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Kil
Evil Skeptic
USA
13476 Posts |
 Posted - 05/19/2009 : 12:00:55
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Here's one for filthy.
Venomous Komodo dragons kill prey with wound-and-poison tactics
For the longest time, people believed that the world's largest lizard, the Komodo dragon, killed its prey with a dirty mouth. Strands of rotting flesh trapped in its teeth harbour thriving colonies of bacteria and when the dragon bites an animal, these microbes flood into the wound and eventually cause blood poisoning.
But that theory was contested in 2005 when Bryan Fry from the University of Melbourne discovered that a close relative, the lace monitor, has venom glands in its mouth. The discovery made Fry suspect that Komodo dragons also poison their prey and he has just confirmed that in a whirlwind of a paper, which details the dragon's "sophisticated combined-arsenal killing apparatus". |
Snip:
The venom itself consists of over 600 toxins, a chemical arsenal that rivals those of many snakes. Many of these poisons are familiar and they greatly exacerbate the blood loss caused by the dragon's bite. They cause internal haemorrhaging from leaky blood vessels, prevent blood from clotting and cause muscle contractions and paralysis. Fry calculated that a typical adult dragon would need only 4mg of venom proteins to send a 40kg deer into toxic shock from collapsing blood pressure. A full venom gland packs at least eight times this amount.
If the dragon has venom, you can be sure that it uses it. Venom is so costly to produce that the moment it becomes obsolete, natural selection rapidly does away with it. That's happened in other reptiles - members of venomous families that have developed other ways of feeding (like constriction, or egg-eating) quickly lost their venom system. The glands atrophied, the fangs became smaller and the genes that produce toxic proteins built up debilitating mutations. The Komodo dragon, on the other hand, has strong glands that are loaded with poison. |
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Uncertainty may make you uncomfortable. Certainty makes you ridiculous.
Why not question something for a change?
Genetic Literacy Project |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 05/19/2009 : 14:01:30 [Permalink]
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I read that, and I am loosely acquainted with Dr. Fry, or was some years back when I was active. He is an excellent herpetologist and one of the world's top venom men. But I'm withholding opinion on this.
The fact that these lizards have a toxic saliva shouldn't come as a surprise; it is quite common. However, the delivery system is not sophisticated and, If I understand the article, large quantities would be iffy to deliver.
Adult komodos hunt large animals such as deer, swine, and even water buffalo -- it takes a hell of a jolt to put one of these down with venom alone unless the blood loss is extreme. In my tentative opinion, it is often a combination of the venom and the bacterial infection. The question is; how effective is the venom as compared to the sepsis caused by the bacteria?
This is a fascinating study and I await more info.
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist! 
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Zandermann
Skeptic Friend
USA
431 Posts |
Posted - 05/19/2009 : 16:41:51 [Permalink]
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Seems to me that a Komodo wouldn't need much in the way of venom -- what with its size and jaw strength on its side.
Interesting though that it isn't just bad oral hygiene that takes down its prey |
"If in the last few years you haven't discarded a major opinion or acquired a new one, check your pulse. You may be dead." |
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Hawks
SFN Regular
Canada
1383 Posts |
Posted - 05/20/2009 : 06:47:29 [Permalink]
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Would there really be strong selection against losing venom in the case of Komodo dragons (if they have any)? Somehow I got the idea that they bite, the prey runs away, and the dragon that bit MAY be the one finding a tasty meal (rather than another dragon stumbling across it).
As an aside: I saw one of these up close (from a couple of meters) in the wild on the island of Rinca some ten years ago. I suppose the ranger that was guiding us knew what he was doing when taking us that close... |
METHINKS IT IS LIKE A WEASEL
It's a small, off-duty czechoslovakian traffic warden! |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 05/20/2009 : 07:20:52 [Permalink]
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Originally posted by Hawks
Would there really be strong selection against losing venom in the case of Komodo dragons (if they have any)? Somehow I got the idea that they bite, the prey runs away, and the dragon that bit MAY be the one finding a tasty meal (rather than another dragon stumbling across it).
As an aside: I saw one of these up close (from a couple of meters) in the wild on the island of Rinca some ten years ago. I suppose the ranger that was guiding us knew what he was doing when taking us that close...
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I am all but chartreuse with envy!
This is entirely true. The early lizard might get the bite but not the meal especially if it is a smaller specimen. However, communal feeding is common if the animals are about the same size.
Venom has been selected against only in species such as constrictors, which have developed an effective alternate feeding method. Otherwise, venom, even in it's mildest form, is just too handy an asset to give up.
However, it is interesting to note that in Heloderma, the venom is mostly used for defense and is way stronger than necessary for subduing it's normal prey. It will put a strong man on the floor in short order, although, to my knowledge, there has never been a human fatality from them.
I love venomous animals! They are just so unique; so fascinating. And there is so much more to learn about them.
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist!
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Komodo Dragon has more than a dirty mouth.
