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I was recently having a discussion on venom properties when the other party mentioned a "Neurotoxic trend" happening in the EDB. I'm curious what the consensus is: Does venom evolve slowly over millions of years or does it take an evolutionary leap as some scientists are pointing to in other species adaptations? Thanks.
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Amor et Lux,
Ron

"The gods tolerate the human race for no other reason than our talent for bullsh1t. It's the only thing about us that doesn't bore them to tears" Tom Robbins "Villa Incognito"

>>I was recently having a discussion on venom properties when the other party mentioned a "Neurotoxic trend" happening in the EDB. I'm curious what the consensus is: Does venom evolve slowly over millions of years or does it take an evolutionary leap as some scientists are pointing to in other species adaptations? Thanks.

There are a number of different aspects to venom evolution - this is not a simple concept. First of all, it is important to realise that venom is a cocktal of dozens of different toxins. "Venom evolution" can refer to the evolution of individual toxins, or to changes in the extent to which different toxins are represented in the venom.

Venom composition can evolve quickly, probably largely by changes in gene expression.

So, for instance, all eastern diamondbacks probably have the genes for these neurotoxins, but most don't secrete them, at least not in sufficient quantities to make much of a difference n human bite cases. At the same time, if you are referring to a recent magazine article in which it is claimed that a number of species of rattlesnake are rapidly turning neurotoxic as we watch (based on a few observed cases with neurotoxic envenomation - a clear case of adding 2 and 2 and getting approximately 534,267), then that is nonsense, and based on total, abject ignorance of even the most basic ideas of genetics and evolutionary biology.

The toxins themselves also seem to evolve relatively quickly (on an evolutionary timescale), but I would not describe it as sudden "leaps".

Hope this helps.

Cheers,

WW
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WW Home

Thanks, it actually helps alot but still leaves me with the question of what is "relatively quickly on an evolutionary timescale". For instance could a species that primarily utilizes hemotoxic components in it's venom now have been primarily neurotoxic 3-4,000 years ago? Or could a species that exhibits very little toxicity now have been considered deadly by earlier civilizations and visa versa? Thanks.
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Amor et Lux,
Ron

"The gods tolerate the human race for no other reason than our talent for bullsh1t. It's the only thing about us that doesn't bore them to tears" Tom Robbins "Villa Incognito"

A good friend who extracts & processes venom for a living told me that the venom of C. adamanteus in northern Florida is considerably more potent than that of animals from further south. Not sure if this adds anything to the discussion or not.
I think my point is that toxicity within a species can vary greatly. Whether that has anything to do with evolution or not is for brighter minds than mine to sort out.

~~Greg~~

The key here is that with new habitat encrouchment (read: habitat destruction), populations that were seldom encountered become medically important in short periods of time. The best example of this is in California where populations of C. oreganus helleri with extremely neurotoxic venom are now causing quite a few envenomations. The neurotoxins have always been there but the victims haven't. Similarly, with more medical awareness and venom research being conducted, the envenomation pathology and venom profiles are being better documented and characterised.

The type IIA PLA2 toxins found in viper venoms were evolved at the base of the Viperidae tree and the neurotoxic activity was developed prior to the major radiations. So, neurotoxic PLA2 have been isolated from such disparate genera as Crotalus, Trimeresurus and Vipera. Hardly a case of a big leap in venom. Therefore, all the viper venoms contain these sorts of toxins but the relative expression level can vary from trace amounts all the way up to being the dominant toxins present. This can happen not only between genera, or between species but even within geographical variations of a particular species.

Cheers
Bryan
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Dr. Bryan Grieg Fry
Deputy Director
Australian Venom Research Unit
University of Melbourne

www.venomdoc.com