Intertidal Organisms EZ-ID GUIDES


on this species


Halosydna brevisetosa (Eighteen-scaled worm)

photo of eighteen scaled worm
Copyright © 2007 Mary Jo Adams

This species can be either free living or coexist commensally with other invertebrates, most commonly in the tubes of tubeworms.  The eighteen pairs of overlapping scales (elytra) it bears on the dorsal surface make it easy to identify.  This is the only species of scaleworm in the Pacific Northwest adorned with 18 pairs of elytra.  Scales are sometimes lost but can be replaced in as little as 5 days.  Color is variable but it frequently has black and/or white spots on the scales.  When free living, it attains a length of 3 inches (8 cm.) but gets larger, to 4 inches (11 cm) when living as a commensal organism.  The eighteen scaled worm can be found from the mid-intertidal to a depth of 1800 feet (545 m.).  Look for it on rocky beaches, among mussel clumps, and in the root masses of sea grasses.  It is a predator and feeds on other worms.    

This species is also known under the scientific name Polynoe brevisetosa and the common name armored scaleworm.    




This page was created by Mary Jo Adams on 11/7/08.