Opossums Immune to Poisons

Piccolo Namek/Creative Commons

This fascinating (and entertaining) article explains how Virginia opossums were found to be immune to many venoms, including those produced by cobras and other animals they never encounter, as well as toxins like ricin. Scientists have isolated the toxin-killing agent in the possum and hope to turn it into a universal antidote humans can use. They've already proved it can confer immunity on rats. 


What are Opossums? ‹ Bittel Me This 

"We’re talking timber rattlers, cottonmouths, Russell’s vipers and common Asiatic cobras. We know this because scientists rounded up a bunch of nasties and forced them to bite a bunch of unfortunate opossums, the latter of which responded like it was a mild bee sting. "

Update: In another interesting venom-related story, scientists have found scorpion venom kills MRSA, the notorious drug-resistant strain of Staph, as well as other resistant bacteria. Findings like this are one reason for preserving species: nature has already solved a lot of the chemistry problems we'll soon be facing. 


Thanks to Erin for the tip.

13 comments:

  1. They can tangle with Cobra's...provided they aren't mounted on a Ford Mustang.
    Do you know why the Chicken crossed the road? To show those crazy Possums it can be done!
    (Dee)

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  2. Good one. (Although now that I live in the North, I see more deer as roadkill.)

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  3. Like the spotted hyena--another fascinating animal with an incredibly ugly demeanor and a serious creep quotient. In both cases, it doesn't seem to help that the default facial expression is a sort of leering grin.

    A lot of people compare opossums to rats, but I don't really see it--apart from the gray coloring and naked tail. The way a rat moves is different, for one thing--much more agile and squirrellike than the way an opossum just sort of barrels along when hurrying. (Also, no Norway rat gets as big as an opossum--it's illusion or booze talking when someone tells you different.) They do, however, remind me a lot of the primitive insectivores known as "moonrats" which in some ways appear to exploit the niche of the opossum in their home range.

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    1. Would be interesting to know if moonrats too are immune against snake venom. I figure if they forage close to the ground, in dry leaves and under dead logs this may mean frequent encounters with snakes...

      I also find it very intriguing that opossums are immune to cobra venom. Is it perhaps because coral snakes (which belong to the same family) have a similar composition to their venom and are encountered by opossums? I've also read an interesting theory which says at least one species of cobra may have existed in North America in prehistoric times, thus explaining, for example, the hog nosed snake's cobra-like defensive display, although to be fair, quite a few snakes, including colubrids and elapids, have hoods as well...

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    2. The trouble with that line of reasoning is that the SAME COMPONENT confers immunity not only to monocled cobra venom, but also to the venoms of Russell's viper, the Western diamondback rattlesnake, the taipan, Stokes's sea snake, the fat-tailed scorpion, and the honey bee; plus, it neutralizes a toxin derived from castor beans (ricin). Even if we can place some close relative of this cobra in the possum's evolutionary history, we can't do the same for all of these very different organisms. I think this means that possums developed this component in response to some very limited set of toxins in its environment, and it fortuitously happens to work on lots of other stuff. That's just a mind-boggling thought, but I'm having trouble seeing a better answer here. Maybe a biochemist could shed more light on this.

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    3. Croconut will already know this, but for the benefit of the non-herpers, I should add that those venomous snakes represent several different families, some not closely related at all.

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    4. Taipan and sea snake as well? Hats off to the opossum.

      The honey badger too is resistant to the venom of such nasty characters as the puff adder, the mamba and the cobra. I wonder how it compares to the opossum.

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    5. Honey badgers are just amazing in many ways!

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  4. James, I suspect most people don't hang around long enough to notice the locomotion! My experience is that the possum doesn't move unless it wants to, whereas the rat runs away readily (though I've read about times when they didn't).

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    1. Very true--they don't really seem to be concerned with people. In fact, they tend to really make themselves at home if given the slightest encouragement. My parents, who grew up during the WWII era, mention that they never used to see them in northern NYS as kids; my father's first sighting was when he was in the Army stationed at Fort Dix, NJ, and a dead one showed up on the base. Now they're extremely common, I sometimes see as many as three or four dead ones along, say, a five-mile stretch--and you're almost guaranteed a sighting of a live one if you know where to drive at night.

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  5. We sat out a live trap in hopes of catching the raccoon that killed off all of our Koi. We caught a possum instead. And he did indeed fool me, I thought he was dead. He was lying all balled up, flies were swarming over him. We even poked at him several times to see if he was just 'playing possum'. When Shawn opened the cage to dump him over in a box for disposal, he came very much to life. Scared the devil out of me.(Dee)

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  6. I hadn't even thought of flies treating them as dead. That's interesting.

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    1. I think it has some to do with the rotten-smelling fluid they produce when playing dead. That's what I call commitment to acting...

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