Sea cucumbers are marine creatures which are so called because of their elongated body resemblesthe edible plant of the same name. There are well over one thousand species worldwide, and all have thick skin, no visible sensory organs and limited ability to move.
Neopentadactyla mixta, the gravel sea cucumber, is the most common variety in British waters, and is found mostly along the western coast of Britain and Ireland. As the name suggests this sea cucumber lives on heavy sand, gravel or shingle seabeds, in water down to around one hundred metres deep. It has a the typical elongated body of most sea cucumber species, usually 10 to 15cm in length, with small feet running along the body, and a protrusion of tentacles, known as a crown, which extend from one end. This species is usually white or light grey in colour. The sea cucumber buries its body into the sediment and then leaves its tentacles exposed. It relies on living in areas where there is fairly strong tidal flow and feeds by catching organic matter in its tentacles as it flows pasts. Once the tentacle has caught enough food it is withdrawn into the body of the creature where the food is removed and digested. In some areas gravel sea cucumbers can be found in great numbers. Sea cucumbers go into some form of hibernation in winter when the whole body and tentacles are withdrawn into the gravel and they do not feed for some months. The pattern and reason for this hibernation is poorly understood.