Besides taste and smell, quite a few vertebrates have a vomeronasal organ - a sense organ usually in the palate. Snakes use theirs for "tasting" molecules their tongues pick up when they flick in and out. Mammals use them mostly for seeing if potential mates are sexually receptive - bulls, for instance, curl up their lip and check out heifers' hindquarters to see if they're in heat.
Humans and the other great apes have a degenerate little VNO that apparently has no sensory nerve connections. The accessory olfactory bulb of the brain, which processes VNO signals in monkeys or bulls, forms in human and ape embryos but disappears before birth. And we and chimps have a bunch of pseudogenes for VNO receptor proteins.
Oh, and the platypus has electrical receptors in its "beak." I've read that they will ignore a rock thrown in their creek, but will immediately go check out a double-A battery.
This message has been edited by Coragyps, 04-26-2005 10:47 PM
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