Hognose bite!

[bud mierkey]

ha ha

So should we call hognoses toxic snakes?
are you still holding to your opinion that its allergic reaction
that causes the massive swelling?

 

[Seamus Haley]

So should we call hognoses toxic snakes?

Or... snakes that produce toxins. We shouldn't call them venomous though. While the toxin production is very similar, it lacks the important aspect of a delivery system.

are you still holding to your opinion that its allergic reaction that causes the massive swelling?

Kinda... allergic reaction isn't exactly the right way to describe it. Individual sensitivities to the toxins would be a bit more like it. The exact toxin composition will vary depending on what the hognose last ate, how old it is, what the temperature is and many other factors. The type of tissue that the toxin ends up in will have different reactions too... And then there's a great deal of truth to the statement that not everyone reacts the same anyway, even if all other factors were equal. I've been chewed on by hognoses, it kinda tingled a bit. Other people get chewed up and end up looking as if they were tagged by something that's truly venomous.

Out of curiosity, ever seen what happens to a toad or lizard that gets bitten and escapes?

Very interesting, if not pretty... the toxins in snakes are generally geared towards their common prey items, having stringer effects on the types of organisms that they're most likely to eat. This goes for toxic species, like hognoses, nerodia and garters and true venomous species. A very string reaction to hognose saliva isn't a common one in people, it happens obviously but it's not very likely in most individuals.

 

[bud mierkey]

ok

When it warms up I will test a toad with the saliva it sounds neat.
later

 

[bud mierkey]

bryans input

seamus,
here is bryans input on the subject

>Bottom line though... heterodon don't have a delivery system for their toxins, this is essentially the defining point of the term "venomous" and the manner in which it is applied is the point which makes venom unique from other toxins.

Actually, Heterodon have quite well developed rear teeth and use them to deliver the venom to their prey items (prey capture of course being the original function of venom) and have even caused obvious human envenomations (but very unlikely to be lethal but that is different from being venomous).

Venom predated fangs rather than the other way around and evolution does only one thing at a time (ie fangs and venom did not evolve simutaneously). Venom predating fangs is a perfectly logical scenario since there cannot be a strong selection pressure for the evolution of fangs in the absense of a potent venom worth delivering. Venom is delivered in the non-front fanged species even in the absense of greatly enlarged teeth, the normal teeth are quite capable of breaking the skin of a frog and delivering enough venom to aid in prey capture.

We have shown in other papers in press that in some cases, even with the species that lack greatly enlarged teeth, the venom is just as toxic as comparable elapid venoms. There is a tremendous range of toxicity, development of teeth, venom yield, etc. Exactly what would be expected considering venom has been around for over 60 million years and that the basal venomous snake has diversified into about eight different families, with highly advanced fangs evolving independently on at least four different occasions.

Cheers
Bryan

_________________
Dr. Bryan Grieg Fry
Australian Venom Research Unit

 

[Seamus Haley]

As much as I dislike finding myself on the opposite end of a debate with someone as credible as Dr Fry, I'm going to continue to disagree, even if it's simply a matter of semantics.

Venom predated fangs rather than the other way around and evolution does only one thing at a time (ie fangs and venom did not evolve simutaneously).

Evolution does a multitude of things simultaneously, organisms do not adapt in only a single facet of their biology, but constantly and continuously in EVERY aspect to an ever changing environment.

The definition of "venom" is a toxin which is injected, has an injection method. So while the toxin can develop in ever increasing potentcy, it is not a VENOM in the strictest sense of the word until the injection method is present.

The rear fangs have been strongly evidenced to be present for reasons other than toxin injection, the ducts which carry the toxins into the mouth don't open very close to the rear teeth and those rear teeth are not hollow, not grooved and pressure exerted on them does not cause a signifigant increase in the amount of toxins present in the saliva.

Dr Fry has been pushing his evolutionary theory, one which must be noted to contradict all those which had gone before it, not to say it's not accurate, just that, being new, it's not as well evidenced. Because of the manner in which he has been looking at the evolution of venom, he has reversed the definition of "venom" as well. Rather than "Colubrids are evolving towards venom" he is working on "Colubrids are evolving away from venom" and as such it is important that others accept his definition of venom as simply being a toxin. As of yet... and again, not to detract from his credibility or intend any disrespect, he has not shown any of the environmental factors which would be responsible for the loss of an evolutionary edge, the loss of an advantage over other species and other individuals within a population. It's an important question that will have to be answered before his theories are really accepted by "the masses", in some instances I'll accept the word of an obvious expert within their own field... But for something so radically different than what was previously thought to be true, I'd suggest additional evidence. The prescence of similar toxins is important, but until it's shown otherwise, I'm still going to work off the idea that it happened the other way around.