(I first saw this article on 10/31 (how apropos!) but did not get a chance to write about it until today.)
Vampire bats are small winged mammals which live in the tropics of North and South America and gorge on blood from birds and livestock. New research has identified some of the genetic changes which allowed the vampire bat to evolve to subsist on a diet of pure blood.
These bats have made modification to the plasminogen activator – a gene that helps other animals (e.g. humans) produce proteins that bust up blood clots and clear vessels.
There are three species of vampire bats. Hairy-legged vampire bats feed on birds, while the white-winged vampire bats prey on both birds and mammals. One species (the common vampire bat) feeds exclusively on mammals; it prefers cattle but also is known to bite humans.
The plasminogen activator gene of the hairy-legged vampire resembles most the PA a closely related non-vampire bat. It seems that activating PA in saliva is enough to keep the bird blood flowing while it feeds.
The other two species that prey on mammals have an additional acquired mutation that prevent ther PA proteins from being silenced by a natural inhibitor. It appears that feeding on mammals was a key adaptation.
According to the scientists who made the discovery, the common vampire which feeds only on mammalian blood has also acquired several copies of the PA gene. “Two copies seem to be under tight evolutionary selection not to mutate, underscoring their biological importance.”
However, it’s possible that the copied genes are in the process of repurposing themselves. Or the genes could be atrophying from lack of use.
According to the article, there were probably other adaptations that evolved into the vampire bat. The first vampire bats emerged about 26 million years ago and are closely related to insect-eating bats.
“Vampire bats have very sharp incisors that erupt out of their mouths. Their tongues contain a specialized groove that allows a blood-meal to flow via capillary action, not sucking or slurping.”
To determine how these features evolved will quire a full sequencing of the vampire bat’s genome, which may happen within sometime soon.
Full article can be found here: http://www.newscientist.com/article/dn15083-how-vampires-evolved-to-live-on-blood-alone.html