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Home > Research & Collections > News > Meet a Polychaete

Meet a Polychaete

Get to know this fascinating marine worm

In this full view of the polychaete worm Syllis stewarti, you can see the head on the left, and its rear end (complete with blue tint) on the right. Photo by NHMLA Polychaete Collections Manager Leslie Harris.


Have you ever seen a polychaete (pronounced poly-keet)? Polychaetes are fascinating and colorful worms, nearly all of which live in the ocean. There are more than 10,000 described species (and probably lots more), and they can be found in every habitat in the ocean, from tidepools to the deepest ocean floor and everywhere in between. Many are found in the sand and mud, but some spend their whole lives swimming — yes, swimming! — in the open water. These worms can do it all.

a closeup photo of a worm called Syllis stewarti, which is pink with lots of little segments. down its body is a whitish area of its body.
The lightly colored section of this worm’s body is called a proventricle. It’s a cylindrical organ with rows of muscle cells that functions like a pump, creating enough suction to pull the worm's food into its mouth and down its digestive tract. Photo by Leslie Harris.

This particular worm from the NHMLA Polychaete Collections is Syllis stewarti. It was first described in 1942 but has rarely been seen since. Last summer, though, NHMLA Polychaete Collections Manager Leslie Harris found some on a vertical rock in the upper tide pools of Friday Harbor, Washington.  

The worms weren’t alone. They were wrapped around black leather chitons (a species called Katharina tunicata), relatives of clams with eight interlocking hard shells covering their soft bodies.

a scene in a tide pool with a chiton in the middle, above which is a small worm
The polychaete worm is just below the blue arc. Photo by Leslie Harris.

Interestingly, each worm's head was inserted into the mouth of one of these chitons, possibly so the polychaetes can eat some of the chitons’ food. Stealing food from other organisms like this is called kleptoparasitism (but others just call it rude), and it’s an unusual behavior for these worms. Only one other worm species in this polychaete family — specifically, family Syllidae — is a known kleptoparasite, and that one steals its meals from corals. The rest of these worms, we assume, have figured out how to find their own dinner.


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