Dry bites is it a conscious choice or just a lottery?.

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When a drop the size of a couple of sand grains is all that is required, who's to say that residual venom on the fang or in the fang sheath was injected purposefully or just transmitted through touch.
I have heard of envenomation in keepers while cleaning cages where a shed fang has *****ed the finger, but I am unable to verify.
 
When a drop the size of a couple of sand grains is all that is required, who's to say that residual venom on the fang or in the fang sheath was injected purposefully or just transmitted through touch.
I have heard of envenomation in keepers while cleaning cages where a shed fang has *****ed the finger, but I am unable to verify.

Wow, that's pretty interesting.
 
There are three types of muscles in vertebrate animals –

  • Skeletal muscle or "striated voluntary muscle"
  • Smooth muscle or "non-striated involuntary muscle"
  • Cardiac muscle or “striated involuntary muscle"

Only skeletal muscle is under conscious control. Due to the complexities of our nervous system, it is on rare occasions possible for someone with an immense amount of specific training to exercise a measure of conscious over what is normally involuntary muscle. This is the exception to the rule, extremely rare and cannot be achieved by the vast majority who train to do so.

Unfortunately the term “conscious” has a number of meanings which can lead to confusion...

  1. aware of one's own existence, sensations, thoughts, surroundings, etc.
  2. fully aware of or sensitive to something (often followed by of ): conscious of one's own faults; He wasn't conscious of the gossip about his past.
  3. having the mental faculties fully active: He was conscious during the operation.
  4. known to oneself; felt: conscious guilt.
  5. aware of what one is doing: a conscious liar.
Meaning 5 is the correct meaning when discussing physiology and muscles in particular.

The venom glands are not squeezed by the closing of the jaws to cause them to expel venom. Refer to pg 15 “Australian Snakes. A Natural History.” by Richard Shine. Reed Books. The “masseter muscles” attached to the back of the venom glands “contract and squeeze venom from the venom gland through the venom duct to the fang.” To put it simply, envenomation is under the control of the snake.

Studies have found that individuals within the one species can vary in their likelihood to envenomate and so the results are often given as a range e.g. 40% - 50%. It was previously believe that Australian elapids were only likely to envenomate about 10% of the time. More recent research has found this average to be closer to 50% overall.

The amount of venom injected can vary dramatically. From the point of view of the snake, it depends on how long since it used its venom, its state of health, the degree to which the fangs penetrate and where they penetrate, the size of the snake and to what degree the snake is feeling threatened. Obviously clothing has an effect but that is independent of the snake. Those species which chew or deliver multiple bites in quick succession are likely to be more successful in envenomation. The volume of venom that a snake can build up in its venom glands is another factor influencing the success of a snake attempting to envenomate.

I have not covered it all but hopefully that sets the record straight on the misconceptions.

Blue
 
"Only skeletal muscle is under conscious control" yes that's what you'll read in any textbook, but it ain't necessarily so. The lower oesophageal sphincter is smooth muscle yet some people have it under conscious control, which allows them to make a living out of regurgitating light bulbs and stuff. Pretty gross if you ask me....

Oops, just reread your post & see that you made that point, however I still need to point out that skeletal muscles aren't always under conscious control, being part of a reflex arc makes some sense to me, after all I have limited control over my salivation & venom is probably just modified saliva.

Reflex arcs are fast and I reckon eminently suitable for the job.

There's no way to find out though & really does the subjective experience of a snake when it's biting you make any difference?

Also isn't the story of a keeper who got envemomated by a shed tooth / frozen snake just an urban myth?
 
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Only skeletal muscle is under conscious control. Due to the complexities of our nervous system, it is on rare occasions possible for someone with an immense amount of specific training to exercise a measure of conscious over what is normally involuntary muscle. This is the exception to the rule, extremely rare and cannot be achieved by the vast majority who train to do so.
Mikey, I am not sure whether you are meaning to reiterate for emphasis or adding due to perceived omission???

Blue


 
It actually has two primary purposes. It's used to not only immobilise but to assist in the digestion of prey. It's basically a modification of saliva that's found in other vertebrae.

Humans and other mammals have the ability to chew their food where (as we all know) snake don't chew but swallow their prey whole.

Remember when, as a kid we are told to chew our food. Well it's not only to break it into small pieces that can be easily swallowed as a lot of people think. The chewing action creates saliva that when mixed with the food item helps to assist digestion in the gut. The more we chew our food the more saliva mixes with it and the better it digests.

Snake venom contains (as well as many other things) strong enzymes that are very important to assist in the breakdown and digestion of their prey.

