Poisonous fangs in snakes were not formed to supply poison

Poisonous fangs in snakes were not formed to supply poison
Poisonous fangs in snakes were not formed to supply poison
Anonim

Ever wondered how deadly snakes got fangs? The answer lies in the microscopic features of their teeth. This was shown by a study by a team of scientists from several Australian and Canadian universities. An article describing the origin of poisonous snake fangs was published in the scientific journal Proceedings of the Royal Society B.

"It has always been a mystery why canines are so common in snakes, but rarely in other reptiles. Our study provides an answer to this question by showing how easily normal snake teeth turn into hypodermic needles," says lead author Alessandro Palci. Alessandro Palci of Flinders University, Australia.

Of the nearly 4,000 snake species living today, about 600 are considered venomous. When bitten, they inject venom through a groove in their canine teeth. The venom is fed into a pressurized groove from a gland next to the canine.

Fang from the upper jaw of a gabun viper

Taipan's skull and its left canine in section to demonstrate the relationship between the venom groove and folds at the base of the tooth

Poisonous fangs are modified teeth with grooves. They are larger than the rest of the teeth and can be located on the jaw of the snake, both behind and in front of it.

An international team of researchers has performed computer scans of the teeth of fossil snakes and current reptiles. The result of computed tomography led scientists to the hypothesis that grooves in the teeth of prehistoric snakes appeared at first not for injecting poison, but for firmly attaching huge canines in the jaw. Scientists have made sure that ancient snakes initially lacked venom delivery systems (that is, canines and associated venom glands), which are found only in their distant descendants.

To test their hypothesis, scientists used mathematical modeling of the evolutionary process of snake fangs.

Simulation results showed that grooves formed in tiny plicidentine folds at the base of large serpentine teeth.

Plicidentin is a folded dentin found in prehistoric cross-finned fish, labyrinthodonts, ichthyosaurs, and monitor lizards. This material is intermediate between bone and dentin. Recall that dentin is the hard tissue of teeth covered with enamel. Plicidentin is responsible for the attachment of teeth to the jaws in amphibians and reptiles (except crocodiles).

Prior to this study, it was believed that plicidentin is almost completely absent in modern reptiles, with the exception of some monitor lizards, the authors of the scientific work write.

According to the scientists in their article, the results provide the first conclusive evidence that plicidentin is indeed widespread among snakes (both venomous and non-venomous) and is the basis for the formation of venom grooves in modern snakes.

So, the folds of plicidentin, like anchors, first helped the snake's fangs to attach more firmly to the jaw. Then, during a random mutation, one of the folds of plicidentine turned into a groove that extended to the tip of the tooth and opened a hole in it. Another mutation, which happens all the time in the course of evolution, pushed the poisonous gland to the tooth with a groove, and the poison accidentally began to fall into the groove.

Snakes with the resulting poisonous fang gained an advantage over their relatives, receiving more food as a result of hunting. Evolutionary selection liked this advantage, as a result of which it was consolidated and later developed further. As a result, the world today has about 600 species of poisonous snakes.

“Our work also emphasizes opportunism and the effectiveness of evolution.The folds that helped attach the teeth to the jaw were altered [by evolution] to help inject poison, "explains co-author Michael Lee of Flinders University.

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