Echinoderm is a kind of invertebrate living in shallow water. The main feature is that the body is spherical, disc-shaped or heart-shaped, without wrists. The endoskeleton heals with each other to form a strong shell. Most species have a complex chewing device in their mouths, called Aristotle's lantern, which has teeth and can chew food.
The digestive tube is tubular and coiled in the body, feeding on algae, corals and worms. Polymorphism, the individual develops through sea urchin larvae (long wrists), and then metamorphoses into juvenile sea urchins, reaching the need of sexual maturity 1-2 years. It can be divided into regular sea urchins and irregular sea urchins, with a total of 22 orders. There are more than 900 species belonging to 225 genera. There are about 100 known species and 7,000 fossil species in China.
Living habits
Born timid, he runs as long as he sees the enemy, but the sea urchin doesn't move fast. Most sea urchins live on the bottom of the sea, and they like to live in reef forests or crevices in the sea below the intertidal zone rich in algae, as well as in the hard sandy muddy shallow sea zone, which has the characteristics of avoiding light and coming out at night.
Sea urchins will move with food intake: if there is enough food, they can move more than 1 meter every day; If food is scarce, sea urchins may only move 10 cm every day. The movement of sea urchins is accomplished by transparent, small, numerous and sticky tube feet and spines.
The tube foot moves like a starfish, which can catch rocks, while the spines at the bottom hold up the sea urchin's body and help it move at will. When they move, they can always take the direction of the walking belt as the guide without turning their heads. When the sea urchin is turned over, its thorns and tube feet can make it turn over to the right.