venemous colubrid question

[rwg]

It seems Dr. Fry's research on colubrids is circulating since in the last 2 weeks I have heard that "all colubrids are venemous" and that "all snakes are venemous", although in both cases it was stated that the venom was so weak as to not pose a threat. For the purpose of correcting this misinformation, I was wondering if Dr. Fry or anyone familliar with his findings could run down the colubrids known to be non-venemous. As I understand it, it's a majority of North American colubrids right? I list of major genuses or species would be helpful.

rg

[psilocybe]

The current idea is that all colubrids with the exception of a few north american genera (Pituophis, Lampropeltis, and a few others) are indeed venomous, meaning that they have toxins in their saliva. The degree to which they can envenomate is questionable, and it's unlikely you'll have to worry about a water snake bite anytime soon! They simply don't have an effective delivery system of the venom (even as effective as rear-fangs). So a true envenomation is pretty unlikely. Remember though, only a few decades ago boomslangs (Dispholidus typus) were considered harmless! Now of course, all snakes are not venomous. Boas, pythons, and probably all of the basal snakes are non-venomous. Besides, Colubridae is the taxonomical dumping ground for snakes, and the family could really use a makeover. Hope some of this helps.

AP

[psilocybe]

Taken from venomdoc message boards, posted by BGF

Hi mate

The first thing to realise is that there is not one family of 'colubrids' but actually several genetically distinct families, some of which are far closer to cobras than to corn snakes. The 'Colubridae' family was a totally artificial dumping ground.

The duvernoy's gland was given to the venom gland in the colubrids before the relationships to the elapids and vipers was worked and before we discovered that the toxins put out are the same sorts put out by the elapids and also some of the same ancestral ones shared with the vipers. Therefore, the duvernoy's gland IS the elapid/viper venom gland and as such all the glands are simply referred to as venom gland, the term Duvernoy's gland has been totally abandoned.

Also the distinction between aglyphous (lacking fangs) and opisthoglyphous (rear-fanged) has also been dropped since it shoe-horned a large number of unrelated snakes into two artibrary and contrived distinctions.

Basically, there was a single origin of venom, way back when before the vipers even split off from the advanced snake tree (Colubroidea). There are a 8 toxin types shared amongst all the venomous snakes and the ancestral venom was quite potent. This makes perfect evolutionary sense since there could not be a strong selection pressure for the evolution of advanced fang architecture without something worth delivering. The first venomous snakes lacked fangs and indeed, even large rear-fangs are not necessary to deliver venom. I consulted on a significanly neurotoxic envenomation by the African cliff racer (Coluber rhodorachis) last year. The symptoms were basically death adder-lite.

In anycase, fangs were an improvement that came later, much as the voice box in the primate lineage came way after the evolution of the ability to make noise. In fact, advanced fangs in the snakes has evolved independently on at least four occassions.

As for whats in the 'colubrid' venoms, there is a trmendous diversity, as great as that between elapids and vipers. The Colubrinae family venoms are often packed full of 3FTx and are neurotoxic as all hell but this family also contains two of the most potently blood chemistry affecting venoms, the boomslang (Dispholidus typus) and the twig snake species (Thelotornis species). Little is known about the Natricinae family venoms clinically except for the Rhabdophis genus which has a devastating (but unrelated to the boomslang and twig snake) action upon the blood. In the other families, even less is known clinically but we found the venoms to be typically just as complex as an elapid venom. The Psammophiinae family species Psammophis mossambicus in particular.

Some of these snakes had very small venom glands others huge, even within the same family (in the Colubrinae, the radiated rat snake (Coelognathus radiatus) had a pretty small venom gland while the egyptian catsnake (Telescopus dhara) had glands even bigger than a lot of elapids. In the Psammophiinae family, Psammophis mossambicus (olive sand snake) had huge glands as well.

SO, is there anything as a non-venomous colubrid? With the exception of the North American clade of Lampropeltis/Patherophis/Pituophis and some relatives, the answer is no. Are all of them dangerous? Certainly not. Are there lethal ones in there we don't know about? Definately. This has already happened in the past, with Rhabdophis species being some of the most popular snakes on the US/European pet trade in the late 70s/early 80s until a few kids bled out of every orifice after picking one up at the local pet store. Oops!


Go to the publications section of my webpage and download the articles that are there. We have two more coming out soon, one on the very first 3FTx every isolated from the venom of anything but an elapid. We isolated this from Coelognathus radiatus and called the toxin alpha-colubritoxin. It is not different than a comparable elapid 3FTx. Same mode of action, same potency and the 3FTx are present in pretty much all the 'colubrid' venoms. This is in the October issue of the Journal of Molecular Evolution. We published this before we obtained more evidence regarding the single origin of venom, consequently we still call the gland the Duvernoy's gland. We didn't formally get rid of it until the LC/MS article where we had more evidence (its best to do things conservatively like this so that when a major change is proposed, its has more supporting data). However, due to the nuances of relative publication speed, the alpha-colubritoxin paper is actually coming out after the LC/MS paper. The other article coming out soon is one where we worked out what was in the venom of the very first venomous snake. This one will be out in Molecular Biology & Evolution sometime early next year.

After what Wolfgang and I have pulled out of our hats over the last two years, the herp books need to be rewritten Ah well, guess we'll just have to write our own

Cheers
B
_________________
Dr. Bryan Grieg Fry
Australian Venom Research Unit

GENETIC ENGINEERING: Tampering with chromosomes so that science might develop a new miracle cure or a rabbit that plays the banjo.

X-CHROMOSOME: A genetic double-cross that empowers women with the ability to bear children and reserves for men the right to be color-blind hemophiliacs.


http://www.venomdoc.com


AP

[rwg]

Thanks AP,

I stumbled onto that thread a little while after posting here. I followed up there asking for a little clarification on what is meant by "the North American clade of Lampropeltis/Patherophis/Pituophis and some relatives". I'll post back here what I learn for any who dont read both forums and may be interested.

rg

[Gary O]

Dr. Fry's articles are addictive. i love them and visit his site more then once a day lol