Ticks and Mites

Nature Notes by Dr. Frank Lang

I spent an hour or so showing off the Biology Department’s scanning electron microscope to a group of Ashland mid-high science students. They were at the university to celebrate Science and Technology Week. Dr. Jad D’Allura, of the Geology Department, organized the series of tours, as he has for the past several years.

This year we looked at Dermacentor, the dog tick genus, under the SEM, as the scanning electron microscope is called by those of us in the know. We looked at both ends, the back, and the belly for the tick. The head end was the most interesting, though there was some laughter when we examined the other end. I suppose an anus enlarged 4,000 times is enough to cause mirth among middle school scientists. Fortunately I avoided the genital pore. Who knows what might have happened at that sight.

At lower magnifications the hypostome, the mouthpart the tick uses to stay stuck in you while it sucks up its blood meal, appeared to be smooth. Increasing magnification revealed a series of tile-like plates. The tiles all seemed to point toward the back end of the tick. There was absolutely no evidence of left or right threading. The best way to remove a tick stuck in your skin is to have someone pull it gently straight out. Twisting clockwise or counter clockwise will just increase the risk of twisting off the tick’s body leaving the head embedded. Don’t squeeze its body, you may force tick juice, filled with any manner of pathogens, into your bloodstream. Remember when we used to worry about Rocky Mountain spotted fever, Q fever, tularemia, relapsing fever, Colorado tick fever, Powassan encephalitis, and human babesiosis? Now we worry mostly about Lyme disease, though the others are still with us.

In Dermacentor the pair of tiny eyes is located away from what we would call the head. The eyes are more for distinguishing light from dark, rather than forming clear images. The tick’s first leg contains a sensory pore with hair-like structures that sense mechanical and chemical stimuli.

When the middle school scientists and I examined the head end of our dog tick, we discovered two pits in what appeared to be the terminal segment of the pair of antenna-like palps on either side of the hypostome. Each pit contained a structure that looked like a cow’s udder. I did not know what they were, but thought they might be some special sensory organ. I have since learned the structure is the real terminal segment of the palp and that it might perform a sensory function.

Ticks and mites are a separate order in the same class as spiders. There are a lot of them. Some are so specialized that they are known only in the pitchers of our local insectivorous Darlingtonia, others are common inhabitants of house dust. Dust mites can cause major allergies in sensitive humans. The relationship among dust mites, human conjugal relationships, the condom, and runny noses is explained starting on page 135. I’ll bet you can’t wait.

— Dr. Frank Lang

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