Harmothoe imbricata (Linnaeus, 1766)
Common name(s): Fifteen-scaled worm, Free-living scaleworm
|Synonyms: Aphrodita imbricata|
|Harmothoe imbricata, about 3 cm long. A few of the anterior elytra have fallen off this individual, revealing the segments underneath. This individual was living within the tube of another polychaete in Fidalgo marina.|
|(Photo by: Dave Cowles, July 2009)|
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.
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
Habitat: 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.
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
robusta, and Diopatra ornata.
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Lamb and Hanby, 2005
O'Clair and O'Clair, 1998
General Notes and Observations: Locations,
abundances, unusual behaviors:
This oblique view of the head shows the posterior eyes, which are visible dorsally, plus the anterior pair of eyes which are covered over by a flap of the prostomium. The two lateral prostomial antennae are seen to be inserted ventral to the median antenna. The anterior elytra were removed for this view.
The elytra are fringed with fine papillae, especially along the posterior edges (to the right in this photo).