Reptile & Amphibian Forums

Greetings all, time to accept the change & start posting again...
The Duvernoys gland seems to be as much a cauldron for toxicity as the other venom glands. Necropsys I've done on ophidian prey from Diadophis (ringneck), Hypsiglena (nite), Clelia (musurrana), Trimorphodon (lyre), all indicate widespread hemolytic action with as little as 5-8 min. chewing. I would avoid a deep bite from all. Remember 2 well known herpetologists have been lost to colubrid bites!
Cheers & beers; jg

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Re: A small note, Wolfgang.. More..

Posted by Matthew Scruggs on November 26, 1999 at 12:38:36:

In Reply to: Re: I want the truth on this matter. posted by Wolfgang Wuster on November 26, 1999 at 03:22:17:

Wolfgang,

I've heard rumors of one Thamnophis bite serious enough to require brief (overnight?) hospitalization, but cannot confirm. However, given the kinship with asian keelbacks, I'm looking at T. sirtalis with a hint of respect.
Also, Ernst & Zug (not sure if that's right) inicate Diadophis has marked at least one mild reaction in humans, however, efforts to track this down have also been futile to date..

Cheers & happy holidays.

Genera of rearfanged and nonvenomous snakes
known to produce "toxic" saliva

Ahaetulla - Asian (vine snakes)
Alsophis - South American and West Indian ("racers"
Amplorhinus - Africa
Boiga - Cat snakes, mangrove snakes, brown tree snake, etc.
Cerberus - Asia (dog-faced water snake)
Clelia - South America
Coluber - Asia, Europe (racers)*
Coniophanes - Central and South America
Conophis - Central and South America
Crotaphopeltis - Subsaharan Africa
Dendrelaphis - Australasian (vine snakes)
Diadophis - North American (ringneck snakes)
Dipsadoboa - Africa
Dispholidus - Subsaharan Africa (boomslangs)
Dryadophis
Elapomorphus - South America
Enhydris - Australasian (water snake)
Erythrolamprus - South America
Heterodon - North American (hognose snakes)
Homoroselaps - South Africa
Hydrodynastes - South American (false water cobras)
Hypsiglena - North America (night snake)
Langaha - Madagascar (leaf-nosed snakes)
Leioheterodon - Madagascar (hognose snakes)
Leptodeira - South America (cat-eye snake)
Leptophis - South America (vine snakes)
Macrelaps - South Africa
Madagascarophis - Madagascar
Malpolon - Europe and Asia (montpellier snakes)
Oxybelis - South America (vine snakes)
Philodryas - South America (whipsnakes)
Pliocercus - South America (false coral snakes)
Psammophis - Africa and Asia (sand or grass snakes)
Psammophylax - Africa
Rhabdophis - Asia (keelback snake, yamakagashi)
Stegonotus - Australia
Stenorrhina - South America
Tachymenis - South America
Telescopus - Africa and Asia
Thamnophis - North and South America (garter snakes)
Thelotornis - Africa (bird snakes, twig snakes)
Trimorphodon - North and Central America (lyre snakes)
Xenodon

Possible, but unconfirmed:

Spalerosophis - Africa, Mid-East, Asia

*Keep in mind - I have never heard of a report of envenomation by North American racers. Most likely, Minton is referring to Asian or European species which are now considered to be in their own genera by herpetologists.
These are from Sherman Minton (1996), and other papers I've come across.

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: I will give these a shot:

: : Q: Is a snake with a mildly toxic saliva the same thing as mildly venomous?

: In rear-fanged snakes, it is not the saliva that is toxic. Many colubrids (a large number, in fact) have a special gland called Duvernoy's gland, which secretes venom. Although this probably evolved from a modified salivary gland, snakes with a Duvernoy's gland do have "normal", unmodified salivary glands as well. The saliva routinely present in the snake's mouth is not venomous, only the secretion from Duvernoy's gland.

: : Q: Is there any truth to what I heard about the mildly venomous and rear fanged members of Thamnophis?

: All Natricines, including Thamnophis, have Duvernoy's gland. There have been a few cases of people developing mild localised envenomation after prolonged Thamnophis bites.

: : Q: What is the comparison of the venom/toxic saliva to that of Heterodon, Boiaga, and hyspeglena?

