From "The Intertidal Zone." Courtesy of Bullfrog Films
and the National Film Board of Canada.

Sea cucumbers

Sea cucumbers may look like the fruit in your garden, but they're actually animals--related to sea stars, sea urchins, sea lilies and sand dollars.

Most sea cucumber bodies are covered with tube feet, but only the ones located on the bottom of their bodies are developed enough for use. (However, the hairy cucumber is covered with sleder tube feet.) Sea cucumbers use these feet mainly to attach themselves to the bottom, rather than for motion. The tube feet are controlled by changing the water pressure of the animal. By increasing the amount of water, the feet can be extended; and by lessening the amount of water, the tube feet contract--much like how a sea star moves (~1.6M movie).

Surrounding its mouth are ten to thirty modified tube feet. These sweep the surrounding water, capturing bits of food, and are then transferred one by one to its mouth to wipe off the food. Other sea cucumbers, such as Leptosynapta, burrow in the sediment, digesting what is edible, and excreting the rest.

Sea cucumbers breathe as water is pumped through two respiratory trees located on each side of their digestive tract. Some sea cucumbers can eject their digestive system and associated organs when disturbed (or due to overcrowding or foul water) and grow a new set within a few weeks.

They are sometimes host to the pearl fish, which slides backwards into the respiratory openings of sea cucumbers, often limiting itself to an entire lifre spent within a single individual. Together, they form a commensal relationship, with one member as an uninvited guest, causing no harm and gaining a little from the association.

The most common species in New England is the Orange-footed sea cucumber. It can grow to almost a foot in length, although individuals found in tide pools are usually smaller.

(Icon: Food Web Alert)

Sea cucumbers use their tentacles to capture tiny animals (zooplankton). Some sea cucumbers, such as the worm-like Leptosynapta, burrow and ingest detritis present in the sediement. In Asia, dried sea cucumber bodies (called trepang) and their sex organs are considered a delicacy by humans.

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