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This is sort of in relation to Dr. Fry's article about venomous colubrids. I'm wondering is this similar or related to the documented anti-coagulant properties of the North American Water Snakes (Nerodia sp.)? I've been bitten by these snakes a few times and I can attest first hand to those properties. What I guess I'm trying to ask is where is the line drawn with an animal whos saliva has destructive properties and what we call a venom?

Hi mate

The term 'toxic saliva' was coined to describe some of the effects produced by bites from species within the various families of 'colubrids' but always with the caveat that biochemical data was needed to resolve the actual relationships (which is exactly what we've gone and done). All of the 'colubrids' are properly venomous since they contain the exact same sorts of toxins as found in elapids and vipers (as well as more recently evolved ones specific to one or more families). This is due to the single origin of snake venom, right at the very base of the Colubroidea (advanced snake) tree. We have a paper coming out shortly on this that shows that at least five but possibly up to eight of the well characterised elapid/viper toxins are ancestral and actually shared by all the advanced snakes. Thus, the Nerodia species are venomous rather than having 'toxic saliva'

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

www.venomdoc.com

Dr. Fry wrote:

"The term 'toxic saliva' was coined to describe some of the effects produced by bites from species within the various families of 'colubrids' but always with the caveat that biochemical data was needed to resolve the actual relationships (which is exactly what we've gone and done). All of the 'colubrids' are properly venomous since they contain the exact same sorts of toxins as found in elapids and vipers (as well as more recently evolved ones specific to one or more families)."

Me:
Dr. Fry is apparently using a medical definition of venom.

Dr. Kenneth Kardong explains:
'Within the medical literature, the term ‘‘venom’’ is applied very generally to any biological secretion that may, if introduced into a human, produce a health risk. Jellyfish to snails to snakes to shrews are included.[75,76] Even some plants may qualify as producing a venom.[48] Certainly it is prudent for the health community to do so. By labeling a secretion a venom, or the animal or plant producing it as venomous, this issues a public health warning.'

Me:
The medical definition of venom is thus very useful to any medical professional dealing with toxic substances. However, the medical definition of venom is different than the biological (evolutionary) definition, as

Dr. Kardong further explains:
'For biologists, with functional and evolutionary questions in mind, the medical definition of a venom is too broad to serve our purposes well. The simple medical equation, ‘‘if it is toxic, then it is a venom’’ would make humans, whose saliva is toxic, venomous animals. An oral secretion may have many properties-viscosity, yield, color, toxicity, enzymatic activity, to name a few. But properties alone, simple chemical characteristics, are not the same as the biological role of a secretion, how it functions to contribute to the survival of the snake. We might guess a biological role from a chemical property, but proper verification must come from laboratory simulations of feeding strategies or better, from actual field studies. Further, oral secretions, at least in snakes, serve multiple and separate biological roles. The multiple biological roles reflect the many environmental factors, and thus the many independent selective forces, affecting the evolution of the snake venom system. The term venom, applied to viperid and elapid snakes, and especially if applied to Duvernoy’s secretion, masks the multiple functions in which this complex secretion participates. To do so confounds the study of adaptive processes.[78]'

Me:
It is quite obvious that Dr. Fry and his colleagues are embracing a medical definition of venom. Therefore they are rather indiscriminantly labeling almost any toxic substance as venom, without regard to their biological role. Unfortunately for them, they are not publishing their papers in medical journals but biological journals. In fact, Dr. Fry and his colleagues are attempting to answer biological questions (origin, evolution, adaptation and function) in their study of the secretions of the snakes rather than chemical questions (structure, synthesis). In order not to be misleading and to deal with these biological questions properly, they should adhere to the biological definition of venom, not the medical definition.

Dr. Fry:
"This is due to the single origin of snake venom, right at the very base of the Colubroidea (advanced snake) tree. We have a paper coming out shortly on this that shows that at least five but possibly up to eight of the well characterised elapid/viper toxins are ancestral and actually shared by all the advanced snakes. Thus, the Nerodia species are venomous rather than having 'toxic saliva'

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

Me:
Unfortunately, because Dr. Fry is using the wrong (i.e. medical) definition of venom, his claim that "venom" evolved at the very base of the Colubroidea tree is not acceptable to biologists. Using Fry et al.'s definition of venom, human saliva can be considered venom. If so, then venom did not evolve at the base of the Colubroidea tree, venom in fact evolved at the base of the Amniota tree. That means not just all colubrids, but all mammals, birds, snakes, lizards, crocodilians, turtles, the Tuatara and all extinct dinosaurs are also venomous. In fact, since amphibians are venomous according to the medical definition used by Dr. Fry, venom in fact evolved at the base of the Tetrapoda tree!

