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The Seashore

Sea Cucumbers (Holothurians)

Sea Cucumbers (Holothurians)

Asilia leferevrei with 10 tree-like tentacles. It uses these to suspension feed. Detritus sticks to little hairs on them and then the tentacles are moved to the mouth. Separate sexes with external fertilisation. Asilia can grow to 15 centimetres plus and live for up to 10 years.

General information: There are a number of different species of sea cucumber. Most, particularly the larger species, live off shore but small species can be encountered in the lower shore, living under stones. These tend to be pale in colour and usually white, growing to around 15 cm. Most are only a few centimeres long. Underneath the body are several rows of tube feet used in locomotion. The body is like a long tube but shows bilateral symmetry. At the mouth end of the body is a circle of modified tube feet which are like tentacles which can be withdrawn into the body.

Pawsonia.saxicola and Ocnus lacteus are quite small; the former is very smooth and almost pure white and is known as the Sea-gherkin! The tentacles are dark.

Unlike the other Echinoderms they have a mouth and anus at opposite ends of the tubular, bilateral body. They are worm like but quite muscular. There are no spines on the body and the tube feet are limited to the underside for locomotion. The actual movement is achieved by contractions of the muscular body, the feet acting as a way of attaching to the substrate. Overall, they display little activity and are slow, sluggish creatures. They feed on detritus and small organisms, picked up with the modified feet around the mouth. The food becomes caught in mucous which streams around these "tentacles" and then enters the mouth. When attacked by predators they tend to "explode" their guts in the face of the enemy! The rupturing of the gut and respiratory system is quickly repaired.

 

 


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