How do vampires survive by drinking blood?

Don’t listen to Bram Stoker, the Irish writer who wrote the novel Dracula: blood is not life, at least not in the sense in which the Transylvanian count understands it. Let’s be clear: as a vehicle for transporting oxygen to cells and carbon dioxide, it works perfectly. How about food, though? It is very bad and not very nutritious, and it is no coincidence that (almost) there are no mammals whose diet is exclusively blood-eating. The exception to the rule are vampires, three bat species native to the American continent and which are the only mammals to feed exclusively on blood.

Differences … But if it’s true that plasma as food isn’t that great, how do vampires survive? The answer comes from a Science Advanceswhich reveals what the genetic differences are between vampires and other bats, and what they entail for their diet.

Blood, explain the authors of the study who compared the genome of the three vampire species with that of 26 other species of bats with a “normal” diet (insects, fruit, nectar, meat), is a demanding food: it is composed for 78% of liquids, has a very low calorie content and the few nutrients it contains are mostly proteins (93%), with very few fats and carbohydrates.

Adaptation. Consequently, vampires have had to adapt: ​​their stomach, for example, has changed to become a sort of soft and easily expanding pouch, to contain all the blood that the animal can drink from a single prey. The fact that the blood contains so little fat and carbohydrates means that vampires are unable to stock up for the winter, and are particularly sensitive to fasting: 48 hours without eating are enough to bring them to death.

All these adaptations are a reflection of the genetic differences identified by the team led by Moritz Blumer of the Max Planck Institute in Dresden: compared to their bat relatives, vampires have lost or de-activated 13 genes.

The loss of function of these genes is in turn linked to changes in the physiology and metabolism of vampires compared to other bats; without going into too technical details, take the example of the gene called REP15: its loss has improved the ability of vampires to expel excess iron, which is an important component of blood and is therefore taken in large quantities.

Each of the 13 lost genes has some reflection on the differences between vampires and bats (and all other mammals, actually), and is a piece of the puzzle that allows these animals to feed exclusively on blood.

Obviously their adaptation has not only genetic basis: vampires also have an intense and very collaborative social life, so if an individual of a colony is hungry because he has not been able to find a prey to “suck”, the other members will help him. regurgitating some of their meal.

The consequences. This behavior in turn has physiological consequences: as demonstrated by another recent, published study last November in Biology Lettersvampire colonies have a “social microbiome” – in other words, the bacteria that live in their gut digestive tract are very similar to each other within the same colony, an important advantage when sharing the same food.

How do vampires survive by drinking blood? –