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For years Professor Leo von Hemmen, a biophysicist at the TU Muenchen, and Professor Bruce Young, a biologist at the University of Massachusetts Lowell, have been researching the sense of hearing in snakes. While discussing the toxicity of their snakes, it dawned on them that only few snakes inject their venom into their victims' bodies using hollow poison fangs. Yet, even though the vast majority of poisonous reptiles lack hollow fangs, they are effective predators.
Only around one seventh of all poisonous snakes, like the rattlesnake, rely on the trick with the hollow poison fang. The vast majority has developed another system. A typical representative of this class is the mangrove pit viper, Boiga dendrophila. Using its twin fangs, it punches holes into the skin of its victims. The venom flows into the wound between the teeth and the tissue. But there is an even easier way: many poison fangs simply have a groove the venom flows along to enter the wound.
The researchers asked themselves how this simple method could be so successful from an evolutionary perspective, considering that bird feathers, for example, should be able to easily brush away any venom flowing along an open groove. To get to the bottom of this mystery, they investigated the surface tension and viscosity of various snake venoms. The measurements showed that snake venom is amazingly viscous.
The surface tension is high, about the same as that of water. As a result, the surface energy pulls the drops into the fang grooves, where they then spread out. In the course of evolution, snakes have adapted to their respective preferred prey using a combination of optimal fang groove geometry and venom viscosity. Snakes that prey on birds developed deeper grooves to keep the viscous venom from being brushed away by bird feathers.
|Contact: Dr. Andreas Battenberg|
Technische Universitaet Muenchen