This mysterious frog has gained full teeth over the course of evolution – National Geographic

This mysterious frog has gained full teeth over the course of evolution - National Geographic

But the return of teeth in a tree-tooth frog is perhaps one of the most likely examples. In 2011, evolutionary biologist John Wiens reconstructed the evolutionary relationships among 170 different species of frog, to create a timeline from when the frogs lost their bottom teeth 230 million years ago, and when the toothed tree frog regained them. He found that the animals only regained their lower teeth about 20 million years ago, an “unparalleled length” between the loss of a trait and its return.

Wiens, who is currently at the University of Arizona and was not involved in the latest research, believes that G. Guentheri He had an advantage in developing teeth again: the animal still had a functional tooth-making genetic network in its lower teeth.

“They didn’t have to develop those teeth from scratch,” Wiens says. “It was just a matter of moving them to a place where they hadn’t been for 200 million years.”

This may not have been possible with other amphibians capable of jumping, such as frogs, which have no teeth at all. University of Michigan-Dearborn biologist John Abramian, who was also not involved in the study, studied the genes involved in enamel production in frogs, which lost all their teeth about 60 million years ago. He found that genes had morphed into “pseudogenes” over millions of years.

“These are basically genes that no longer do a job,” Abramian explains, and they are ineffective. “But since most frogs still make teeth in their upper jaw, they have all the resources to make working teeth. That makes it a smaller leap from an evolutionary standpoint.”

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Evolutionary puzzle

This doesn’t say anything about why or how the species regained its lower teeth, Balu said, although its diet certainly played a role. Teeth are the primary tools animals use to nibble and chew their food, so their appearance often depends on what’s on the menu. According to Paluh, the frogs’ fondness for small insects and the sticky tongue they use to catch their prey is why teeth are becoming less important for some species. but G. Guentheri Likes larger prey, such as lizards and other frogs. With such larger victims, it is probably helpful to have lower teeth to prevent them from wriggling out of a predator’s mouth.

But if that’s why the tree-tooth frog developed its teeth again, why didn’t the carnivorous frogs do the same? Some frogs, such as the stocky Surinamese horned frog, have serrated teeth in their lower jaw that help them grab onto their prey. But these are bony growths that do not contain dentin or enamel.

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Answers can be found in the embryos of tree-tooth frogs, says Alexa Sader, an evolutionary biologist at the University of California-Los Angeles. Her research focuses primarily on the evolution of bat teeth, but she recently described several cases of trait loss that were still present in the early stages of the animal’s development. She believes that comparing embryos of tree-tooth frogs with those of other frog species could provide more knowledge about how and when genes turn tooth formation on or off.

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She believes that as more research is done on embryos, there will be more evidence of teeth disappearing during the animal’s development, and more knowledge about the genetic wiring involved.

Balloh also hopes to be able to conduct genetic research into frog evolution, but the chance of doing so with live embryos is slim: there have been no live samples from them since 1996. G. Guentheri More so, not even in the wet volcanic hills of Parque nacional Cotacachi-Cayapas in Ecuador, where the animals once lived in great numbers. Little is known about this species, but the population has shrunk due to advances in agriculture and forestry in the cloud forests of Ecuador and Colombia. There are fears that this species has already become extinct.

But it also happens that a species of frog that was supposed to become extinct is seen again. For example, in 2018, researchers found the horned marsupial frog (Gastrotheca cornuta) after being unnoticed for thirteen years. The discovery was made in the same cloud forests in Ecuador where the tree-toothed frog was found.

Baloo hopes that one day this animal will be found again. Only because it is necessary to know the teeth of these amphibians and to solve this evolutionary puzzle, seeing living specimens of this species.

This article was originally published in English at nationalgeographic.com

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