Starfish are animals that live on the sea floor. They got their name from their shape: They look like stars with at least five arms. If a component is bitten off, it will grow back. In case of danger, they can also tie off an arm themselves.
In biology, the starfish form a class from the echinoderm phylum. There are about 1600 different species. They differ in size, ranging from a few centimeters to one meter. Many have five arms, but there can be as many as fifty. Some species grow new arms throughout their lives.
Most starfish have spines on the top. They have little feet underneath that they use to move around. Suction cups can also be included. They like to attach themselves to the panes of an aquarium, for example.
People catch starfish to eat or decorate their homes with. They are also used as fodder for poultry. Various Indians and the ancient Egyptians used them as fertilizer for their fields. However, starfish are not endangered.
How do starfish live?
Almost all species live in shallow water, where there are ebbs and flows. A few starfish, on the other hand, live in the deep sea. They can live in the tropics, but also in the Arctic and Antarctic. Some can live in brackish water, which is fresh water mixed with salt water.
Some species feed on algae and mud, while others eat carrion or mollusks such as snails or mussels, or even fish. The mouth is on the underside in the middle of the body. Some species can bulge their stomachs. They have enough strength in their little feet to push the mussel shells apart. They then partially digest their prey first and only then draw it into their own bodies. Other species swallow their prey whole.
Starfish have no heart and therefore no blood and no circulatory system. Only water moves through her body. They also have no head and no brain. But many nerves run through her body. With special cells, they can distinguish between light and dark. Some researchers recognize them as simple eyes.
Starfish reproduce in many different ways. In most cases, the male releases his sperm into the water, and the female releases her eggs. That is where fertilization takes place. The eggs develop into larvae and then starfish. Other egg cells are fertilized in the mother’s womb and feed on her egg yolk there. They hatch as live animals. Still, others develop from a single parent, i.e. asexually.