Varanus bengalensis - Kills a human

[murrindindi]

Originally Posted by nepoez

Do tegus have venom too?

Hi, no, Tegus don`t have venom, they are closely related to the Lacertid lizards (which don`t have venom either), the fact they bear some resemblance to Varanids in appearance is just convergent evolution.

[MDT]

Originally Posted by nepoez

Do tegus have venom too?

Laser beams....big ones too.

[bodiddleyitis]

I think what the science has shown is that monitor lizards, along with many other lizard families, produce molecules of venom. Up to now, despite the hysteria and hype, there hasn't been any evidence that they are venomous in a clinical sense: the medical world does not recognise Varanus envenomation. When people hear that local lizards are venomous they will kill them to prevent them from doing any harm. They won't find the Nature article that describes how extremely low concentrations of venom molecules can be detected using clever techniques. Some individuals react mildly to monitor lizard bites, but nobody has previously proposed that the "venom" can be fatal. The huge problem with this paper is that there is no lizard and no bite wounds. If you were asked to guess what had killed this unfortunate lady you'd have to presume it was a viper. There's no proof except hearsay that venom from a monitor lizard bite has killed her. Consider the huge number of lizard keepers and field herpers who have sustained much more serious bites. Why haven't any of them come anywhere close to death? I'm very sceptical about the notion of clinically venomous monitor lizards, and if this is the best proof that it happens I'll wait for better documented cases before I start warning people that the lizards they currently tolerate are potentially fatal.

[formica]

Originally Posted by bodiddleyitis

I think what the science has shown is that monitor lizards, along with many other lizard families, produce molecules of venom. Up to now, despite the hysteria and hype, there hasn't been any evidence that they are venomous in a clinical sense: the medical world does not recognise Varanus envenomation. When people hear that local lizards are venomous they will kill them to prevent them from doing any harm. They won't find the Nature article that describes how extremely low concentrations of venom molecules can be detected using clever techniques. Some individuals react mildly to monitor lizard bites, but nobody has previously proposed that the "venom" can be fatal. The huge problem with this paper is that there is no lizard and no bite wounds. If you were asked to guess what had killed this unfortunate lady you'd have to presume it was a viper. There's no proof except hearsay that venom from a monitor lizard bite has killed her. Consider the huge number of lizard keepers and field herpers who have sustained much more serious bites. Why haven't any of them come anywhere close to death? I'm very sceptical about the notion of clinically venomous monitor lizards, and if this is the best proof that it happens I'll wait for better documented cases before I start warning people that the lizards they currently tolerate are potentially fatal.

venom has been proven conclusively in varanids...check thru this forum, there are various links to papers on the topic (you'll have to wade thru lots of arguing on the subject tho lol)

[murrindindi]

Originally Posted by formica

venom has been proven conclusively in varanids...check thru this forum, there are various links to papers on the topic (you'll have to wade thru lots of arguing on the subject tho lol)

.
I remember you dismissing Bryan Grieg Fry`s findings when you claimed the Komodo dragon`s venom wasn't efficient because it didn`t kill the largest prey quickly (it was never claimed it was the primary weapon), that doesn`t mean it`s not an efficient addition to their arsenal!?
As far as I know, Bryan has never claimed the venom itself it was of any real danger to "humans".

[formica]

Originally Posted by murrindindi

.
I remember you dismissing Bryan Grieg Fry`s findings when you claimed the Komodo dragon`s venom wasn't efficient because it didn`t kill the largest prey quickly (it was never claimed it was the primary weapon), that doesn`t mean it`s not an efficient addition to their arsenal!?
As far as I know, Bryan has never claimed the venom itself it was of any real danger to "humans".

then you clearly didnt read what I wrote very well, because that is not what I said at all!

I disputed that the Venom was part of the most efficient delivery systems in reptiles, and I disputed that it was one of the most efficient venoms known, which is what was being asserted by some...and then didnt Dr Fry came along and agree with me, the delivery system is not the most efficient by a long shot, and the length of time it takes to work also puts it as relatively inefficient in comparison to most of the well known venomous reptiles.

edit: infact, checking back, the word was ''advanced'', not ''efficient'' - makes no difference to my point however.

I recon if you weren't so quick to jump on my every word with uncalled for disdain and ridicule, you might read what I write a bit better and we'd probably have much more interesting conversations.

[murrindindi]

Here you are, Formica....