Recent research has discovered that pythons have an ancient venom delivery system (not venom glands as such but a system similar to monitors where the venom is stored in small grooves in the jaws and excretes in a form of a saliva) that although not lethal, contains similar enzymes to assist in the digestion of prey (that's why python bites sting and can sometimes become infected). It's presumed that "non venomous" colubrids also have a similar system for the same purpose but it will need further research to confirm.

George.

I was under the impression that venom serving to aid digestion had been disproved or at least while it may in its nature aid digestion in is merely coincidental and not necessary. The apparent health of Raymond Hosers venomoids would seem to verify this.
 
I was under the impression that venom serving to aid digestion had been disproved or at least while it may in its nature aid digestion in is merely coincidental and not necessary. The apparent health of Raymond Hosers venomoids would seem to verify this.
Some venom aids digestion & some doesn't. You can tell by looking at the bite sites - some snakes give horrendous local reaction with digestion of tissue, whereas others just kill you (unless of course appropriate first aid is applied)

Bluetongue1 I'm not reiterating for emphasis, I'm just too lazy to read complete posts before responding. I'll reform my slovenly ways one day...
 
The fact the tissue around some bites may break down is not proof that its design is to aid digestion.
 
The fact the tissue around some bites may break down is not proof that its design is to aid digestion.
The fact that his venomoids are alive does not disprove it either. It merely means they are getting adequate nutrition. This could be because they have an increased diet. The fact that venom breaks down flesh does indeed prove that it aids digestion. That is what digestion is.
 
The fact the tissue around some bites may break down is not proof that its design is to aid digestion.

Design? If you're suggesting that there's a designer there's no need to look for physical evidence, just consult the religious text of your choice,

Otherwise, the fact that some venom digests tissue at the bite site suggests that it has a role in digestion. I don't know how this could be any clearer.
 
Hi Blue.

In reference to my post about venomous snakes closing the jaw to squeeze the venom out of the venom gland, it was merely an attempt to keep the explanation in as simple terms as possible so that the average punter has a chance to interpret the information provided.

It is true that your reference to page 15 of Rick's book explains that the masseter muscle attached to the rear of the venom gland contracts to squeeze the gland and force the venom through the deliver system but it does not explain the mechanics of how the masseter muscles operate. The same explanation in duplicated on pages 304 and 305 of "Herpetology: An Introductory Biology of Reptiles and Amphibians" Laurie J Vitt & Janalee P Caldwell.

This muscle is only a thin membrane located underneath the venom gland. Does it work independently and is it able to be individually controlled by the snake? What mechanics actually cause the muscle to contract? Feel free to correct me if I'm wrong but I believe it just may be attached to other muscles that are connected with both the upper and lower jaws.

Vitt and Caldwell state that venomous snakes can also regulate the amount of venom delivered in a bite by contracting the adductor superficial muscle (connected at the rear of the venom gland) however; again there is no explanation of how the mechanics of an elapid snake bite works.

Kenneth V Kardong's paper "Lateral Jaw and Throat Muscles of the Cottonmouth Snake" explains that along with the masseter muscles the adductor superficial muscles found in elpaid snakes are also instrumental in squeezing the rear of the venom gland to distribute it along the delivery system. These muscles are located at the junction on each side of the upper and lower jaw, and further explains that lateral jaw movement is controlled by the lower jaw. He states that the contraction of the "Modelius compressor grandulae muscle is implemented in venom ejection due to its close association with the venom gland but may likewise be partnered with other muscles in jaw closure".

To me this further suggest that it is highly likely the amount of pressure applied by the lower jaw at the time of a bite has a direct effect on the amount of venom delivered in a bite.

Now in saying all this and considering that elapids tend to either bite their intended victim/prey in a deliberate hard biting action and/or maintain a grip on same to inject sufficient quantities of venom to immobilize their prey it is more than likely a that a choice has been made by the snake to bite hard in such a situation and thus apply sufficient pressure on all the muscles mentioned to deliver the quantity of venom determined to immobilize and subsequently kill the item being bitten.

To me. whether this is a conscious choice to choose the amount of venom delivered or simply an act of instinct appears to be open to debate.

I don't know about you but I have personally experienced both wet and dry bites from small Australian elapids as well as a dry bite from a Death Adder and full envenomation form a Red-bellied Black, Tiger Snake and Brown Snake. I can assure you that on each occasion when I have been envenomed I felt a notable difference in the amount of pressure applied by the snake's upper and lower jaws when it is a deliberate and intentional bite compared to when I have suffered a dry bites which (at least in my case) have always occurred where the snake has failed obtain contact with its bottom jaw.

