July 1, 2015

Bristle worms get their turn

Tomoptorid worm

Tomopterid worms are active swimmers, using their large, paddle-shaped parapodia to propel themselves through the water. They are voracious predators that chase and eat other, smaller midwater animals. Although their bodies are transparent, this species has red pigments in its digestive system, perhaps to hide any glowing prey that the worm may have eaten. If attacked, worms themselves glow, creating swirling constellations of glowing yellow spots to distract predators

An amazing variety of bristle worms thrive in the ocean, both on the seafloor and up in the water column. Biologists call these worms polychaetes (pronounced “polly-keets”), which means “many small hairs” in Latin. Polychaete worms have segmented bodies, with each segment sporting many little bristles (chaetae). The bristles serve different purposes in different worms, from crawling to swimming to defense.

Scientists have named over 8,000 species of polychaete worms, but they have hardly scratched the surface, especially when it comes to worms in the deep sea. Over the past decade some of the most amazing animals named by MBARI researchers have been polychaete worms.

A variety of polychaete worms

Illustration of marine worms from “Das Meer” by by Matthias Jacob Schleiden, 1804-1881. Image: NOAA photo library.

Worm expert Karen Osborn was a graduate student at MBARI and is now a curator at the Smithsonian’s National Museum of Natural History. She and other worm experts recently decided to designate July 1st as International Polychaete Day in honor of Kristian Fauchald, a distinguished polychaete taxonomist who passed away on April 5, 2015. Having spent over 50 years working in the field, Fauchald had a huge impact on several generations of researchers. As an indicator of the respect he elicited from his fellow scientists, Fauchald has had almost 40 species of worms named after him.

Osborn said that she always admired Fauchald’s “enthusiasm for polychaetes, for people, and for living life to the fullest. For this reason, Osborn said, “We decided to launch International Polychaete Day to share with the world these amazing animals, which Kristian found so fascinating”.

Polychaete expert Kristian Fauchald

Polychaete expert Kristian Fauchald studying worms in a salt marsh. Image: Dane Penland, Smithsonian Institution.

Polychaetes have evolved into a multitude of sizes and shapes, from small, round “gumball worms” to two-meter-long, centipede-like pile worms. They can be completely transparent or white, blue, green, red, yellow, orange, purple, and every color in between. They occur in every marine habitat, from shallow tide pools to volcanic hydrothermal-vent chimneys. Many of them glow. They are fabulous recyclers and builders, creating massive reef structures and tangles of tubes that house a myriad of other animals including crabs, snails, and (of course!) other worms. They are not only beautiful but also essential to the health of the world ocean.

Here are some examples of the bizarre and wonderful polychaetes that MBARI researchers have seen in the ocean depths. For more information and images, see the International Polychaete Day posts on Twitter and in a blog by the National Museum of Natural History.


Like tomopterids, worms in the genus Swima swim freely in the depths of Monterey Canyon, undulating their bodies and beating their parapodia. Their sharp spines may help protect them from predators. When disturbed, some species release small oval sacs of bright green, glowing fluid that may startle or distract predators, earning them the nickname

Swima worm: Like tomopterids, worms in the genus Swima swim freely in the depths of Monterey Canyon, undulating their bodies and beating their parapodia. Their sharp spines may help protect them from predators. When disturbed, some species release small oval sacs of bright green, glowing fluid that may startle or distract predators, earning them the nickname “green-bomber worms”


Flota worm: A relative of the Swima worms above, worms in the genus Flota are free-swimming, but are often seen near the deep seafloor, more than 1,500 meters below the surface. They propel themselves by moving their bodies, parapodia, and spines. They emit a scintillating blue glow, but scientists are not sure how this helps them survive in the depths.

Flota worm:
A relative of the Swima worms above, worms in the genus Flota are free-swimming, but are often seen near the deep seafloor, more than 1,500 meters below the surface. They propel themselves by moving their bodies, parapodia, and spines. They emit a scintillating blue glow, but scientists are not sure how this helps them survive in the depths.


Poeobius worm

Poeobius worm
This polychaete worm in the genus Poeobius hardly looks like a worm at all. But it is one of the most common inhabitants of the depths of Monterey Canyon. Poeobius drifts through the water, collecting bits of sinking organic matter in a mucus net and then eating them. When disturbed, it reveals its wormy nature, wriggling vigorously.


This new MBARI video highlights polychaete worms that drift and swim in the midwater, deep below the ocean surface.


This YouTube video shows polychaete worms and other animals that eat the bones of dead animals on the deep seafloor.


Here’s a YouTube video showing giant, two-meter-long polychaete worms at hydrothermal vents in the Gulf of California

For additional information or images relating to this article, please contact: Kim Fulton-Bennett
831-775-1835, kfb@mbari.org