: Recent Komodo postings of Dr. Bryan Fry

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Quote:
Originally Posted by murrindindi View Post
Quote:
Originally Posted by formica View Post
l - and the fact that animals do not die within minutes of being bitten by a Komodo, indiciates that their Venom is not effeciant, or even massivly useful


{murrindindi): [QUOTE]:
Yes, you did clearly state it wasn`t efficient and not "massively useful" (important)!


(Formica): [QUOTE]:
I stand by my assertion that its not effeciant, and because of the time scales involved I dont see how it can be massivly useful - whether its important or not, I dont know, do we even know what the venom is doing?

Do we know for sure, that the animals which are coming to the pools, are not already dying? its just very strange, for an animal to accept being bitten by a predetor, and then just sits there to die for days on end - do we know how many animals that are bitten, then die and are eaten by the Komodo? or the number of animals which attempt to flee or fight back, if they dont, then why not? could this be a special property of the venom or is something else going on? there are too many unanswered questions for this riddle to be solved yet imo

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[murrindindi]

Perhaps if you didn`t describe a difference of opinion as an "attack" we might indeed have much more meaningful discussions!

[formica]

My Overall point, outlined in full

Originally Posted by formica

indeed, advanced does not mean complex, advanced indicates some improvement in the efficiency of the venom delivery

I'm not sure that the Komodos method is more effeciant, than injecting direct into the blood stream tbh, the komodo is pretty much relying on an unknown amount being smeared over the skin and inner tissues, the body of the animal will quickly react and cause swelling which will slow down the amount of venom that can enter the body, injection doesnt give the body this oppertuntiy, the venom will spread thru the body within seconds, depending on the heart rate of the animal - and the fact that animals do not die within minutes of being bitten by a Komodo, indiciates that their Venom is not effeciant, or even massivly useful

Dr Fry's version, making the point about the mechanical action of the bite, and the fact that the venom prevents coagulation, but the venom does not directly cause death

and highlighted at the bottom relating to the delivery mechanism

and time till death

Originally Posted by venomdoc

The anguimorphs have a combined arsenal system employing teeth and venom. Helodermatids are one extreme, with the deeply grooved gracile teeth restricted to a venom delivering role. In contrast, komodos have the large serrated teeth as the primary weapon, using a grip-and-rip strategy to inflict deep parallel wounds. Mechanical damage that in some cases results in very rapid death from blood loss (eg slicing the femoral artery). The role of the venom is to exaggerate the blood loss and shock inducing mechanical damage caused by the bite. We have identified two main actions common to all anguimorph venoms: anticoagulation and hypotension. Enough loss of blood would lead to a drop in blood pressure sufficient to induce shock or unconsciousness. So anticoagulant toxins facilitate a steady march in this direction. Similarly,hypotensive toxins accelerate the unconscious endpoint.

Komodos evolved not in Indonesia but in Australia, and were not the biggest to have roamed, at least two larger varanids existed to predate on megafauna. The second largest radiated to Timor while komodo radiated to Flores and nearby islands. The modern day situation is that the komodos have three mammalian potential prey choices. All of which are feral. The introduced pigs and deer are within the natural prey size (40-50 kg) while the buffalo are dramatically larger than would have been a reasonable size for komodos to kill and also occupy an ecology unlike anything in Australia.

These collective differences are starkly reflected in attack success. Attacks on pigs and deer are extremely successful. About three quarters bleed out within the first thirty minutes and another approximately fifteen percent succumb within three or four hours. Repeated attacks by the same or other komodos is not uncommon. In dramatic contrast is the outcome of attacks on water buffalo. Which invariably get away, with deep wounds to the legs. Upon which they go and stand in feces filled watering holes. Creating a perfect scenario for dramatic infections. Not from the dragons mouth, but rather having an environmental source. Deep wounds in feces laden water is a perfect scenario for the flourishing of bacteria, particularly the nasty anaerobic types. Thus, the sampling of komodo mouths that purported to show them harbouring pathogenic bacteria neglected to sample the real source of any infection to the water buffalo: the faeces filled waiting hole the dragons recently drank from. It has been a man made artificial scenario all along that has nothing to do with the evolution of the predatory ecology of komodos.

Having gotten septicaemia in Flores from deep lacerations resulting from a boating mishap in Flores harbour (water that is pretty disgusting) I can attest to how quickly such environmental sources can produce life threatening infections. As a consequence of the Flores doctor doing a shockingly inept job of cleaning up the wounds before stitching them up, I ended up delerious and near unconscious in the Bali International SOS clinic 36 hours getting emergency IV antibiotics.

