How a Tick Does Its Dirty Work

SCIENCE

How does a tick simultaneously cut through skin and embed an often-toxic anchor? It sinks its teeth into the situation. When seen with an electron microscope, a tick’s mouth has what look like twin saws flanking an appendage that appears to be the kind of long, barbed sword that a villain in a video game might favor. (New York Times, be sure to watch the video!)

Use our resources to get an up-close view of ticks and other tiny terrors.

This deer tick has been magnified about 90 times, enough to see the barbed hypostome protruding from its mouth.  Photograph by Darlyne A. Murawski, National Geographic 

This deer tick has been magnified about 90 times, enough to see the long, barbed hypostome protruding from its mouth.
Photograph by Darlyne A. Murawski, National Geographic

Discussion Ideas

  • A tick’s chelicerae have starring roles in the New York Times article and video. Chelicerae (pronounced kuh-LIH-suh-ruh) are the “twin saws” that cut through a victim’s skin. How are chelicerae different from teeth? Can you think of other animals that have chelicerae?
    • Chelicerae are mouthparts, part of a tick’s jaw. They are maneuverable and function more like appendages, such as arms or legs, than teeth. (Think about that! Gross.)
    • Many other animals have chelicerae, including horseshoe crabs and, most notably, spiders.
  • Look at our beautiful media spotlight on the chelicerae of a funnel-web spider, “Funnel-Web Fangs.” How are the spider’s chelicerae different from the tick’s?
    • The spider’s chelicerae are smooth, hollow tubes with a sharp end. They pierce the skin of the spider’s victim and deliver the funnel-web’s deadly venom. The tick’s chelicerae are solid and serrated (jagged). They tear through the victim’s skin like saws.
    • The spider’s chelicerae are pointed downward. The tick’s chelicerae are pointed straight ahead.
    • The pointed ends of the spider’s chelicerae are parallel to each other. The serrated edges of the tick’s chelicerae face each other, allowing them to trap and pinch the skin of their victim.
  • Look at our photo gallery of ticks and other tiny creatures with the “Yuck Factor.” (The tick is the fourth image in the gallery.) Why are most of these photos in color, while the electron microscopy used by Nat Geo (above) and the NY Times is black-and-white?
    • The image used in the photo gallery is artificially colored. All images taken with an electron microscope are black-and-white. The “Yuck Factor” section “About Electron Microscope Images” hints at why—the absence of (visible) light in the microscopy process. Our eyes interpret color as a result of a wavelength of light. Electron microscopes use beams of electrons, not beams of light, to magnify their subjects. No light, no color. Let the brainiacs at Cambridge explain it for you: “In the electron microscope, we cannot usually see the effect of the wavelength of the electrons (the ‘colour’) in each image, so we only have ‘black and white’ images. Hence, the information contained in an electron micrograph is solely due to the difference in the flux of electrons through each point in the image—the contrast. The electron microscopist must understand the reasons for contrast in order to gather information from the sample.”

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