DNA reveals how mites are forming an evolutionary partnership with humans

You probably already knew that you had mites living on your skin feeding off your dead skin cells. These tiny beings even use your skin for reproduction.

A new study finds that one species of mite is evolving from parasite to partner in an evolutionary relationship with humans, according to a press release by the University of Reading published on Tuesday. 

From external parasites to internal symbionts

"The first ever genome sequencing study of the D. folliculorum mite found that their isolated existence and resulting inbreeding is causing them to shed unnecessary genes and cells and move towards a transition from external parasites to internal symbionts," said the statement.

In other words, these organisms are slowly but surely merging into a symbiotic system with us.

“We found these mites have a different arrangement of body part genes to other similar species due to them adapting to a sheltered life inside pores. These changes to their DNA have resulted in some unusual body features and behaviors," said Dr. Alejandra Perotti, Associate Professor in Invertebrate Biology at the University of Reading, who co-led the research.

What else do we know about these mites?

They are extremely simple organisms with tiny legs powered by just 3 single cell muscles and survive with the minimum repertoire of proteins – the lowest number ever seen species like this one.

They tend to exhibit nocturnal behavior as they lack UV protection and are unable to produce melatonin. However, they are able to fuel their all-night mating sessions using the melatonin secreted by human skin at dusk.

They have a unique mating procedure. The males have a penis that protrudes upwards from the front of their body meaning they have to position themselves underneath the female when mating and both have to cling onto human hair.

They have many more cells at a young age compared to their adult stage and may be on the path to extinction as they lack exposure to potential mates that could add new genes to their offspring.

Wrongfully accused 

Previous studies had speculated that the mites do not have an anus and therefore must accumulate all their feces through their lifetimes before releasing it when they die, causing skin inflammation. The new study, however, confirmed they do have anuses and so are not to be blamed for skin irritations.

“Mites have been blamed for a lot of things. The long association with humans might suggest that they also could have simple but important beneficial roles, for example, in keeping the pores in our face unplugged," concluded Dr. Henk Braig, co-lead author from Bangor University and the National University of San Juan.