Clearly there is no end to the absurdity of employing a medical definition in a biological study. If a biological definition of venom is used instead, then it is quite clear that venom evolved once in the viperids, a second time in the elapids and a few more times independently in the colubrids.

Dr. Kardong:
"Further, there is now evidence that snakes and their prey are in a kind of ‘‘arms race’’. Prey evolve resistance to venom toxins; snakes evolve new toxins, and back and forth.[71 – 74] Simple genetic systems in snakes permit production of quite variable venoms (Slowinski, personal comm.). As a consequence, venoms may be variable within a species, and even within the same population through time."

Me:
The "simple genetic systems" to which Dr. Kardong allude may permit the independent evolution of venom in multiple lineages of colubrid snakes. The fact that these unrelated lineages have evolved venom independently and the fact that Dr. Fry is using an overly broad, medical definition of venom have apparently misled Dr. Fry and his colleagues into concluding that venom evolved in the common ancestor of the Colubroidea. When the proper, biological definition of venom is used, it is clear that venom, which is an adaptive character, has evolved multiple times independently in the Squamata: once in the Helodermatidae, once in the Viperidae, once in the Elapidae, and a few times independently in the large family Colubridae.

Reference

Kardong, Kenneth 2002. COLUBRID SNAKES AND DUVERNOY’S ‘‘VENOM’’ GLANDS. J. TOXICOL.—TOXIN REVIEWS, 21(1&2), 1–19

We've gone down this road before. Anytime you want to write a letter to Toxicon critiqueing the work, I will be more than happy to respond point by point.
-----
Dr. Bryan Grieg Fry
Deputy Director
Australian Venom Research Unit
University of Melbourne

www.venomdoc.com

You are quite correct, Dr. Fry. You could not refute my arguments before and you cannot refute my arguments now. One thing I do like to add.

In order to tackle the question of the origin and evolution of venom (which is what you are purportedly doing), one must first adopt the biological definition of venom, namely biological secretions that are used to kill or subdue prey. Only when one adopts this definition can a biologist go about deciding when and how venom first evolved for this function. Using your medical definition, all that you and your colleague can say is when a molecule with toxic properties may have first appeared in the evolutionary history of snakes.

Why such a molecule first appeared can never be answered by your investigation because you are ignoring the question of function, specifically what function did these toxic molecules perform (and may still perform) when it first evolved. Was it digestion or some other unknown function? You and your colleagues will never know because you are simply guessing that it first evolved to function as a venom.

Okumura et al. (2002) have recently isolated PLA2 from the lung and liver of a nonvenomous snake, Elaphe quadrivirgata. Unlike you and your colleagues, Okumura et al. do not assume that this molecule evolved in the common ancestor of colubrids and viperids, nor do they assume that this molecule is evidence of the early evolution of venom, even though PLA2 is a key component found in the venom of viperids. The more objective approach taken by Okumura et al. will more likely reveal the answer to the question sought by biologists such as Kenneth Kardong. And that question is the original role the toxic molecules had when they first evolved in snakes. By assuming that they originally evolved as venom as you and your colleagues are doing, you will never know the answer to that important evolutionary question.

Regards.

Reference

Kohji Okumura, Seiji Inoue, Kiyoshi Ikeda, and Kyozo Hayashi 2002. Identification of beta-type phospholipase A2 inhibitor in a
nonvenomous snake, Elaphe quadrivirgata. Archives of Biochemistry and Biophysics 408: 124–130

>>You are quite correct, Dr. Fry. You could not refute my arguments before and you cannot refute my arguments now.

Put them in writing to a journal and we'll see how we go shall we?

By the way, what is your name other than President of the Flat Earth Society?

Ciao
B
-----
Dr. Bryan Grieg Fry
Deputy Director
Australian Venom Research Unit
University of Melbourne

www.venomdoc.com

Dr. Fry wrote:

"Put them in writing to a journal and we'll see how we go shall we?"

How much time do you think that process will buy you? If you could indeed refute my arguments, you would have already done so. If you have no response, then more time will not help you.

Nice try sunshine.

A nice demonstration of your complete lack of ability to understand any scientific data is that Okumura et al did not isolate at phospholipase, they isolated an inhibitor of a phospholipase.

Duh.

Yeah, I think now the line has to be drawn between "venomous" and "dangerously venomous", at least for the colubrids.

