London, Oct 31: A new research has pinpointed some of the genetic changes that allowed vampire bats to evolve to subsist on a diet of pure blood.

According to a report in New Scientist, key among those changes is a knack for keeping their meals from coagulating, which they do with the help of a gene found in other animals – plasminogen activator.

In humans, the gene protects against heart attack by producing proteins that bust up blood clots and clear vessels.

Previous research had shown that vampire bats activate the gene in their saliva, too.

However, the small, winged mammals, which live in the tropics of North and South America and gorge on blood from birds and livestock, have made other modifications to plasminogen activator (PA) since they split off from fruit and insect eating bats, according to David Liberles, a geneticist at the University of Wyoming in Laramie.

His team studied three species, each with its own take on vampirism.

Hairy-legged vampire bats victimise only birds, while its cousin, white-winged vampire bats, prey on birds and mammals.

Just one species, the common vampire bat, feeds exclusively on mammals. It prefers to bleed cattle and other livestock, but humans– especially who sleep outside – also fall victim to its bite.

Of the three, the hairy-legged vampire bat’s PA gene looks most like that of closely related, non-blood-feeding bat species.

“Activating PA in saliva could be enough of a change to keep bird blood flowing freely,” Liberles said.

The two species that prey on livestock acquired additional mutations that prevent their PA proteins from being silenced by a natural inhibitor – a process that humans and other mammals use to put a harness on blood clotting.

“Feeding on mammals was a key adaptation,” Liberles said.

Common vampire bats, which feed only on mammalian blood, have also acquired several copies of the PA gene.

According to Bruce Patterson, a zoologist at Field Museum in Chicago, additional adaptations undoubtedly played an important role in the evolution of vampirism.

The first vampires, which emerged less than 26 million years ago according to fossil records, are closely related to insect-eating bats that may have gorged on the parasites of prehistoric beasts.

“Once you’re pulling insects off of a mammal, it’s a very small step to going after the blood,” he said. (ANI)