QUICK WORD ON JOs AGAIN..

["D.W.Naish" <dwn194@soton.ac.uk>]

> As I recall (correct me, please, if I am wrong), Jacobsen's organ is 
> often referred to as an organ of "taste-smell."  

I'm fairly confident that the 'proper' name for them is vomeronasal organs, but
I was so afraid I'd spell it wrong I didn't use it. Of course, my spelling here
is probably wrong too. In any case, the word 'vomeronasal' should help you
imagine the location of the organs in the skull.

> It is located in the 
> roof of the mouth or in the nose (same diff in many tetrapods).  It is what 
> lizards and snakes use to analyze the chemicals picked up on their tongues,
> and I think in mammals it is usually used for analyzing pheromones and the >
> like.

JOs are characteristically (ASAIK) paired in all animals that have them. In
snakes and lizards, many of which have since evolved a bifid tongue, two pockets
open caudally and are directed rostrally. It has been demonstrated recently that
the strongly forked tongue of derived snakes provides them with a kind of
stereoscopic sense of smell, such that they can tell which direction scent
particles are coming from. Surely the bifid tongue has evolved in close parallel
with the JO in lepidosaurs (explaining the fact that the separate forks of the
tongue fit into the separate pouches), while the advantageous stereoscopic
ability was developed too.

> "Flehmen" refers to an animal scrunching up its snout and opening its 
> nostrils to give the pheromones easier access to Jacobsen's organ.

This isn't quite right: the flehman response is a very characteristic action
whereby either the _upper lip_ is raised (e.g. horses) or the gums are pulled
up and the cheek muscles pulled back (e.g. cats) while the mouth is slightly
opened. Nostrils may be flared too, but are not instrumental in employing the
JOs, which are in the roof of the mouth as you now know.

More queries from RR will follow!

Jerry, I can't mail you. Please send me your email domain.. Thanks.

"I always wanted you to go into space man.. intergalactic -???-"

DARREN NAISH