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Saturday, May 18, 2024

Ask Mr. Scientist: Earthworms and wrinkly fingers

Dear Mr. Scientist,

After all this rain, the sidewalks are covered with worms. I’ve heard before they do this to avoid drowning in their water filled tunnels. Is this true?

—Kevin M.

This is a common misconception, and for a while, even scientists thought this was true. Earthworms can actually survive for several weeks under water, so this isn’t the case. The actual reason is it’s easier for worms to crawl across the ground than tunnel under it. Normally, this isn’t possible because earthworms must keep their skin moist in order to absorb oxygen (they don’t breathe with lungs like we do) and would dry out if they spent too much time above ground. This is why they stay underground where they are surrounded by moist soil. When it rains though, there is water everywhere, and the worms are able to survive above ground…at least until the rain stops.

Dear Mr. Scientist,

Why do a person’s fingers get all wrinkly after they get wet?

—Helen T.

After as little as five minutes of constant exposure to water, the blood vessels in the fingers and toes constrict and pull sections of skin inward. As a result, the skin wrinkles and your fingers and toes take on the familiar pruney appearance one gets from spending too much time in the tub. Interestingly, people who have suffered nerve damage to their digits do not exhibit this phenomenon. This peculiarity led a researcher to investigate this situation further and found fingers are able to grasp wet and slippery objects better when they are wrinkled. This wrinkling business may be an actual evolutionary adaptation instead of a weird body quirk.

Ask Mr. Scientist is written by Michael Leitch. If you have a burning science question you want him to answer, tweet @DC_Science or email it to

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