Scientists Say: Nematode

These tiny worms cause disease in humans and plants, but also are important tools for scientists


This print in a rock is not a random curlicue, but a tiny fossilized nematode.

Ghedoghedo/Wikimedia Commons

Nematode (noun, “NEHM-uh-toad”)

Nematodes are tiny roundworms. They live everywhere — from the sea to the soil in your garden. They are usually 2.5 millimeters or smaller, tinier than a single sesame seed. Despite being called “worms,” they aren’t related to earthworms. Instead, nematodes have their own phylum — a related group of living organisms, one of 35 in the Animal Kingdom. Scientists have discovered more than 25,000 species of these worms so far, and use some species in research. Others species help to decompose dead organisms or to kill garden pests. Nematodes also can act as nasty parasites for plants and animals, including people. 

In a sentence

Nematodes have many roles to play on our planet, from plant parasites to useful research tools.

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Power Words

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nematode     A type of roundworm, usually found in soil, that can also live within other creatures as a parasite. It is very small, with no eyes, ears or nose.

parasite  An organism that gets benefits from another species, called a host, but doesn’t provide it any benefits. Classic examples of parasites include ticks, fleas and tapeworms.

phylum     (plural: phyla) A scientific term for a related group of living things. The modern animal kingdom includes about 35 phyla.

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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