Reptile & Amphibian Forums

I remember someone saying in a thread a while ago that heterodon teeth are no longer believed to be used for popping toads. I though little of it at the time but today I was reading about it in a book. Book said the teeth are used to pop lungs and create a slit for venom to flow. Is that true?

Or are the teeth simply a means of getting venom in, weakening the toad and it then deflates on it's own. That would seem more likely to me, I'd think it'd be tough to puncture both lungs with any real consistancy, especually with different sizes of toad.

Does the venom actually flow through the tooth as in a viper or elapid or do the ducts simply deposit it in the mouth and allow it to mix with the saliva?

If the venom does mix with the saliva, is the venom always of the same concentration or does the snake only release it when foods on the way?

What type of venom is it? Symptoms?

Thank You
Cam Hanna
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"Way to breath! No breath"
-- Jimbo Jones

IMO the jury is still out on just what the function of these inlarged teeth is. They are not venom injecting fangs. Since a study was done on their diet and it was found that toads are only a part it. In some areas of their range toads are less than half of their diet. The idea that the teeth are for deflating toads has been discounted.

Hognose are venomous snakes. Capable of biting and deliviring venom. In a pretty negligiable ammount as that may be, they are venemous snakes.

Relative to elapids and pitvipers, they do not have the adaptations for injecting venom deep into tissue. The paper I cited made a pretty good case for the enlarged teeth being used primarily for holding struggling live prey. So... I would not say that Tim's statement was entirely incorrect.
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...the oldest task in human history: to live on a piece of land without spoiling it."
Aldo Leopold (1938)

"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
Calvin and Hobbes (Scientific Progress Goes 'Boink', 1991)

Hi mate

>>Relative to elapids and pitvipers, they do not have the adaptations for injecting venom deep into tissue.

Of course not. Highly developed fangs were an additional improvement that came after the evolution of venom, and such fangs have evolved at least four times on separate occasions. The enlarged teeth were an improvement over normal teeth and facilitate the venom by creating deeper wounds. Grooving was a subsequent improvement to help channel the venom and hollow hypodermic needle fangs the ultimate adaptation.

Evolution of the venomous snakes could be viewed as:

1. Venom - the obvious first step and happened only one time (which is why the term 'Duvernoy's gland' to distinguish 'colubrid' venom glands from elapid or viper homologs, has been abandoned and venom gland used in all cases).
2. Enlarged teeth - quite variable as to which and evolving on quite a number of occasions, this is why aglyph and opisthoglyph are artificial distinctions that shoe-horn a unrelated snakes into entirely contrived distinctions.
3. Grooved teeth - yet again quite variable and independently evolving on numerous occassions.
4. Hollow fangs - variable yet again. The elapid fangs are unrelated to the viper fangs and the Atractaspidae fangs appear to be a third evolution. The highly mobile and extremely advanced boomslang fangs, while not hollow are deeply grooved and represent a fourth evolution of advanced architecture.

> The paper I cited made a pretty good case for the enlarged teeth being used primarily for holding struggling live prey.

The paper you are referring to was written before the relationship of the venoms of the various 'colubrid' families in relation to the atractaspids/elapids/viperids was worked out. This is not to say that large teeth are not useful in holding prey but they are more likely to be enlarged ones in the front of the mouth rather than tucked all the way in the back (ie the large front teeth in Ahaetulla species).

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

www.venomdoc.com

What a great post, I really appreciate the breakdown on the evolution of venomous snakes! I just got done reading your post on the rear fanged forum about preaching to the "Flat Earth Society" about Hognoses and venom. In order to keep you from having to come back to this forum and wear out your fingers typing the same things over and over again, I figured we would spell things out and lay down the law right here.

Hognoses are venomous.
Hognoses have true venom glands that produce venom, not just "toxic saliva".
Hognoses have enlarged teeth for facilitating venom injection, but usually requires mastication.
Hognose's enlarged teeth do not deflate the lungs of toads, as their enlarged teeth were primarily developed for venom injection.
Hognose's enlarged teeth play a secondary role in restraining struggling, and slippery live prey.
Hognoses are not dangerous.
Hognose bites have not been responsible for any published cases of hospitalizations for the treatment of bites, much less any deaths, amputations, or other debilitation's associated with the bite.
Hognose bites are almost entirely the result of feeding responses by careless behavior of the handler.
Hognoses are the cutest damn snakes ever.

