About Eudistylia polymorpha (Johnson, 1901)
Eudistylia polymorpha is a tube-dwelling worm that can reach up to 25 cm (10 in) in length and 1.2 cm (0.5 in) in thickness. The tube it lives in is parchment-like, made of sediment bound together with mucus. It is brownish and translucent, and is often reinforced with sand and shell fragments. On rocky shores, this worm is often hidden in crevices and is hard to dislodge. The feathery crown of this worm is made up of feeding appendages called branchiae, also known as radioles, which also work as gills. These appendages are red or brown, with paler banded sections. Their colouration varies, but the most common pattern is maroon with orange tips. The radioles grow from two spiral, deeply cleft bases. They have eyespots that detect sudden shadows or nearby movement, allowing the crown to retract rapidly into the tube when danger is present. The posterior segments of the worm have hooked bristles that help anchor it inside its tube. E. polymorpha can be told apart from the very similar Eudistylia vancoveri by the cleft in its crown. Additionally, E. vancoveri generally has red branchiae with white tips. The range of E. polymorpha runs along the western coast of North America, from Alaska to California. It occurs in the intertidal zone in tide pools, and in the neritic zone at depths up to 420 m. It typically grows in groups, and can be found growing on rocks, reefs, pilings, wharves, and marinas.
