Sea Cucumbers are characterized by their cylindrical shape. Their mouth is located on the front part of the body, and the anus on the rear portion of the body. They have five paired rows of water-filled tube feet on the lower portion of their body. In the region of their mouth the feet have turned into tentacles, and these arms branch out and can contract using long muscular action. Their bodies are soft and lengthened, the size of the Sea Cucumber is anywhere between 3 cm. to one meter, depending on their sex. They live on the sandy sea bed and crawl along using their podia, or by contracting their body muscles.
Their main food is the decaying organic matter found in the sediment, and which they gather using their tentacles.
Some species are nourished from the mold in sand. They pass large quantities of sand through their mouths into their digestive systems, so they can take advantage of the organic materials in it. The discharge is removed through their anus in the form of cylindrical sand. The Sea Cucumbers breathe in a unique way, and this occurs through muscle contractions that create a kind of pumping action.
In most of the species, the genders are separate. In many of the species the sex cells are released into the water and that is how fertilization takes place. During fertilization, certain of the species raise the front portion of their body above the sea-bed and discharge their sex cells into the water; spawning occurs simultaneously for that entire population. The larvae are equipped with organs of motion and can swim with the plankton. This stage lasts for a number of weeks and continues with the deposit of the young on the sea-bed until they develop into adult form. Many types cover themselves with grains of sand, small stones and fragments of coral for camouflage. Some types are equipped with a special defense mechanism, and when endangered, they discharge white or pink threads from their anus. These threads are sticky and the attacker becomes entangled in them. Sometimes these threads will contain a toxic substance that repels other creatures.
Despite the fact that the body covering of the Sea Cucumber is flexible, they are able to harden themselves if there is any threat of being attacked. For some species, the method of defense is different and unusual: when they are threatened they are able to turn their body inside-out, so that their intestines are on the outside. One of the possible explanations for this strange behavior is that the Sea Cucumber can deliberately sacrifice its intestine to the predator that is threatening it, so that the predator will be satisfied and leave. The intestine itself can regenerate.
There is a fish parasite called the “pearlfish” which makes its home in the respiratory system of the Sea Cucumber; at night these fish leave the body of the Sea Cucumber through the anus, and hide there again whenever danger is present.
Did you know that?
Sea Cucumbers breathe through their anus.