Hopefully this list can be copied and pasted into future discussions. If you have anything to add, let me know.
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...the oldest task in human history: to live on a piece of land without spoiling it."
Aldo Leopold (1938)

"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
Calvin and Hobbes (Scientific Progress Goes 'Boink', 1991)

If hognoses and bush vipers had a cuteness fight, I'm not sure I know who would win.
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"The serpent crams itself with animal life that is often warm and vibrant, to prolong an existence in which we detect no joy and no emotion. It reveals the depth to which evolution can sink when it takes the downward path and strips animals to the irreducible minimum able to perpetuate a predatory life in its naked horror."
Alexander Skutch

Very nice synopsis And yes, they are extraordinarily cute snakes. However, those no-necked little buggers were a pain to milk, they seemed to just tuck their head into their body

Cheers
Bryan

Since I will probably never get to talk to someone who has actually milked a hognose, can you describe what it is like? They have ridiculously small venom glands, you must not be able to get much out of them!
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...the oldest task in human history: to live on a piece of land without spoiling it."
Aldo Leopold (1938)

"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
Calvin and Hobbes (Scientific Progress Goes 'Boink', 1991)

We milked them the way we milked most of the other 'colubrids': knocked them out with zoletil, hit them with pilocarpine (to stimulate the release of the venom from the protein secreting cells, then injected atropin to reverse the pilocarpine effects (this lent itself of course to lots of lines from Pulp Fiction ). All up, it takes about a half hour a snake. We were doing ten snakes a day of various species, seven days a week for eight months. Back breaking work but the results were of course worth it

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

www.venomdoc.com

If your going to quote someone in your post title how about getting it right. I said the enlarged teeth are not venom injecting fangs. I didn't make a statement one way or the other about the venom of Hognose snakes. I have seen no definitive study about the use of the aforementioned enlarged teeth. If you have seen or conducted such a study please point me to it.

Enlarged teeth is discussed very well in Dennis Desmond's web site, http://www.hognose.com/pages/venomous.htm#venomous

I would like to add some information to his article. I recently attained an excellent publication (Witwer, M.T. 1995. Heterodon and other not-so-harmless "harmless" snakes. Journal of the Northern Ohio Association of Herpetologists. 16 (1):12-20. ), that addresses much of what you're asking.

Tooth morphology in this genus is described, the rear teeth are latterly flattened and are ungrooved. All that it says about how the venom is delivered is that the tubules lead into a duct which opens in the vicinity of the posterior maxillary teeth. So it is probably more like what you said, it just mixes with the saliva and seeps in. What are the main purposes of the enlarged teeth? During swallowing, the enlarged rear teeth contact the prey item first. It is obvious to see that the teeth are meant for holding the prey item, especially since they do not constrict, nor is their venom really strong enough to subdue their prey within a short period of time. They must rely on their teeth to hold the prey in place until they tire. The author also claims that since they have longer teeth instead of having a greater number of equally teeth, this means there is a greater bite force concentrated at the point of contact, thereby increasing the penetrating capabilities. This may be especially beneficial if the prey is inherently difficult to grep such as the frogs and toads they are famous for!

As far as toad popping, the jaws of Heterodon are strong enough to deflate toads without the benefit of enlarged teeth. It has been nearly 30 years since there was research done on the length of the enlarged teeth that determined they are not long enough to puncture a toad's lungs, unless the toads were swallowed belly up. This is a classic case of a myth being perpetuated incessantly through the Internet and without any real research being done on the topic.

I hope this helps!
click here for the link

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...the oldest task in human history: to live on a piece of land without spoiling it."
Aldo Leopold (1938)

"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
Calvin and Hobbes (Scientific Progress Goes 'Boink', 1991)