Evolution in colubrids

[Dr. Bryan Fry]

I have to agree, anyone who knows me will agree that in addition to being smitten by snakes, I'm also a complete computer geek ;-) My addiction to the internet drives my wife to distraction, I've even managed to track down an internet connection while on remote islands in Asia ;-p Lasted three days before I cracked and went searching!

Cheers
B

[Dr. Bryan Fry]

PS

I'm writing this while at the very tip of Cape York in Queensland Australia, we've been here for a week and a half now catching sea snakes. Always too much fun ;-)

Cheers
B

[HetForHuman]

that sounds like fun, i wish i could join you.

[Jeff_Favelle]

Cape York? Go get me some new maculosa bloood man!! And then head south and pick up some Womas!

Cheque is in the mail.............

[Lisa]

Three thoughts.
Dr Fry, I would have expected you to have a portable sat hook up or something I hear you on the addiction thing. katey considers my laptop be be the "other woman"

Where else but herping do you get to do stuff like rock climbing, scuba diving, get a tan, etc.

I'm looking forward to seeing the rest of the papers. What's next for colubrids? A delivery system?

I'm not too concerned about this causing the banning of snakes. As Dr Fry said, there are some colubrids with out any venom glands and the ones that do carry venom are technicaly already banned where venomous snakes are already banned, which here in ontario depends on your location (it seems if you want to live in a big city here you have to give up your venomous snakes). There's still lots of snakes to play with. Learn the laws of your area. Do you want a cobra in your collection? How about a colubrid that's as leathal as a cobra? Would you let just anyone have access to same said cobra? Then why is it so important to keep a snake that is as potentialy leathal (if not more due to the lack of antivenom)? Remember not all Colubrid snakes are venomous, just some of them. And this doesn't affect boids either (though they seem to have a bad rap in parts of Canada, maybe because we don't have any native to the country). I don't have a problem with people keeping venomous snakes, as long as they're properly housed and not against the law.

[Scales Zoo]

Hello Dr. Fry.

Nice to see you on ssnakess.com - I hope you stay!

Midwest rocks, we've been pushing it here in Western Canada for over a year.

I am very interested in the developements of the venoms associated with colubrids. We live in an area where there are 3 types of garter snakes. Their bites really itch for a long time, or so I have heard.

We also keep quite a few different asian elaphe, and other non typical ratsnakes.

We do many educational shows, and I am suprised how many times I am asked about garter and hognose "venom". I always like to have a very informative answer.

Have you studied these species?

Regardless, you have an open invitation to visit the zoo, our home collection, the rattlesnake hibernacula 12 kms from our back dore (Northern most rattlesnakes in the world), and have the chance to find many garters and a few hoggies possibly.

Keep up the good work Dr.

Ryan and Sheila

[Simon R. Sansom]

Dr. Fry;

Have you looked at any boids in your study?
The reason that I ask is because I seem to be fairly sensitive to snake "saliva".
When I get bitten I USUALLY get the swelling, itching, welts, etc. My most annoying bite was actually from a friend's Candoia carinata (Roy, if you're reading this, remember the "Flying carinata" incident? LOL!). The itching and swelling lasted for five days. It was actually worse than a Thamnophis bite, which I suffered just a couple of weeks prior. The Candoia bite was just a VERY quick, defensive nip, whereas the Thamnophis hung on and chewed for a good five minutes, yet the symptoms from the Garter bite went away after about twenty minutes as is usual. The Candoia bite left my knuckle swollen, red, itchy and with white, puffy marks around each tooth-hole.

Can you shed any light on this for me? I assume that I'm just sensitive to certain components of the saliva??

Thank you.

Simon

[Dr. Bryan Fry]

Hi mate

Have you had a chance to check out the article? I've uploaded it and you can download it at
http://www.venomdoc.com/downloads/BG...oidea_RCMS.pdf

Basically it means that venom evolved only once, over a hundred million years ago. This was before any of the lineages of the Colubroidea (advanced snakes) we even thinkl of (elapids, vipers, atractaspids, colubrines, natricines, etc.) even existed. The vipers were the first to split off but the venom gland already existed and already contained a potent venom. This was before any fangs showed up. It makes sense. Evolution does one thing at a time.

First a potent, complex venom that is delivered through sharp, evenly sized teeth. Then comes a more refined delivery mechanism. Can't do both at the same time and a complex delivery mechanism certainly evolve if there was nothing to deliver. So, efficient fangs came after the venom. One thing drives another. Just as the ability to make noise in the primates drove the development of our voice box.

These ancestral half a dozen toxin types we worked out, made for quite a complex mitures with potent activities. The snakes have been refining them ever sense. Some toxin types have appeared at different point in the evolutionary tree. We discovered that all the 'colubrid' lineages contain in their venom the same sorts of toxins as a cobra or mamba. We isolated from the venom of the radiated ratsnake (the archetypal 'non-venomous' snake) a 3FTx (three-finger toxin), the typical cobra-style toxin. As is the common actiivity of 3FTx, this toxin was a potent neurotoxin. Thus, these very potent neurotoxins were evolved after the vipers split off from the main evolutionary tree but before any of the various 'colubrid' lineages. These toxins however are just as potent as the homologous toxins found in death adder or krait venoms. Some of the crude venoms are scarily toxic (some Boigas are as toxic as any elapid). Some of the snakes have huge venom glands as well (the ones in Telescopus and Psammophis are truly scary. As big as any elapid and more so than many.)

