Sea cucumber - from the name it seems that it is some kind of marine plant, however, in fact, it is a class of invertebrates such as echinoderms. Some of the species used for food bear the more familiar name "trepang".
They are also called holothurians (Latin Holothuroidea). About 1, 100 species of sea egg are known. The name "sea cucumbers" was given to these animals by Pliny, and the description of some species belongs to Aristotle.
The body of the sea cucumber is leathery to the touch, usually rough and wrinkled with well-developed muscle bundles. The longitudinal muscles (5 bands) are attached to the calcareous ring around the esophagus. At one end of the body is the mouth, at the other is the anus. The mouth is surrounded by a corolla of 10-30 tentacles that serve to capture food, and leads into a spirally twisted intestine. In a word, an ordinary overgrown marine worm. Indeed, the body length in most sea cucumbers varies from 0.5 centimeters to 2 meters, and in some species (for example, the spotted synapt) it can reach up to 5 meters.
Another interesting feature of sea cucumbers is their incredible coloration, ranging from brown speckled to bright yellow with orange and blue stripes, which makes them look like giant caterpillars.
These invertebrates can be found in almost all seas except the Caspian and Baltic. They inhabit both coastal areas and deep-sea depressions. Coral reefs serve as their main home.
Holothurians are sedentary or crawling animals; they mainly feed on plankton, small animals, algae and organic debris, collecting them from the bottom together with silt and sand. In the intestines of "cucumbers" nutrients are selected from this mixture, and all unnecessary goes back out. By the way, earthworms feed in the same way in terrestrial ecosystems. An interesting fact is that the sea cucumber is a large slothbone; it always lies on its side during hunting and rest.
When attacked by a predator, galaturia throws out the back of the intestine along with the water lungs through the anus, scaring off or distracting the attackers. In some species, Cuvier tubes containing toxins are also ejected. The discarded organs take the form of long threads, usually white, that envelop the enemy, depriving him of mobility. With the sea cucumber itself, nothing happens; the lost organs, it quickly grows back.
The poisonous properties of sea cucumbers were used in the past by the indigenous inhabitants of some islands of the Pacific Ocean for fishing. So, the natives of the Marshall Islands threw the insides of holothurians into shallow bodies of water, after which the fish stunned by the poison floated to the surface. It is also described that the islanders applied these sticky threads to wounds as a kind of bandage.
Interestingly, sea cucumbers can reproduce both by division and sexually. Females lay eggs directly in the water, and the male fertilizes them. Some species are caring parents. For example, the red sea cucumber, which lives off the coast of California, bears its eggs on its back under the calcareous plates. When ripe, the larvae break through the mother's skin and start free swimming. And during reproduction by division, the body of the sea cucumber is divided into several parts, from which new sea cucumbers then grow.
The life span of this unusual animal is from 5 to 10 years, although many do not live up to this time. Man uses over 30 species and varieties of sea cucumbers for food. Edible sea cucumbers, which are often called trepangs, have long been valued as a very nutritious and healing dish, therefore, the fishing of these animals has been practiced since ancient times.