Snake noses

["Showalter, Steven K." <SKSHOWA@saix531.energylan.sandia.gov>]

>Steve Showalter says:

>>Snakes do not have "noses" per se, they have nasal openings,

>Although I could be wrong, I'm pretty confident that snakes have
>"real" noses associated with their nostrils.

Well I have been known to be  wrong also (see below:), but I am pretty 
confident that snakes do not have noses in the normal sense of the word. 
 They have air passages that allow them to breathe without having to open 
their mouths (ever seen a snake with a respiratory infection?) , but do not 
have a developed sense of smell associated with an organ that resides there. 
  They do have membranes that are sensitive to high concentrations of 
organics, but the back of your throat is sensitive to high concentrations of 
organics and it doesn't smell or taste them.  I guess it all comes down to 
whether there is a distinct organ there or not.  There should be some 
biologists out there that can answer this one.

>>but the olfactory organ is in their tongue.

>That's not right.

>>It is called a Jacobsen's (sp?) organ,

>Call it by its alternate name, the vomeronasal organ and you won't
>have to worry about how Jacobson (sp?) spelled his name :-).  The organ is
>*not* on the tongue, however.  The organ is in the roof of the mouth.
>Snakes sample the air with their tongues, and then insert the tongue's
>tips into recesses in their palate.  That's were the vomeronasal organ
>resides.

You are correct, I muffed that one, with my major fault being the mixing of 
the properties of the tongue in with the Jacobsyn (sp?) organ.

>I'm slightly more familiar with the struture in mammals than in
>snakes, but I think you're stretching it with "taste, smell and
>temperature".  The vomeronasal organ is specialized for detecting
>non-volatile chemicals, typically proteins.  It's not exactly like
>human smell or taste, so it's probably not fair to refer to it as
>both.  It's just different.  And I'm not sure where the temperature
>sensation bit is coming from... snakes which prey on mammals (and can
>thus rely on temperature cues) typically use heat sensors in pits on
>their faces.

My understanding of the tongue is as an instrument to capture volatile as 
well as nonvolatile materials.   It is a tiny air sampler as well as a 
molecular spatula.    The resulting sample is inserted into the Jacobsin 
(sp?) organ for testing.   If it was only used for nonvolatiles (definition: 
low vapor pressure), why is it used so often in only taking gas samples?  If 
I was looking for nonvolatiles, I would be touching surfaces.  I think what 
you have described above is taste and smell as far as we can tell without 
asking the snake..

The detection of temperature is by the tongue via touch probing, not for 
prey location.  Snakes probe the temperature of surfaces in front of them 
with their tongues to help in thermoregulation when moving from spot to 
spot.

Steve

skshowa@sandia,gov