There is nothing special about komodos. They are simply the largest extant species of a clade that had two extinct larger species and has two extant species (V. varius and V. salvadorii), all of which share the unique large,blade like serrated teeth. None of which have ever had the slightest whiff of using bacteria as a weapon.

As for the relative complexity of the varanid venoms glands, this was from our 2009 paper when we discovered it had six discrete compartments. More than any other reptile. However, when in 2010 we looked at a variety of anguimorpha lizards, varanid and non-varanid, we discovered that the ancestral condition was to have one gland per tooth, so 15 or more small glands for anguiids for example, with these glands fusing into larger structures independently in lanthanotids/varanids and also in the helodermatids. So the lanthanotid/varanid gland structure comprised of a encapsulated gland with fused compartments (6 total including one massive one as per the images on my webpage www.venomdoc.com) is equally derived to the helodermatid. However, the most advanced venom delivery architecture in the reptiles is of course the three independent lineages of front fanged snakes (Atractaspis, plus elapids and vipers), with the vipers the most intricate due to the hinged fangs.

Cheers
Bryan

I was not disputing the venom's existence, only its efficiency and how advanced it was compared to other venomous creatures. as Dr Fry clearly states, it is slow, taking 30 minutes to act, it does not act by itself by potentiates the effects of the bite itself, and its delivery mechanism is crude in comparison to many other venomous reptiles.

[MDT]

Originally Posted by formica

Dr Fry's version, making the point about the mechanical action of the bite, and the fact that the venom prevents coagulation, but the venom does not directly cause death

But for the lack of bite and envenomation, the prey would not be in danger of an early demise.

Bite---->Wound----->Envenomation------>Coagulopathy----->Bleed to death--->

----->Toes up.

It really doesn't matter if it takes 5 minutes or 5 hours. The end result is dinner.

[Mikoh4792]

Originally Posted by MDT

But for the lack of bite and envenomation, the prey would not be in danger of an early demise.

Bite---->Wound----->Envenomation------>Coagulopathy----->Bleed to death--->

----->Toes up.

It really doesn't matter if it takes 5 minutes or 5 hours. The end result is dinner.

Yup it's whatever works for the envenomator.

[formica]

In terms of the prey dying, yes, the end result is the same, but in terms of the predator getting its meal, that is not necessarily the case, the longer it takes for the animal to be immobilized, the more chance there is that the predator will miss out on a meal as the prey tries to escape and moves out of range, regardless of whether it survives the attack or not.

that is what I mean by efficiency, compared to for eg a Rattlesnake striking a rat, or a Red Back striking a fly, both those instances cause very rapid immobilization of the prey, thus reducing the risk that the prey will be able to run out of range, and reducing the risk of injury to the predator as the prey fights for its life

killing the prey is useless, if the predator cannot eat it, its a waste of energy and venom.

Clearly the venom is efficient enough for monitors that use it, but the discussion was leaning towards the idea that it was the most advanced/efficient venom and delivery mechanism in the reptile world, which it clearly isnt.

[Mikoh4792]

Well this is my limited understanding of how these animals eat(from animal planet shows I've watched as a kid.....lol). If they are going to eat a big prey animal, don't they give it a good bite, let it run off a good distance so that they can follow the scent trail and find it later when the prey is already dead? Isn't this in a way effective?

[formica]

Originally Posted by Mikoh4792

Well this is my limited understanding of how these animals eat(from animal planet shows I've watched as a kid.....lol). If they are going to eat a big prey animal, don't they give it a good bite, let it run off a good distance so that they can follow the scent trail and find it later when the prey is already dead? Isn't this in a way effective?

Yes, and thats fine as long as they can find it afterwards, before another predator or scavenger comes along, and as long as the predator is not injured in the process. Prey pumped up on adrenaline can run a long way in 30 minutes to 5 hours, and can do allot of damage to any predator that doesnt avoid it or isnt able to physically restrain it

the issue is not ''does it work'', the issue is people saying that it is more advanced and more efficient, than for eg a hinge fanged pit viper, or a spitting cobra, both delivery systems are far more advanced, hinged fangs physiologically, and spitting with its significant brain power used to aim the jet - and compared to venoms which take a few minutes to act, 30 minutes is a long long time

[Lankyrob]

From memory the komodo is the apex predator on their islands so they dont really have the risk of other animals stealing their kill, being reptile rather than mammal they dont have to worry how ong it is is between meals. And by being out of the way while the animal diess then they are at little risk of being injured by an animal in its death throes.

To my mind if the lizards were losing a number meals due to the "inefficient" way their prey dies then evolution would have kicked in and made either the delivery or the venom itself more effective.