The thought of it will certainly not particularly amuse many people. But our face and nipples are home to countless tiny eight-legged creatures that have settled in the hair follicles: hair follicle mites (Demodex folliculorum) are so intertwined with us that they could be on the way from parasite to true symbiote. This is suggested by a study by Alejandro Manzano Marín from the University of Vienna and his team in Molecular Biology and Evolution.
The research group had analyzed and sequenced the genome of the eight-legged friends. The result: as a result of inbreeding and isolation on our bodies, the mites, which are only 0.3 millimeters in size, have eliminated more and more genes and cells over time and have thus developed into an organism that is already significantly reduced. “They survive with a minimal repertoire of proteins – the smallest number that has ever been observed in this and related species,” says Manzano Marín.
The hair follicle mites feed on the sebum secreted by the hair cells in the pores. They are particularly active at night; then they move between the follicles, looking for mating partners. However, they cannot survive permanently outside the pores. The study also found one reason for the nocturnal activity: Among other things, the microorganisms have lost their UV protection gene and the so-called timeless gene, which is responsible for other living beings waking up in daylight. Instead, they are awakened by the melatonin that we release at night.
© Alejandra Perotti, University of Reading (detail)
mite in pore | Microscopic image of one stuck in a skin pore Demodex folliculorum-Mite.
Manzano Marín and Co also refute the assumption that the mites do not have an anus. According to this, her body would fill up with feces during her short life. If they then die, it would be released, which could lead to skin irritation. In fact, however, the animals have an excretory organ and regularly release their digestive products. They may even ensure that the skin pores are clogged less often.