So, the venom predated the different 'colubrids' and all the 'colubrids' contain actual venom. The idea of the Duvernoy's gland is toast. Same venom, same gland.

However, one lineage has recently lost the gland and reverted back to the more primative, adept constricters. The American 'Elaphe-type' i.e. Pantherophis, Pituouphis, Lampropeltis, share a common ancestor. This snake was venomous but with small yields and not exactly the world's most brilliant delivery system. This snake didn't really constrict that much but instead bit the hell out of the prey ala the Asian Elaphe. This lineage also fed on amphibians and reptiles.

The American 'Elaphe-types' made the switch from amphibians/reptiles to feeding on rodents. The venom system wasn't up to scratch for rodents but constricting did the job quite nicely. The Lyre snakes (Trimorphodon) are a good example of an American split that stayed venomous. The Central American lineages stayed nicely venomous and several lethal ones are in there (i.e. Philodryas).

Even Coluber have been known to deliver a nasty bite, I consulted on a pet store bite to an employee who was nicely paralysed by the bite from an Egyptian Coluber.

So, are the vast majority of the colubrids venomous? Yes.
Are all dangerous? Yes.
Have dangerous ones previously been sold as harmless? Yes (e.g. Rhabdophis in the late 70s and early 80s or Psammophis in pet shops now).
Are all the known lethal ones related or scattered liberally across the taxonomical tree? The lethal species have been seemingly by random, all the seven 'colubrid' families have had at least one genera shown to be capable of severe envenonomations.
Are there lethal species yet to be known? Definately.

The truly scary part is that non of the existing antivenoms are likely to touch any of the colubrid venoms. So while they may be less likely to get you, if they do you are screwed.

I'd love to come up, I haven't been to North America much for the last ten years. Certainly never have been to Canada. However, no idea when I'll be up that way. I am going to try for the next years Daytona show. I went a couple years ago and had a blast.

Cheers
B

[Dr. Bryan Fry]

Hi Simon,

We did look at the saliva of the reticulated python. No proteins in there at all. The saliva is full of mucous and this stuff could of course be irritating as hell. The worst of course is when those long brittle teeth break off in your flesh. Always truly sucks.

Cheers
B

[Simon R. Sansom]

Thanks, Doc! Very interesting.
Yes, I once had a Carpet Python tooth in one of my hands for over a year before it worked it's way out!

Simon

[Janiman]

Dr Fry,

I'm very curious about the potential for delivering these toxins. Where do the toxins vent into the mouth (saliva glands or another route?), and does it take a conscious effort by the snake to excrete it or is it present in the mouth/saliva at all times?

Thanks for such a fascinating thread,
F

[Dr. Bryan Fry]

Hi Jaiman,

In some species there is a well developed opening in the back of the mounth and a few enlarged teeth poking out (ie Leiheterodon). In others its much less developed (ie. radiated ratsnakes). Some alternate arrangements seem to be in development (ie Psammophis seems to be dumping venom forward as well as back). Some have muscles attached to the venom gland (e.g. Mehelya) which is the next refinement level up.


The distinctions 'aglyphous' and 'opistoglyphous' are totally artificial distinctions and are dropped. Similarily abandoned is the very concept of the 'duvernoy's gland. Also 'colubrid' is not longer the taxonomical dumping ground for anything that is not obviously a viper or elapid, when in fact there are seven very distinct families in the 'colubrids', some of which are vastly more closely related to a cobra than to a cornsnake.

Cheers
B

[BWSmith]

I have not even begun to read this thread yet, just got back in town a couple hours ago. I just have to say:

Princess White Devil is Everywhere I turn!!!!!!

How goes it mate?

[Simon R. Sansom]

Dr.Fry, which snakes are considered to be the most advanced/modern?.

Simon

[Dr. Bryan Fry]

BW!!!! Are you just back from your wedding? If so, congrats mate ;-) And yes, I've been spending a bit of time online lately ;-p

Simon, as for which snakes are considered the most modern, thats a good Q and depends on what you define as modern. While the Viperidae are the most ancient of splits in the advanced snakes (Colubroidea), they haven't just been killing time since then. The fang architecture and the Crotalidae clade's heat seeking pits certainly make them tremendously advanced.

On the venom side of things, the Australian elapids have been the busiest in recent times, with the recent development of many new toxin lineages (as well as the remarkable streamlining of the sea snakes venoms). So, based upon recent high level of evolution and novelty of groups, I'd say that the Australian elapids have the most advanced venom. However, while the mambas have been quite stingy in the development of new toxin groups, they have taken the 3FTx (three-finger toxins) into a truly different arena.

At the end of the day, I'd break it down this way:

Most advanced fang architecture - vipers although the Atractaspis fangs are pretty trippy and just as advanced. On the elapid side, the death adders have the most highly evolved fangs of any elapid, actually being semi-mobile in a viper-like way. Of the 'colubrids' the boomslang certainly takes the prize.
Most advanced venom glands - Either the Atractaspis venom glands or the Calliophis bivirgata venom glands (both have evolved new glands that connect behind the normal gland and run up to 1/3 the length of their body).
Most highly refined venom (taking old toxin types and turning them into an art form) - Dendroaspis (Mambas)
Most novel venom (evolving potent new toxin types) - The Australian terrestrial elapids, they have quite a few new toxin types, including new ways to completely screw up your blood.
Most advanced genetically - this is still being worked out.

All the best
B