In the end it appears they can
taste the heat at that low level in order to identify the target spot. The effect was implied and now we have
identified the actual pathways that make it possible.
How vampire bats find blood
By Sharon Oosthoek CBC
News
Posted: Aug 3, 2011
The vampire bat must find a blood meal every one to two days to
survive. A heat-sensing molecule called TRPV1 covering nerve endings on the
bat's nose helps it achieve this goal. (Dr. Pascual Soriano )
How vampire bats know precisely where to bite to strike a
blood-spurting vein close to the skin has always been a mystery — until now.
A team of American and Venezuelan scientists studying wild vampire bats
in South America has discovered a heat-sensing
molecule called TRPV1 covering nerve endings on the bats' noses.
The finding, published in this week's journal Nature, shows
how small changes to a particular species' genes can lead to important
evolutionary adaptations.
In this case, it allows the vampire bat to detect infrared heat and
zero in on the most blood for the bite, says lead researcher David Julius, a
molecular biologist at University of California , San
Francisco
TRPV1 is used by other animals to detect "noxious heat" —
that is, painful heat above 43 C, says Brock Fenton, an expert in the behaviour
and ecology of bats at the University
of Western Ontario
"In vampire bats, however, the TRPV1 activation threshold is
lowered to about 30 C," wrote Fenton in an accompanying commentary piece
inNature.
While scientists have known for a long time that vampire bats' noses
guide them to the best spots, they didn't know how. This new research shows the
key is not just TRPV1, but an evolutionary genetic variation of it that allows
vampire bats to sense low-temperature heat.
Intriguingly, the same molecule is also found on pain sensing nerve
fibres in humans. On our tongues, it allows us to detect the burn of spicy
food. On our skin, it lets us feel the pain of touching a hot object or of a
sunburn.
That's why drug companies are working on developing new pain
medications that target molecules like TRPV1.
TRPV1 belongs to a large family of molecules found in many animals.
Depending on the species, those molecules have slightly different DNA and
appear in different parts of the body.
But what they have in common is that the molecules cover nerve endings
and can alternatively open or close in response to a chemical, heat, cold or
the pressure of touch. With the right balance of openings and closings, the
nerve will fire, sending a signal to the brain that says "hot" or
"cold" or "hard" or "bitter."
Many animals have highly specialized adaptations allowing them to see,
feel, hear or taste in special ways. In humans, painful stimuli signal danger
to the brain and make us pull away to protect ourselves.
"There is a lot of stuff in our environment that we want to stay
away from," said Julius.
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