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Ubiquitous yet unseen, tiny mites
loom large in Desch's research
March 8, 1999
he tiny, elongated creature seen through a microscope resembles a tadpole with a very long tail, all its other important body parts crammed at the head end. Eight stubby, clawed legs feebly grope in the immersion oil.
Clifford Desch looks through the binocular eyepiece, then announces that the creature is female. He moves the slide and finds a male, then roams further and spots a larva. It resembles a medieval mace, with the spikes filed down to knobs.
Desch is an acarologist - that is, a biologist who studies mites - in the Department of Ecology and Evolutionary Biology who teaches Introductory Biology for Science Majors at the Hartford campus. He also does research for the entomology department of the University of Massachusetts at Amherst.
The creatures he was looking at are Demodex folliculorum, a near-microscopic species of mite found in the pits of human facial hair follicles. To get the sample, he had dragged the bent end of a bobby pin across his own forehead and wadded the evicted mites and some skin oil into a tiny blob.
Mites are tiny relatives of spiders. Except for ticks, which are a type of mite, most mites are microscopic, or nearly so. They swarm all over the planet, as ubiquitous as bacteria, but are scarcely noticed unless they cause trouble, such as triggering asthma attacks or decimating honeybee colonies. There are 140,000 recognized species of mite, and these are probably no more than 5 percent of the total number of species.
Mites are so supremely adapted and adaptable that they're here to stay as long as the world lasts, Desch says. He has published papers on mite specimens sent to him from all over the world by veterinarians, zoo personnel, wildlife biologists and scientific collectors, along with specimens he's garnered on his own. He has studied mites from hosts as varied as koalas, vampire bats, snow leopards, red squirrels, Asian rats, fruit bats, black bears, Chinese striped hamsters, armadillos, Tasmanian devils, and New Zealand short-tailed bats.
An article in the December 1998 issue of National Geographic magazine about mites and other external parasites that live on humans is based on Desch's research.
While Desch was working toward his Ph.D. in zoology at UMass, his adviser was William B. Nutting, the now-deceased world expert on hair follicle mites. Nutting's enthusiasm soon infected the young Desch and propels him still. Desch's main interest within acarology is taxonomy, or describing and classifying species, a job that for mites and ticks has scarcely begun.
Ticks are a more familiar kind of mite because many species are large enough to be easily visible, often ballooning when they load up with their preferred food, blood. Desch shows a preserved, bloated specimen of the world's largest tick species, the size of a large grape, that was plucked from a sloth. The creature's eight black, wiry, many-jointed legs, like snippets of miniature barbed wire, add to the horror.
Demodex mites have no eyes, no respiratory apparatus, no anuses. Nitrogenous wastes are kept in a growing crystallized mass within its body, never expelled lest they foul the cramped quarters where the mites live out their days. A mite dies still carrying the waste mass, and the tiny corpse, crystals and all, is expelled from the follicle by the outward flow of sebaceous oil.
Mites are so small, they have no elaborate respiratory apparatus, but merely exchange gases through their body walls. Males and females are born, live, feed, mate, die, and females give birth all within a hair follicle. A fertile female produces only one egg at a time, a third as long as herself. Since space and food are limited in this minute environment, no mass egg production is necessary.
Desch studies mites, he says, because "they fascinate me. They live everywhere, in almost every habitat. They're very small, but they've got all the same parts anything bigger has. There's also the adventure of discovering species never seen before. I have discovered new mite species right around here in Connecticut and Massachusetts."