: Not sure about the direct toxicity. In snakes with Duvernoy's gland, the main factor determining the danger to man is the ability to actually get the venom into a person, and the quantity available. Some colubrids have very potent Duvernoy's gland secretions (on a par with various elapids or vipers), but they secrete so little, or have such difficulty actually injecting it, that they are, to all intents and purposes, harmless. I have never heard of anyone getting a non-trivial Hypsiglena bite. Heterodon and Thamnophis seem to be on a par, whereas at least some Boiga (esp. B. irregularis) are capable of causing more serious envenomation.

: : Q: What is the comaprison of the Rear Fang/enlarged Teeth to that of Heterodon?

: Not sure what you mean - are you referring to Thamnophis?

: : Q: Have there been any recorded fatalities that have occured from Thamnophis bites?

: No. All bites have been mild, with local swelling and pain.

: : Q: does the venom vary from Thamnophis species to species?

: Not really known. Recorded symptomatic bites have been from T. sirtalis and T. elegans.

: : II.

: : It was also brought to my attention that members of the Diadophis genus were also Rearfanged and venomous. It was also brought to my attention that they are starting to think that Diadophis is forming a kinship with Micrurus. I have never heard anything before this that would support this. This part II. of this post is in Q & A format as well for ease of answering.

: : Q; Is there truth behind what I heard about Diadophis being containing venom/mildly toxic saliva and rear fangs/enlarged teeth?

: That is correct, but they are nevertheless harmless to humans.

: : Q: Can sombody tell me if there is any truth behind what I heard abbout Diadophis forming a kinship with Micrurus?

: What kind of kinship???? They certainly do not hybridise, or anything like that. The only documented relationship between Micrurus and Diadophis that I can think of is a predator-prey relationship!

: : Q: If it is forming a kinship would that involve in the change of the venom components?

: : Q: Would this change in toxic components involve nerotoxic venom?

: : Q: What is the comparison of the current venom/mildly toxic saliva of Diadophis to that of Heterodon, Boiaga, Thamnophis (If Thamnophis falls under this category), and hyspeglena?

: I have never heard of a symptomatic Diadophis bite, so this genus would appear to be harmless.

: Hope this helps.

: Cheers,

: Wolfgang

Well the studies into the Duvernoy's gland is still being documented, making it a little more than dificult to determine which species to consider dangerous to humans. I'm not deep into the studies myself, just what I've picked up through the forums, articles, and speaking with others herpers like myself. I have taken a couple of accidental deep bites from my Leptophis ahaetulla, with no affects at all. No redness, localized tingling, extra bleeding, DEATH...just kidding on the last part of course. But I have no doubt that a lizard would be going through hell when bitten. The same can be said with my Ahaetulla prasina, though in my experience A. prasina, which much be taken into thought are more acurate strikers, always striking one the top of the head where the L. ahaetulla are more "bull-rush" artists, tend to overcome prey of equal size more rapidly then L. ahaetulla. I would love to be able to say more into other species, but not having the funding for personal acquiring of species, or collegiate studies, I cannot delve TOO far into other species as far as venom dosages and composition. Though I would be glad to discuss the issue further in order to increase what I know, and help spread this knowledge to others who may be thinking unknowingly about snakes with rear-fangs and Duvernoy's glands. My quest started with problems my wife was giving me about obtaining H. gigas because they were "False water COBRAS", and she was told that they were rear-fanged. And you know how some people can be! But lets see where we can go eh? Thanks.

Howdy all!
Although I am not a HOT herper, I am fascinated by this evolutionary characteristic in snakes, and I frequently read this and the other venomous forums. I have a couple of areas I am particularly interested in learning about. One is the Duvernoy's gland and the other is the Nuchal glands found in certain species, particularly Rhabdophis tigrinus. This gland apparently produces a secretion similar to the bufadienolide secretions found in Bufo toads.
I am sure I must seem very naive about this but I read two separate web sites relating to these things. The first site dealt with the Duvernoy's gland and stated that snakes that developed constriction later in their evolution kept their Duvernoys glands, including Kingsnakes and Ratsnakes, even though it is reduced in these species. Here is this link:

http://www.anapsid.org/duvernoygland.html

The second link discusses studies done on the Nuchal glands present in some snakes:

http://www.columbia.edu/~la202/CV/Myanmar_snake_bufadienolides_2001.pdf

I suppose the presence of a Bufo type gland in the neck of Rhabdophis tigrinus would not only make these snakes venomous, but poisonous as well, technically.
There is not a whole lot of information I can find to substantiate this or refute it. I was wondering if anyone here knows about these things.
Thanks,
Scott