Just in time for Halloween: I came across a preprint in bioRxiv that identified 13 genes missing from vampire bats (Desmodus rotundus), but found in other bat species. Animals that drink blood, or sanguivores, have to deal with a diet that is high in protein but typically lower in fat and sugar. Many of the missing genes are thought to be related to their ability to drink blood and obtain necessary nutrients, while avoiding toxic effects related to the high iron content of their meals.
Granted the study has not yet been peer-reviewed, the data show that genes related to the ability to taste sweet and bitter flavors have been lost in these bats. Other missing genes are related to the secretion of insulin, which is thought to help keep blood sugar levels stable given their relatively low carbohydrate diet. In addition, they are missing a gene important to inhibiting the protein-digesting enzyme, trypsin, which may help them digest their high protein meals. Moreover, missing genes related to iron excretion could also help the animals excrete the metal and avoid poisoning.
I wonder if Dracula is also missing these genes…