How fangs developed in venomous snakes

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Washington, July 31 : New researcher from Leiden University in the Netherlands suggests that both rear and front fangs in venomous snakes developed from separate teeth-forming tissue at the rear of the mouth, unlike non-venomous snake dentition and human teeth.

Experts associate with this work say that it may help explain why snakes flourished beginning some 60 million years ago, geologically soon after non-avian dinosaurs went extinct. "The snake venom system is one of the most advanced bioweapon systems in the natural world. There is not a comparable structure as advanced, as sophisticated, as for example a rattlesnake fang and venom gland," Live Science quoted lead researcher Freek Vonk as telling Nature magazine.

Only the venomous snakes sport fangs - sharp, enlarged teeth positioned along the upper jaw at the front or rear of a snake's mouth, and connected to venom glands.

The non-venomous snakes like pythons are equipped with only the normal rows of teeth.

The researchers say that even a venomous snake may sometimes impart a "dry" bite, not delivering the potent venom.

While most venomous snakes have fangs positioned in the rear of the mouth, some like rattlesnakes, cobras and vipers, have fangs jutting down from their upper jaws in the front of the mouth.

"If you want to eat a very dangerous prey, like a big rat with razor-sharp rat teeth, then it would be more advantageous to have your fangs in front of the mouth so you can just bite it quickly and then let go, instead of biting it and holding on and then chewing the venom into the tissue, because then the rat can bite back," Vonk said.

With a view to determining how both types of snake fangs evolved from non-fanged species, the researchers looked at fang development in 96 embryos from eight living snake species.

Vonk says that the analyses conducted by him and his colleagues showed that the front and rear fangs develop from a separate teeth-forming tissue at the back of the upper jaw.

For all front-fanged venomous snake species, the front fangs displaced forward during embryo development by rapid growth of the embryonic upper jaws.

The rear fangs stayed put where they formed, said the researchers.

"The uncoupled rear part of the teeth-forming tissue evolved in close association with the venom gland, thereafter forming the fang-gland complex. The uncoupling allowed this to happen, because the rear part of the teeth-forming tissue did not have constraints anymore from the front part," Vonk said.

He said that the separate development of the rear part of the tissue might have played a major role in snakes' ability to diverge into the 3,000 species found throughout the world at present.

"It sheds light on one of those nagging questions in herpetology - how did a diversity of fang types among snakes evolve?" said David Kizirian, a herpetologist at the American Museum of Natural History in New York who was not involved in the study.

ANI

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