So it would appear to me that it is a reasonable assumption that to add to all the other possibilities that may contribute to a dry bite, it may be possible that what I have outlined may just be another contributing factor to the discussion.

I reiterate that based on personal experience and from what I have read this is just my personal assumption of how a dry bite may occur.

George
 
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Hi Blue.

In reference to my post about venomous snakes closing the jaw to squeeze the venom out of the venom gland, it was merely an attempt to keep the explanation in as simple terms as possible so that the average punter has a chance to interpret the information provided.

It is true that your reference to page 15 of Rick's book explains that the masseter muscle attached to the rear of the venom gland contracts to squeeze the gland and force the venom through the deliver system but it does not explain the mechanics of how the masseter muscles operate. The same explanation in duplicated on pages 304 and 305 of "Herpetology: An Introductory Biology of Reptiles and Amphibians" Laurie J Vitt & Janalee P Caldwell.

This muscle is only a thin membrane located underneath the venom gland. Does it work independently and is it able to be individually controlled by the snake? What mechanics actually cause the muscle to contract? Feel free to correct me if I'm wrong but I believe it just may be attached to other muscles that are connected with both the upper and lower jaws.

Vitt and Caldwell state that venomous snakes can also regulate the amount of venom delivered in a bite by contracting the adductor superficial muscle (connected at the rear of the venom gland) however; again there is no explanation of how the mechanics of an elapid snake bite works.

Kenneth V Kardong's paper "Lateral Jaw and Throat Muscles of the Cottonmouth Snake" explains that along with the masseter muscles the adductor superficial muscles found in elpaid snakes are also instrumental in squeezing the rear of the venom gland to distribute it along the delivery system. These muscles are located at the junction on each side of the upper and lower jaw, and further explains that lateral jaw movement is controlled by the lower jaw. He states that the contraction of the "Modelius compressor grandulae muscle is implemented in venom ejection due to its close association with the venom gland but may likewise be partnered with other muscles in jaw closure".

To me this further suggest that it is highly likely the amount of pressure applied by the lower jaw at the time of a bite has a direct effect on the amount of venom delivered in a bite.

Now in saying all this and considering that elapids tend to either bite their intended victim/prey in a deliberate hard biting action and/or maintain a grip on same to inject sufficient quantities of venom to immobilize their prey it is more than likely a that a choice has been made by the snake to bite hard in such a situation and thus apply sufficient pressure on all the muscles mentioned to deliver the quantity of venom determined to immobilize and subsequently kill the item being bitten.

To me. whether this is a conscious choice to choose the amount of venom delivered or simply an act of instinct appears to be open to debate.

I don't know about you but I have personally experienced both wet and dry bites from small Australian elapids as well as a dry bite from a Death Adder and full envenomation form a Red-bellied Black, Tiger Snake and Brown Snake. I can assure you that on each occasion when I have been envenomed I felt a notable difference in the amount of pressure applied by the snake's upper and lower jaws when it is a deliberate and intentional bite compared to when I have suffered a dry bites which (at least in my case) have always occurred where the snake has failed obtain contact with its bottom jaw.

So it would appear to me that it is a reasonable assumption that to add to all the other possibilities that may contribute to a dry bite, it may be possible that what I have outlined may just be another contributing factor to the discussion.

I reiterate that based on personal experience and from what I have read this is just my personal assumption of how a dry bite may occur.

George
Very interesting and informative post George. It sounds like the actual muscle flex isn't voluntary but actually driven by the amount of pressure delivered but this is actually in debate as to whether the pressure is deliberate or an instinct. I can see with the limited brain function of snakes bites being instinctual and the primal drive of the snake biting prey could overcome the snakes thoughts causing it to bite hard but also wonder if they are more intelligent than we give them credit for and they can actually differentiate between defensive bites and bites to kill.
 
If venom delivery is not voluntary in any way...how do we explain the spitting species?

D
 
I was under the impression that venom serving to aid digestion had been disproved OR AT LEAST WHILE IT MAY IN ITS NATURE AID DIGESTION IN IS MERELY COINCIDENTAL AND NOT NECESSARY The apparent health of Raymond Hosers venomoids would seem to verify this.

The fact the tissue around some bites may break down is not proof that its design is to aid digestion.

The fact that his venomoids are alive does not disprove it either. It merely means they are getting adequate nutrition. This could be because they have an increased diet. The fact that venom breaks down flesh does indeed prove that it aids digestion. That is what digestion is.

