Description: As with other members of Family Polynoidae, the dorsal side of this species is covered with a series of platelike elytra scales. Halosydna brevisetosa has 18 pairs of shield-shaped elytra (photo). The elytra are often light brown with white or black spots at the point of attachment. The dorsal chetae are much shorter than the ventral ones, leading to the brevisetosa part of the name. Typically brown or grayish. Often has white or black spots on each elytrum where its stalk attaches to the animal. May have transverse color bands. Up to 11 cm long, but usually 2 cm or shorter if not symbiotic.
How to Distinguish from Similar Species: No other local scaleworms have 18 pairs of elytra.
Geographical Range: Alaska to northern Mexico. Very common in California intertidal.
Depth Range: Intertidal to 545 m.
Habitat: In mussel beds, on floats, seaweed holdfasts, or symbiotic in the tubes of other polychaetes.
History: This very
common predatory species is often found living symbiotically in the
of other polychaetes (especially Terebellids),
on the nudibranch Melibe
leonina where it feeds on the nudibranch's fecal
pellets, or under
clumps of Mytilus
californianus mussels. It often eats other
or eats detritus. When disturbed, it may shed some of its elytra
scales but it can grow them back within a few days. Sexes are separate,
and gonads are found in segments 12-34. The gametes can be clearly seen
through the body wall. The sperm are white and the eggs are pale green.
Fertilization is external, with the gametes released through the
(kidney duct). Larvae generally settle when they are about 0.9 mm long
and have 11 segments and 4 pairs of elytra.
Flora and Fairbanks, 1966
Kozloff, 1987, 1996
General Notes and
Observations: Locations, abundances,
Authors and Editors
Salish Sea Invertebrates web site provided courtesy of Walla