The Mites Among Us

Let’s take a closer look at one of the parasites that live on our bodies. A species of microscopic mite (Demodex folliculorum) lives in the pores on our face, as well as in facial hair follicles, including the eyelashes. They are an invisible 0.3 millimeters long and are passed on to us at birth. They mate – right there on our faces – at night.

Now biologists have sequenced the genome of D. folliculorum for the first time. They learned that because of the mite’s isolated existence, with no exposure to external threats or mixing with other genetically distinct mites, they are evolving into extremely simple creatures – with wee legs powered by just three single-cell muscles, for example.

The gene depletion also explains why these little beasts are nocturnal:  they have no UV protection and have lost the gene that causes animals to be awakened by sunlight; and they can’t produce melatonin, so they use the melatonin we humans secrete on our skin at dusk. That’s how they fuel their nocturnal orgies.

All this inbreeding and lack of genetic variety could put the mite on a path to extinction, or at least move the species into a transitional state, from  parasite to symbiont, which would entwine them even closer to their human hosts. What do we get from the deal? It’s believed that these guys help keep the pores in our face unclogged. Keep up the good work, fellas.

The research appears in the journal Molecular Biology and Evolution.

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