Vampire bats adapted to drinking blood by shedding several genes

Genes lost during vampire bats’ evolution may have helped them to adapt to their exclusive blood diet which is high in iron and fluid and low in calories

By Alice Klein

Vampire bats are missing several genes found in other bats, which may be related to their unique diet – they are the only mammals that feed exclusively on blood.

Living on blood is challenging because it is mostly composed of water and low in calories. To get the energy they need, common vampire bats (Desmodus rotundus) have to ingest as much as 1.4 times their body weight in blood during each meal.

Previous studies have uncovered some of the ways that vampire bats have adapted to their diet. For example, they have heat sensors in their face to detect victims’ blood vessels, sharp teeth to pierce them and anticoagulants in their saliva so they can drink blood without it clotting. They also have unusually large, stretchy stomachs for storing all the ingested fluid.

To find out more, Moritz Blumer at the Max Planck Institute of Molecular Cell Biology and Genetics in Germany and his colleagues sequenced the common vampire bat genome and compared it with the genomes of 26 other bat species.

They discovered that the vampire bats are missing 13 genes that are found in other bats. The loss of these during their evolution may have occurred as they adapted to their unique diet, says Blumer.

For example, three of the lost genes are responsible for taste receptors that tell different foods apart, which is redundant if you only feast on blood.

Two other genes that the bats have shed are normally involved in managing blood sugar levels – called glycaemic control. “We think that the blood diet of vampire bats is so limited in carbohydrates that vampire bats have lost normal glycaemic control,” says Blumer.

The loss of another gene – REP15 – may have occurred to allow the vampire bats to increase the amount of iron they can excrete, since their iron-rich blood diet puts them at risk of becoming overloaded with the mineral. One estimate suggests that a vampire bat’s relative iron intake is 800 times higher than ours.

The researchers also found that the bats are missing a gene called CYP39A1, which may explain their sophisticated social and cognitive skills. The loss of this gene boosts a chemical called 24S-hydroxycholesterol, which has been shown to enhance learning and memory.

“Vampire bats are especially dependent on such advanced social behaviour, as it helps them to cope with the negative consequences of their carbohydrate-poor blood diet,” says Blumer. For example, the animals commonly share regurgitated blood with roost mates that haven’t been able to find a nightly meal, suggesting a high degree of social cooperation, he says.

Journal reference: Science Advances, DOI: 10.1126/sciadv.abm6494