The vampire bat, Desmodus rotundus, must find a blood meal every one to two… (Dr. Pascual Soriano )
Vampire bats like it warm: To home in and bite with fanged efficiency, they've developed a temperature sensor to guide them to their prey, a new study has found.
All mammals need heat sensors to help them avoid potentially harmful temperatures such as those that would be encountered from a forest fire or dangerously hot water. This is achieved by a protein called TRPV1 that forms a pore — known as an ion channel — in the membranes of cells.
TRPV1 detects temperatures higher than 109 degrees Fahrenheit. But vampire bats, thanks to evolution, have an additional, modified form of the channel that is sensitive to lower temperatures, around 86 degrees.
"It's like a thermostat," said David Julius, a molecular biologist at UC San Francisco and the lead author of the study, which was published online Wednesday in the journal Nature.
The modified channel, dubbed TRPV1-S, is found only in nerves in the face and special organs near the mouth and nose that the bat uses to precisely detect infrared radiation. That allows it to find a good, warm spot on its prey, where there are likely to be blood vessels, when it gets up close.
"There's never been a paper explaining how vampire bats detect infrared radiation," said M. Brock Fenton, a bat ecologist at the University of Western Ontario in Canada, who was not involved in the study.
Among vertebrates, only vampire bats and three types of snakes have this sense. Bats that feed on fruits, nectar or insects do not have TRPV1-S, suggesting that the special channel evolved to meet vampire bats' bloody diet.
TRPV1-S is shorter than the standard channel: Vampire bats make the modified form through a molecular trick called splicing. All of their cells have the same copy of the TRPV1 gene, but in the facial nerves, they edit out a chunk of the protein-making instructions to make the shorter TRPV1-S.
The researchers also found that some of the genetic instructions that make the splicing possible in vampire bats are also present in the DNA of cows, dolphins, horses and dogs, though these creatures do not make TRPV1-S. This says interesting things about bat evolution, the scientists wrote.
Bats were generally believed to be the cousins of rats and mice based on similarities in their body structures. But more recent studies of their genes suggest that they are more related to cows and horses — and the new findings support that idea.