[2] Thyone fusus is found in the northeastern Atlantic Ocean and the Mediterranean Sea, its range extending from Norway southwards to Madeira.

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.

[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.