.
.
.
.
.
.
NewScientist.com news service
Ewen Callaway
Any mad scientists planning to genetically engineer Dracula this Halloween should look to the vampire bat for inspiration. New research pinpoints some of the genetic changes that allowed them to evolve to subsist on a diet of pure blood.
Key among those is a knack for keeping their meals from coagulating. They do so 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, says 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.
Gorging on blood
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 says.
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 says.
Common vampire bats, which feed only on mammalian blood, have also acquired several copies of the PA gene, though Liberles’ team isn’t exactly sure why. Two copies seem to be under tight evolutionary selection not to mutate, underscoring their biological importance.
Yet in many organisms copied genes are free to take on new chores, and the other PA genes could be in the process of repurposing themselves. Alternatively, these genes could be atrophying from lack of use.
Additional adaptations undoubtedly played an important role in the evolution of vampirism, says Bruce Patterson, a zoologist at Field Museum in Chicago.
Rise of the vampires
The first vampires, which emerged less than 26 million years ago according to genetic evidence, 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 says.
Unlike other bats, vampire bats boast knife-sharp incisors that erupt out of their mouths. “You can actually cut yourself handling a bat skull in a museum, they’re that sharp,” Patterson says. Their tongues contain a specialized groove that allows a blood-meal to flow via capillary action, not sucking or slurping.
“They’re absolutely amazing animals,” he says.
One challenge to determining when and how these features evolved is the lack of genetic data on vampire bats, Liberles says. One sequencing centre is already at work on the genome of the little brown bat.
“A vampire bat genome project would be great,” Liberles says.
Although he knows of no such project in the works, the breakneck pace of advances in gene sequencing technology means that it’s a matter of time before scientists crack the instruction book to becoming a vampire bat.
That leaves human gene targeting – a key step in genetic engineering – as the final hurdle to creating your very own Nosferatu.
.
.
.
Journal reference: Naturwissenschaften (DOI: 10.1007/s00114-00800446-0)
Reference: http://www.newscientist.com/article/dn15083
.
.
.
