DNA tests reveal the omnipresence of two arachnid species living in human skin
Steve Gschmeissner/Science Source
Take a really close look at your face and you’ll probably find that two microscopic relatives of spiders and ticks dwell there. The usually benign mites, Demodex folliculorum and D. brevis, wriggle into skin pores and hair follicles, including eyelashes. And every adult may harbor these hitchhikers, researchers report August 27 in PLOS ONE.
Scientists analyzed DNA from skin gently scraped off the noses and cheeks of 29 North and South Americans. They detected genetic material from Demodex mites in skin samples from all 19 adult subjects and 70 percent of 18-year-olds. In earlier studies, researchers pulled the arachnids off 100 percent of human cadavers but only 10 to 20 percent of the living. The new findings suggest that everyone harbors the mites post-puberty, Megan Thoemmes of North Carolina State University and colleagues say.
Logging the genetic samples in a global mite database revealed that D. brevis mites differ by geographical region: New World mites were genetically distinct from those living in China. If confirmed on a larger scale, the genetics of D. brevismites could provide insight into human migration over millennia.
Editor's Note: This article was updated October 2, 2014 to correct several misstatements: the volunteers were North and South Americans, the younger subjects were 18 years old, and the arachnids were found on 10 to 20 percent of living people in earlier studies.
M.S. Thoemmes et al. Ubiquity and Diversity of Human-Associated Demodex Mites. PLOS ONE. Published online August 27, 2014. doi:10.1371/journal.pone.0106265.
A. Yeager. California mite becomes fastest land animal. Science News. Vol. 185. June 28, 2014, p. 4.