolved to have venom glands, and then improved the system by gaining the fangs that could swiftly deliver venom through animals’ thick hides. They say this evolutionary event could have contributed to the massive increase in snake diversity and numbers in the Cenozoic era, which started about 65 million years ago. “Snakes are a relatively young group,” says [herpetologist Rick] Shine. “But they are one of the great success stories in recent times in an evolutionary sense” [ABC Science].
Image: F. Vonk and M. Richardson