Starfish belong to the tribe of the “echinoderms” – their relatives are the sea urchins. They can be found in many seas, most of them are found near the coast.
They take in their food, which consists of snails or mussels, through a mouth opening facing downwards. This is a rather complicated process because food is often taken directly through the stomach by being put over the prey through the mouth opening. The actual digestion then takes place outside the animal, after which the stomach is pulled back into the body.
Not all starfish have five arms; there are also species that have more. On the arms, there are “feet” that are used to move. There are also small suction cups on the feet.
Starfish do not have a brain, but they do have a nervous system. With this, stimuli that are received via sensory cells are processed. At the tips of the arms, starfish have light-sensing cells.
The exoskeleton is made of lime and is arranged in small “platelets” that are movable but connected to one another. Reproduction takes place via eggs that are fertilized in the water. First larvae that swim around freely develop from the eggs.
Source: https://en.wikipedia.org/wiki/Starfish