A Tomopteris helgolandica worm caught in the North Sea.

  • Taxonomy

    Kingdom: Animals

    Phylum: ringed worms (Annelida)

    Class: Bristleworms (Polychaeta)

    Order: Aciculata

    Family: Tomopteridae

  • Location

    Mainly on open sea, sometimes in coastal or brackish waters.

  • Size

    Females up to 10 cm long, males up to 6 cm long.


Most bristle worms found in coastal plankton are larvae of bottom dwelling worms, but there are some families that are completely adapted to life in free water, such as the worms of the genus Tomopteris. These are beautiful, bizarre animals that can also grow very large. 

Tomopteris are almost transparent. The first and second segment of the body is merged into two palps. The worms have two eyes. The next segment contains a few very long sensory hairs.  The next segments consist of paddle-shaped outgrowths (parapodia) with which the worm can swim fast. These parapodia can produce a yellowish light (bioluminescence). The species Tomopteris helgolandica, common in the North Sea, has a long tail that most related species miss.

Biology and ecology

Tomopteris are real predators. With their protruding proboscis (see photo) they can catch large prey such as fish larvae, arrow worms and appendicularia. 

Some species can excrete luminous particles when disturbed to confuse their attacker. The peculiarity of bioluminescence in Tomopteris is that the light is yellow, while most other luminescent marine animals produce different colours of light. 

Very little is known about the way of life of Tomopteris and related worms. Personally, I think it is one of the most extraordinary animals you can encounter!

A Tomopteris helgolandica worm caught in the North Sea.

Head of the same Tomopteris worm on which the two eyes are clearly visible. Inside the head you can see the proboscis, which can be protruded to catch prey.