Thyone fusus

Thyone fusus is found in the northeastern Atlantic Ocean and the Mediterranean Sea, its range extending from Norway southwards to Madeira. In the British Isles it is present from the Shetland Isles southwards along the east coast of Scotland to Northumberland. Its depth range is from 10 to 615 m (30 to 2,020 ft). It is found in sheltered positions on shelly and muddy seabeds where it lies buried with just the tentacles and anterior end exposed.^[2]

Thyone fusus is a suspension feeder, consuming diatoms, single-cell algae and drifting organic particles, as well as zooplankton such as copepods, ostracods, protozoans, nematodes, jellyfish and larvae. The two ventral feeding tentacles are much shorter than the others and have forked ends. Each large tentacle in turn shrinks and folds and is pushed into the mouth. A small tentacle is held close to the mouth and cooperates with each of the others by scraping off any food particles that are still adhering to the large one when it is withdrawn from the mouth.^[3]

On the western coast of Ireland, these sea cucumbers bury themselves in the sediment between October and February and go into a form of hibernation. They do not feed during this time and their body wall condition deteriorates, but the gonads continue developing, and spawning takes place in early spring.^[4]