White Sea Cucumber (Eupentacta quinquesemita)
The White Sea Cucumber is a common species in rocky areas in the middle intertidal zone and below. Up to about 10 cm in length when relaxed, it is easily recognized by its whitish color and long oral tentacles. The animal is often partially hidden in a crevice with only the feeding apparatus sticking out.
Sea cucumbers are deposit feeders or, in the case of this species, suspension feeders. They extend ten long, much-branched tentacles from the oral end and apply them to the substrate or wave them around in the water, trapping fine particles with mucus. The tentacles are then pushed into the mouth, where mucus and food particles are removed and swallowed. Two of the tentacles are smaller and are used for cleaning the larger ones.
Sea cucumbers vary from their echinoderm relatives in being drawn out in the oral-aboral axis, as if a tomato (sea urchin shape) had been drawn out into a cucumber. The mouth is at one end of the tubelike shape, the anus at the other, making it much like many higher animals. However, inside it retains the radial symmetry of its relatives. The body has five lines of tube feet running along it, the tubes long enough to make the animal look quite fuzzy or prickly. Pieces of the environment are often stuck to the tube feet, perhaps effecting camouflage.
Sea cucumbers perform a behavior that is always startling to the human observer. When disturbed by a potential predator, they may eviscerate their tentacles and foregut into the water. This may startle and confuse the predator as well. However, there is also a seasonal component, and many White Sea Cucumbers in this area routinely eviscerate in the fall, even if not disturbed. The lost parts grow back within a few weeks.
Sea stars of several species are the major predators of these and other sea cucumbers.
White Sea Cucumbers spawn in spring. The sexes are separate, and a large female can release over 100,000 tiny green eggs. After hatching, they go through several rather different-looking larval stages before settling out of the plankton as tiny cucumbers (perhaps should be called “sea pickles”).