I personally think the term "Venomous" is overused. Frankly, it is a FLASH WORD (one that causes an immotional rather than logical response...a term used in advertising).

No good can come from it's continued use, as the general(non snake loving) public probably will not be willing to take that step of accepting Venomous as not allways meaning Dangerous.

The question would be what to use instead, to describe the difference between Dangerous and Safe species. Legally it could be a nightmare if and when goverments look at this material and try to enforce existing laws that are not that specific.

It boils down to the same thing. Every bit of knowledge has a price...

Frank
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"The luxury of not getting involved departed with the last lifeboat Skipper..."

I completely agree that there is a remarkable distinction between venomous colubrids (virtually all) and dangerously venomous colubrids (a much smaller number of snakes). The key here is that the dangerous ones do not lump all next to each other but rather are scattered liberally all through the advanced snake tree, with each colubrid family having at least one dangerously venomous species. Legislatively, the vast majority of the colubrids should continue to be treated as 'non-venomous' since from a practical perpective that is what they are. However, a number do need to be considered as truly venomous. Its not an absolute but rather a sliding scale with a somewhat arbitrary cut-off.

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

www.venomdoc.com

Hi,

"What I guess I'm trying to ask is where is the line drawn with an animal whos saliva has destructive properties and what we call a venom?"

>>> Depends who you ask. Check out this previous thread that was posted on the Taxonomy forum. http://forums.kingsnake.com/view.php?id=245507,248601

Personally, I believe Dr. Kenneth Kardong definition of venom vs. toxic saliva makes more sense.
Ignoring published evidence

His concept was based off of his essential unwillingness to accept any 'colubrid' as having venom (even boomslangs or Boigas) and this was based off of a number of assumptions he came up with prior to any biochemical data on the 'colubrid' venoms being available. It came as quite a suprise to even us that the ratsnakes were putting out the classic cobra-style neurotoxins. We certainly didn't expect to find that. This data radically shifts the playing field and allows for evidence based interpretations rather than evidence-free hypotheses.

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

www.venomdoc.com

>>This is sort of in relation to Dr. Fry's article about venomous colubrids. I'm wondering is this similar or related to the documented anti-coagulant properties of the North American Water Snakes (Nerodia sp.)? I've been bitten by these snakes a few times and I can attest first hand to those properties. What I guess I'm trying to ask is where is the line drawn with an animal whos saliva has destructive properties and what we call a venom?

Saliva is just about any buccal secretiont hat accumulates in the mouth. Venom is a specialised secretion produced in specalised glands. The anticoagulants found in Nerodia are secreted by the venom (Duvernoy's gland), so technically, Nerodia are venomous. They are of course also, to all intents and purposes, harmless to humans, as the thousands of popel who have been bitten by them can attest.

Cheers,

Wolfgang
-----
WW Home

"Saliva is just about any buccal secretiont hat accumulates in the mouth. Venom is a specialised secretion produced in specalised glands. The anticoagulants found in Nerodia are secreted by the venom (Duvernoy's gland), so technically, Nerodia are venomous. They are of course also, to all intents and purposes, harmless to humans, as the thousands of popel who have been bitten by them can attest.

Cheers,

Wolfgang"

That definition of venom is quite interesting but not very useful. It is not clear how one is supposed to distinguish a specialized gland from an ordinary gland. The heads of reptiles are filled with glands. For example, in fig. 2 of Kardong (2002) there is a diagram of head glands found in reptiles. These include the posterior, Harderian, nasal, premaxillary, supralabial, palatine, lingual, sublingual, infralabial, mandibular and Duvernoy's glands. Not all reptiles have all of these glands, however. My questions to WW are:

Are all of these glands considered specialized? Do the secretions have to be toxic for them to be considered specialized secretions? Is it true that only toxic secretions from a specialized gland are considered venom? Or are non-toxic substances that are secreted by a specialized gland automatically considered venom even though they may not have toxic properties?

It is quite clear that unless and until these questions have been addressed can we say with any degree of certainty which gland is specialized and therefore which secretions can be considered venom. For now, there is no clear answer to the question of what constitutes venom or a venomous snake in the minds of WW and his colleagues.

Further complicating the issue is the fact that human saliva is toxic if injected subcutaneously. Is human saliva considered venom under WW's definition of venom? Are human beings venomous animals under WW's definition of venomous animals?

Reference

Kardong, Kenneth 2002. COLUBRID SNAKES AND DUVERNOY’S ‘‘VENOM’’ GLANDS. J. TOXICOL.—TOXIN REVIEWS, 21(1&2), 1–19