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Old 04-04-04, 10:06 PM   #16 (permalink)
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Quote:
Originally posted by C.m.pyrrhus
As I take it, pit-vipers do "see" and image with their pits. I cannot find a lot of anything, due to lack of books and so on. Yet what I have found relates the pit vipers as able to make an image of what they see from their pits. The way their heat seeking abilities are set up, being heavily modified over the boids, is picked up by the sight processing and is "formatted" into an image in the brain. Testing was done with rattlesnakes, their pits blocked and showed that an average of only 1/3 of the strikes made their targets. With their pits unblocked and eye sight blocked, they had an improved strike percentage.
think about it man, if vipers do make a mental image of prey, its only a blob of heat, think about how heat travels, and its impossible to imagine heat being able to make a picture, even if the heat pits were connected directly to the brain.
sight touches everything, and heat has to travel on to/in/up there heat pits. It probably not much different to feeling somthing warm by ur lip, except much much more sensitive >(
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Old 04-04-04, 11:43 PM   #17 (permalink)
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If we're going to discuss wether snakes "see" heat or not, we pretty much have to define what it means to see. For my money if the heat pits feed into the vision centers of the brain, I could call that seeing. Just because they strike accurately at heat sources doesn't mean they "see". It just means they have accute range and direction fidelity in their heat detection.

The other thing to look into is this: are the heat pits "heat sensors" that can feel heat like our skin can, only more sensitive, or are they infrared detectors. Infrared is electromagnetic radiation (like light) given off by objects based on their temperature. If heat pits are the former, there's no way it can be vision. If it's the latter, you could make the argument that it is seeing.

In any case, the quality of snakes vision certainly varies a lot between species, but I have no idea about color etc...

rg
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Old 04-05-04, 10:37 AM   #18 (permalink)
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Cmp,

I agree with what you've said re: heat pits, striking, etc. I was speaking (in the sense that rg has continued) about what constitutes 'sight'. Semantics, perhaps, but I would say that the term 'sight' is derived from 'eyesight', which implies the use of 'eyes'. Since these heat pits don't replace the eyes, but are in addition to them, I would consider this to be a wholly separate sense, and hence I refer to it as 'heat sensing' for lack of a better, monosyllabic term. Now, one could argue that 'sight' is the perception of light via whatever organs can do it, and since what is being sensed is infrared wavelengths of light, heat pits could be said to 'see'. I just don't use this definition.

"think about it man, if vipers do make a mental image of prey, its only a blob of heat, think about how heat travels, and its impossible to imagine heat being able to make a picture, even if the heat pits were connected directly to the brain.
sight touches everything, and heat has to travel on to/in/up there heat pits. It probably not much different to feeling somthing warm by ur lip, except much much more sensitive "

Now this is absolutely wrong. Heat pits do NOT depend upon radiation or convection to transfer heat from a heat source. They sense the infrared light given off by the object. It is like the thermal imaging cameras you see on TV.

Not sure on the performance of constrictor heat sensors, but viperid sensors are astonishingly accurate and quick. In fact, it was only a few years ago that we could even measure how accurate they are. I'm pulling this from memory, but I believe it was a species of rattlesnake that could determine a difference of 0.003 degrees Celsius, within 0.01 seconds. Now that's pretty sensitive! 'Heat sense' is the main targetting sense for viperids to strike their prey.

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Old 04-05-04, 11:07 AM   #19 (permalink)
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Quote:
Originally posted by Jeff Hathaway


Now this is absolutely wrong. Heat pits do NOT depend upon radiation or convection to transfer heat from a heat source. They sense the infrared light given off by the object. It is like the thermal imaging cameras you see on TV.

this cant be proved.
Ive seen the latest exsperements on tv, were they stick a tupe though the nostrel of a snake, it had nothing to do with infared light
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Old 04-05-04, 01:02 PM   #20 (permalink)
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think about it man, if vipers do make a mental image of prey, its only a blob of heat, think about how heat travels, and its impossible to imagine heat being able to make a picture, even if the heat pits were connected directly to the brain.

The "blob" effect you see on TV shows is relative to the resolution of the device used. The better the device, the better the resolution and the resulting image. Stating that the snake only sees a blob is silly without proof.

The following image was taken with infrared photography:



Assuming that a creature that detects infrared has adapted to visualizing in that mode, the limits at which they can view the world are only defined by the hardware limitations of their own organs.

edit: had to change photo links, as other photo wouldn't load.

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Old 04-05-04, 07:50 PM   #21 (permalink)
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I did a bit of net research after posting last night. I found 2 different sites that said that pit vipers process their heat pit info in the vision centers of the brain. I found no info on python heat pit sensory processing. I also found it pretty much everywhere that the pits detect infrared, and not radiated heat. Makes mucho sense since sensing heat directly would offer almost no range, and pretty poor direction calculation. Just think about convection currents. I dont know if this has been proven, but I can imagine it wouldn't be hard. Isolate receptor cells, and see if infrared stimulates them to fire electro-chemical signals to the nervous system. Even easier...can they sense heat through glass? Glass insulates pretty well against subtle temp fluctuations. If so, it pretty much has to be IR.

I still dont think of it as "seeing". Seems like more of a 6th sense to me.

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Old 04-05-04, 10:27 PM   #22 (permalink)
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I see it as seeing to this degree.

If the whole process is picked up and formatted by the brain exactly like it is for eyesight, then it is in all reality just as eyesight would be. That is what is being shown as a strong possibility in the Crotalinae. I do not see why this cannot be at all possible. It still may be a 6th sense thing as well. But, if properly formatted by the brain, it can be "seen" just as much as what is processed by the eyes. Seeing, in all respects, does not necessarily have to come from eye organs either. It is just that many forms of life has evolved to use these given organs to gain this sense. Yet, there are other methods of sight that the animal kingdom uses. So saying that something does not use eyes to "see" does not make it lacking in sight as we perceive it. We simply use a different organ of choice.

Still, there is a lot of detail and study left in this whole subject of heat sensing in snakes, along with sight. There is an interesting thread on heat pits at the VenomDoc forums if others would like to see more discussion of this subject.
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Old 04-05-04, 10:34 PM   #23 (permalink)
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That line of thought makes a lot of sense, especially with what we're seeing in the development of prosthetic devices.

With profound hearing loss there are new cochlear implants that represent sounds by tone generation. The brain has to learn these patterns, as to a hearing person it would just be so many beeps, but as the brain compensates the person begins to hear the sounds of the world around them in the signal.
Similarly with the CCD based ocular implants in development.

The brain is a complex and mysterious organ. How it interprets sensory data is amazing.
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