What are the five classes of echinoderms

Interesting facts about echinoderms

To those that have existed for 500 million years Echinoderms belong to the five classes of Starfish (Class Asteroidea), sea ​​urchin (Echinoidea), Sea rollers and Sea cucumbers (Class Holothuroidea), Brittle stars (Class Ophiroidea) and Sea lilies andHair or feather stars (Class Crinoidea).

The echinoderms get their name because of the skeletal elements that protrude from the subcutis in the form of spikes, pins or plates or are embedded microscopically in the body wall.

The body shape of echinoderms is very different: some species are star-shaped with five more or less pronounced arms, others are spherical or cylindrical.

About 6,300 species of echinoderms are known worldwide. The echinoderm's habitat is vast, they live in all seas and oceans in the world. There they can be found from the surf zone to the deep sea trenches, in cold and warm water, in sand and rubble, but also in coral reefs, whereby they depend on the high salinity of the water. 18 species of echinoderms live in the Baltic Sea, one of the largest brackish water areas in the world, such as the edible sea urchin, the common starfish, the scaly brittle star and the black sea cucumber.

The echinoderms live between four and 200 years, depending on the species. Sexual maturity occurs after two to three years, although this also depends on the species and the environmental conditions. Reproduction takes place when the eggs and sperm are released into the open water and are fertilized there. Some species of echinoderms practice brood care, in which only the sperm get into the water and fertilize the eggs that are in a brood pouch.

The food intake of the echinoderms consists mostly of sponges, algae, filtered mud and plant parts or plankton. Among the echinoderms there are omnivores and herbivores, which eat mostly at night. However, there are also the so-called permanent or long-term eaters who specialize in brown algae.

The natural enemies of echinoderms include crabs, snails, fish, ring worms, bristle worms and woodlice. But humans are also dangerous for some species.

Echinoderms move either through ambulacral feet and spines or by moving their arms.