Lugworm Arenicola marina
One of the most familiar sights on western European beaches is the neat, coiled casts of undigested sand deposited by lugworms. The worm itself is rarely seen, remaining hidden in its U-shaped tube beneath the surface of the sand. The entrance to the tube is marked by a shallow, saucer-shaped depression in the sand. The worm may be pink, red, brown, black, or green. The first six segments of its front section are thick with bristles, while the next thirteen segments have red, feathery gills. The rear third of the body is thin, with no gills or bristles.
Lugworms feed by eating sand, extracting organic matter from it, and expelling the waste. These fleshy worms are a favorite food of many wading birds and are also used by fishermen as bait. They are most abundant at mid-shore level in sediments containing reasonable amounts of organic matter.