Vampire bats feed on warm blooded animals, using heat sensors in the nose to locate blood flow. An alteration of the TRPV1 protein in the sensory neurons of vampire bats has been discovered as the mechanism behind their ability to sense heat.
by Alison Kochersberger
Emerging at night to feed, the vampire bat diet consists exclusively of the blood of sleeping animals. They will not remove enough blood to cause harm to the host. The habitat of vampire bats spans from Mexico to South America. Although it is not common, they have been known to feed on humans. The vampire bat lands close to and crawls towards its prey, using its heat-sensing ability to locate where blood is flowing on the host. This heat sensor is located in the nose of the bat. The shape of the vampire bat’s nose differs from the fruit bat, which does not feed on blood. It is the three ‘leaf pits’ on the nose of the vampire bat that give it the ability to locate blood flow on its victim in the form of infrared (heat) stimuli.
When investigating the function behind the ability to detect heat within these ‘leaf pits’, researchers found that the sensory nerves were larger, as they are in snakes that can detect infrared. Other types of nerves were observed to have the same structure as in bats that cannot detect heat. Because of this observation, researchers wanted to find if there was a genetic difference in these sensory nerves from the nerves that serve other functions.
They compared the genetic sequences for the sensory nerves and normal nerves. The researchers found that there was an alteration in TRPV1, a capsaicin receptor, a protein, that is activated by temperature. Capsaicin receptors also produce a burning sensation when consuming hot chili peppers. The alteration was due to a segment of the receptor being removed in a process called splicing, resulting in a shorter protein. It was found that the shorter protein had increased heat sensitivity, activating at a temperature 10°C lower than the long version of the receptor.
Next the researchers looked to see if this alteration occurred in other species. They found that other bats and moles could all undergo a similar modification of shortening this receptor. Cows, pigs and dogs could also experience a modification, but it would produce an extended protein. Although these alterations are possible, researchers found that they rarely occur, as heat sensing would not be needed in these animals. Rodents and humans could not have any modification, which suggests that vampire bats are more closely related to cows, dogs, and moles than rodents. It is also noted that zebrafish have an altered TRPV1 which increases their sensitivity to heat, although the alteration is achieved through a different mechanism than the vampire bat. This discovery demonstrates the ability of unrelated animals to evolve similar traits.
The ability of the vampire bat to locate and feed off of warm blood is something that has fascinated humans, which is reflected in the use of vampires in fiction. These researchers have started to unveil the secrets behind this creature’s unique feeding habits. This study demonstrates that without even changing the sequence of DNA, a new function can be created, such as sensing heat to help in the feeding process. Moving forward, other mechanisms of protein modification could be compared to determine relatedness of different species. It could also be investigated which modification provides the greatest heat sensitivity between bats, snakes, and zebrafish.
Gracheva, EO et al. 2011. Ganglion-specific splicing of TRPV1 underlies infrared sensation in vampire bats. Nature. 476: 88-92.
TRPV1 transient receptor potential cation channel, subfamily V, member 1 [ Homo sapiens ] [Internet]. NCBI. [updated 2011 Oct 30; cited 2011 Nov 7]. Available from: http://www.ncbi.nlm.nih.gov/gene/7442