National Geographic : 2015 Feb
86 national geographic • february 2015 at least a million, but no one knows enough to say with confidence, nor will anyone know for decades. Museum collections are filled with mite species no one has yet had a chance to study. Some undoubtedly offer fascinating evolutionary stories. Others eat herbivorous insects and could benefit agriculture or medicine. Still others may be vec- tors for deadly pathogens. Another reason for my bet: Mites are special- ists that occupy every conceivable niche, includ- ing the trachea of bees, the shafts of feathers, the anuses of turtles, the stink glands of bugs, the digestive systems of sea urchins, the lungs of snakes, the fat of pigeons, the eyeballs of fruit bats, the fur around vampire bat penises. Liv- ing in these habitats necessitates special hairs, chemicals, foot pads, mouthparts, and tricks. It also requires a way to get from one patch of good habitat to the next. Some mites ride from flower to flower in the nostrils of hummingbirds. When the bird hovers at a flower, the mite sniffs the blossom to see if it’s the right kind for finding a mate among the petals. If it is, the mite runs down the bird’s beak at speeds that are, in terms of body lengths trav- eled, some of the fastest on Earth. Other mites hitch rides on the backs of beetles or ants; some fly in the ears of moths. One spe- cies of mite hangs on to the hind foot of the army ant Eciton dulcius, and its hind legs serve as surrogates for the ant’s own claw. Others float through the clouds or on loops of silk that they produce and unfurl into the wind. All of this is to say that if one can imagine a habitat, however narrow, mites are there, even if that habitat is hard to reach on legs just microns long and a tenth the thickness of a human hair. Yet the marvels of mite transport pale in com- parison with the idiosyncrasies of mite repro- duction. Some clone themselves. Others eat their mothers. Others mate with their sisters while still inside their mothers and then, during birth, kill their mothers. In the nostrils of humming- birds and the ears of moths lurk Greek tragedies of small, strange lives. The habitats that offer mites the most advan- tages are bodies, whether of mammals, birds, insects, or any other creature larger than a mite. Bodies are the buffet bus of life, providing food and transportation. Mites that live on bodies are specially adapted to hold fast to their host, even when it runs, swims, or flies. Most bird species host more than one special- ized mite found nowhere else. One species of parakeet has 25 different species of mites living on its body and in its feathers, each in a differ- ent microhabitat. Rabbits host several species of mites, mice as many as six. Even seals have their own mites. Given such diversity and specialization, it’s easy to imagine that a roomful of people (think of all the habitats!) would be fertile ground for discovering mites—and for making good on my bet. For a long time this was just a conversa- tion starter at slow parties. But recently some collaborators and I gathered a group of folks and asked them to sample their own skin. After some swabbing, poking, and DNA sequencing, we found mites on every adult we sampled, in- cluding one species new to science that seems to live mainly on people of Asian descent. Think of it: A mite that probably lives on millions of humans, maybe even billions, and yet it was to- tally unknown until that moment. I was thrilled. How did mite systematists—scientists who name new species—respond? A few were ex- cited; the rest shrugged. They knew that my bet for mite diversity was an easy one, a fact of life they witness every time they examine a scoop of soil, peer into moss, or swab a friend. In fact, one need look no farther than the mites pictured in this article, most of which are unnamed spe- cies. In all likelihood they will long remain that way, mysteries in plain view, like most of life. j MORE ONLINE ngm.com/more VIDEO INTERVIEW Your Face: Mating Ground for Mites A Scientist and His Art Photographer Martin Oeggerli talks about how he creates and colors his images and why he refers to himself as a “micronaut”—an astronaut for the microcosmos.