Thelepus crispus Johnson 1901

How to Distinguish from Similar Species: Other terebellids do not have three pairs of unbranched gills or, if they do, the rows of uncini are not curved to form an ellipse. Amphitrite cirrata is another spaghetti worms but it builds a membranous tube that is not encrusted with sand and shells, and has two interlocking, zipperlike rows of neurosetae.

Biology/Natural History: Terebellids build thin, membranous, sand-encrusted tubes in soft mud and sand. They extend their feeding tentacles from the entrance of the tube like spaghetti over the surface of the nearby sediment. The tentacles are extended out from the burrow by ciliary creeping and they can be retraced by muscular action. Mucus and ciliary action on the feeding tentacles transports small organic particles from the sediment to the mouth, especially along a groove along one side. Mucus and ciliary action on the feeding tentacles transports small organic particles from the sediment to the mouth. The tube of Thelepus crispus is usually made of fragments of shell, stone, and other detritus, is nearly 1 cm wide, and is cemented to the undersurface of or between rocks. It may leave its tube when disturbed and later build a new one. They circulate water through their burrows. The major phosphagen in these worms is phosphoarginine; phosphotaurocyamine is also present. Commensals include the polychaete scaleworms Halosydna brevisetosa and Hololepidella tuta. There are several genera of terebellids that are difficult to tell apart in the field. The feeding tentacles of Thelepus has threadlike, unbranched tentacles, and gills of similar length. Neoamphitrite and Terebella have dark, branching tentacles, which are longer than the gills which are white. Neoamphitrite has 17 thoracic segments while Terebella has 23 to 28. Members of Family Terebellidae have special pumping vessels at the base of the gills to actively pump blood through them.

In sandy mud among stones. Most common terebellid in the rocky intertidal, where it attaches its shell and sand-encrusted membranous tube to the underside of rocks, or between rocks.

Geographical Range: Alaska to S. California; India

Depth Range: Middle to low intertidal

As with all terebellids, this species is benthic, few if any of the segments are longer than wide, the dorsal surface has no paleae, elytra, or felt, it has no cross-barred capillary setae, it has several long, threadlike, extensile, unbranched filamentlike tentacles closely associated with the mouth and are used in feeding but cannot be retracted into the mouth, the notosetae do not form transverse rows that extend nearly to the dorsal midline, the prostomium does not extend posteriorly as an elongated caruncle, and does not have a distinct caudal region which lacks setae, nor form an operculum. Terebellids have soft, light-colored pads on the ventral surface of all or most thoracic segments; these secrete the mucus which builds the tube. The anterior, "thoracic" portion of the body is often larger than the posterior portion. Thelepus crispus has no proboscislike extension to the peristomium, a single row of uncini in the thoracic region which, beginning with segment 8, is curved to form a nearly closed ellipse, 3 pair of slender, unbranched gills, and its capillarynotosetae begin on the 2nd or 3rd gill-bearing segment.