Fifteen Scaled Worm

How to Distinguish from Similar Species: Several other species of Harmothoe have anterior eyes that are visible dorsally. Other Polynoids may have other numbers of elytra.

Biology/Natural History: This scaleworm is very common in some parts of its range, such as California and SE Alaska. It is an active swimmer and can live in a wide range of salinities. The species is a predator which lies in wait, then pounces on its prey, using its large, jawed proboscis to subdue them. Amphipods are common prey. It also eats some algae. The pink eggs are released from the nephridiopores. In some areas, females of this species brood their eggs under the elytra; in other places they do not seem to do so. Brooding in our area usually takes place in summer. Larvae may have a long pelagic period or direct development. Polychaetes this species may live commensally with include Thelepus crispus, Neoamphitrite robusta, and Diopatra ornata.

Lives in a wide variety of habitats: Freeliving intertidally under rocks and in eelgrass; subtidally in kelp holdfasts or mussel beds. May live commensally with echinoderms or other polychaetes.

Geographical Range: A very widely distributed species. Found throughout the northern hemisphere. Point Barrow, Alaska to s California on our coast.

Depth Range: Low intertidal to 3710 m

As with other members of Family Polynoidae, the dorsal side of this species is covered with a series of platelike elytra. Harmothoe imbricata has 15 pairs of elytra which cover nearly all the segments. The elytra have a light fringe of papillae around the edge. There is only one basic kind of notoseta and one kind of neuroseta on any given segment. Most of the neurosetae fork at the tip. The notosetae are thicker than the neurosetae. One pair of eyes is visible dorsally, but the anterior pair of eyes cannot be seen except from the side. The lateral prostomial antennae are inserted ventrally to the medial antenna. Color highly variable, though brown is common.