I would say it does disprove it, if the venom was necessary for digestion then surely you would have to expect complications of some form in the animals health if the venom were removed. as capitalised in my above post I recognise that it aids digestion I'm just saying it isn't necessary and/or its evolutionary function as GBWhite suggests


Design? If you're suggesting that there's a designer there's no need to look for physical evidence, just consult the religious text of your choice,



Otherwise, the fact that some venom digests tissue at the bite site suggests that it has a role in digestion. I don't know how this could be any clearer.
By design I mean its evolutionary purpose or "evolutionary design" whether you like my choice of words or not I think you knew what I meant.

That has always been clear. Again Im just saying that that particular role is unnecessary and not a Primary function as GBwhite suggests.
If it were a Primary function then why do venomoids function without it?
 
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I would say it does disprove it, if the venom was necessary for digestion then surely you would have to expect complications of some form in the animals health if the venom were removed. as capitalised in my above post I recognise that it aids digestion I'm just saying it isn't necessary and/or its evolutionary function as GBWhite suggests



By design I mean its evolutionary purpose or "evolutionary design" whether you like my choice of words or not I think you knew what I meant.

That has always been clear. Again Im just saying that that particular role is unnecessary and not a Primary function as GBwhite suggests.
If it were a Primary function then why do venomoids function without it?

Only a study feeding captive venomoids the average diet of their wild counterparts would prove the theory, I personally think its just as plausible to say that producing healthy captive specimens without the benefit of venom aided digestion could be attributed to the added nutrition of a stable dietary intake.

That being said my personal belief is that primary role of venom in at least most Australian species is to immobilize prey and that if venom was needed fro digestion then why have so many reptiles evolved without it?
 
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It amazes me how some people read posts.

First off I don't recall stating that venom is necessary or needed for the digestion of prey.

I agree that it may not be necessary because snakes already have strong natural digestive secretions. If the post is read correctly it states that a primary function of venom assists with digestion of prey. It appears to assist by increasing the time taken for food to digest.

Thomas & Pough (1979) found that injecting mice with Western Diamondback Rattlesnake (Crotalus atrox) venom before being fed to non-venomous snakes increased the rate of digestion. They found that the venom's proteolytic activity loosened hair and weakened the internal organs of prey resulting in the more rapid rupturing of the visceral cavity. This provided the natural digestive secretions of the snakes stomach a larger surface area to act on resulting in the faster digestion of prey.

Nicholson & colleagues (2006) found that the Australian Coastal Taipan (Oxyuranus scutellatus) venom increased the rate that soluble proteins were released and although the mechanism was not studied, suggested phospholiphase may play a role by disrupting cell membranes.

Nicholson, Mirtschin, Madaras, Venning & Kokkin (2006) revealed analysis of Australian Coastal Taipan venom increased the rate that proteins were released suggesting the potential importance of envenomation in the digestion of whole prey.

Reichert (1936) found that envenomated prey ingested by the Brazilian Jararacussu (Bothrops jararacussu) was digested over 4 to 5 days whereas where non-envenomated prey was ingested the process took between 12 to 14 days.

Zeller (1948 found similar results in Asp Viper (Vipera aspis) where envemonated prey took 3 days to digest whereas non-envenomated prey took between 5 & 8 days.

Cheers,

George.
 
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If venom delivery is not voluntary in any way...how do we explain the spitting species?

D

Very good point
Even with various spitting cobra species there is a huge range of difference in both accuracy and amount of venom used
Javans are deadly accurate even when only a few months old
Baby Javans are cool to watch... They peel their lip back but nothing happens
Equatorials are much less accurate and appear to dribble a lot more out
 
My apologies for misreading your post George and then exacerbating the conversation further with my own difficulty at explaining myself in writing.
Unfortunately the nature of forums means members are from varying levels of experience, understanding of reptiles and ability with written English. Rather than being argumentative I was just hoping to stimulate conversation and information sharing on a subject I like. Unfortunately due to misinterpretation and/or Mikey-Mikes condescending I'm right your wrong attitude i felt the need to defend my opinion and understanding of the subject

I took your use of the word "primary" (first in line of importance) as meaning necessary.

Maybe in the wild the increased speed of digestion is a necessary function in order to decrease the time spent vulnerable to predation, whereas captive venomoids don't have this to contend with and therefore function quite well without it.

Thanks for taking the time to reference some studies.

Cats change colour to suit there environment?
 
All cats are grey in the dark refers to the evidence one see with ones own eyes and accepts as fact, Thus without light to see them properly they are grey but if you look at the subject properly you find evidence otherwise. Basically, what you see is not always the truth.
 
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