How Snakes Actually Inject Venom

[Melllvar]

Apparently only 1/7th of them have hollow fangs. Anyway, I found the article about it (Biophysics of Snakebites on sciencedaily.com) quite interesting. Not just about the snakes and their fangs, but the properties of snake venom and non-Newtonian fluids. Do give it a read.

Full text:

Most snakes do not inject venom into their victims bodies using hollow fangs, contrary to common misconceptions. The fact is that most snakes and many other venomous reptiles have no hollow fangs. Physicists have now uncovered the tricks these animals use to force their venom under the skin of their victims.

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 fangs. Yet, even though the vast majority of venomous reptiles lack hollow fangs, they are effective predators.

Only around one seventh of all venomous snakes, like the rattlesnake, rely on the trick with the hollow 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 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.

The researchers also found an answer to the question of how snakes manage to ferry the venom well under the skin of their prey. After all, only there can it unfold its deadly effect. Here too, snakes developed a trick in the course of evolution: When a snake attacks, the fang grooves and the surrounding tissue form a canal. Just like blotting paper, the tissue sucks the venom through this canal. And snake venom has a very special property to facilitate this effect: Just like ketchup, which becomes significantly more fluid upon shaking, the sheer forces that arise from the suction cause the venom to become less viscous, allowing it to flow through the canal quickly as a result of the surface tension.

Scientists refer to substances with these characteristics as non-Newtonian fluids. These have a very practical consequence for snakes: As long as there is no prey in sight, the venom in the groove remains viscous and sticky. When the snake strikes, the venomous "tears" flow along the groove -- just like wine along a glass -- and into the wound, where the venom takes its lethal effect.

 

[Tangent]

Nice. That was interesting. And thoroughly comprehensive. Did you know that there are quite a few venomous lizards? And I dont just mean those that harbor masses of bacteria in their mouth. Creepy.

 

[Melllvar]

Wow, I had totally forgotten making this thread.

Did you know that there are quite a few venomous lizards? And I dont just mean those that harbor masses of bacteria in their mouth. Creepy.

Actually, you know Komodo Dragons, those giant lizards that aren't venomous but have such nasty bacteria in their mouth it pretty much acts as a venom anyway? Turns out that was a bunch of BS and they really are venomous (in addition to the oral bacteria and septic effects that were already known). Recent discovery. Although it seems the bacteria is still the primary mode of damage from a bite.

In late 2005, researchers at the University of Melbourne speculated that the perentie (Varanus giganteus), other species of monitor, and agamids may be somewhat venomous. The team believes that the immediate effects of bites from these lizards were caused by mild envenomation. Bites on human digits by a lace monitor (V. varius), a Komodo dragon, and a spotted tree monitor (V. scalaris) all produced similar effects: rapid swelling, localized disruption of blood clotting, and shooting pain up to the elbow, with some symptoms lasting for several hours.[31]

In 2009, the same researchers published further evidence demonstrating that Komodo dragons possess a venomous bite. MRI scans of a preserved skull showed the presence of two venom glands in the lower jaw. They extracted one of these glands from the head of a terminally ill specimen in the Singapore Zoological Gardens, and found that it secreted a venom containing several different toxic proteins. The known functions of these proteins include inhibition of blood clotting, lowering of blood pressure, muscle paralysis, and the induction of hypothermia, leading to shock and loss of consciousness in envenomated prey.[32][33] As a result of the discovery, the previous theory that bacteria were responsible for the deaths of komodo victims was disputed.[34]

Kurt Schwenk, an evolutionary biologist at the University of Connecticut finds the discovery of these glands intriguing, but considers most of the evidence for venom in the study to be "meaningless, irrelevant, incorrect or falsely misleading". Even if the lizards have venomlike proteins in their mouths, Schwenk argues, they may be using them for a different function, and he doubts that venom is necessary to explain the effect of a Komodo dragon bite, arguing that shock and blood loss are the primary factors.[35][36]

This of course has nothing to do with anything, but I'm posting it anyway.

 

[Tangent]

Indeed, I had heard that before! I went to the zoo not so long ago and stared at the creepy komodo thinking just that.