Urechis unicinctus

Ecology

This spoonworm is a detritivore, feeding on detritus and lives and burrows in sand and mud like other Urechis species. It creates a U-shaped burrow in the soft sediment of the seabed. A ring of glands at the front of the proboscis secrete mucus which sticks to the burrow wall. The worm continues to exude mucus as it moves backwards in the burrow thus creating a mucus net. The worm draws water through its burrow by peristaltic contractions of its body and food particles adhere to the net. When enough food is gathered, the worm moves forward in its burrow and swallows the net and entangled food. This process is repeated, and in an area with plenty of detritus, may be completed in only a few minutes.

Large numbers have been known to become stranded on beaches in Japan; the original theory was that they were beached due to sea storms, but scientists have theorized that they swim at night to reproduce, which would raise the chances of beachings.