A starfish is also known as a sea star because of its star-like shape and its five legs. In fact, sea star is a more appropriate name because this marine animal isn't a fish. It has no backbone, making it an invertebrate, while fish have backbones, making them vertebrates. A starfish also has no gills, scales or fins, which are normally found in fish.
The starfish has spiny skin covered in pincers and suckers that allow it to move. It has little spots on the tips of its arms that serve as eyes. These spots are sensitive to light and enable it to forage for food. The starfish feeds primarily on clams, oysters and snails. The starfish attaches itself to a clam and then pushes its stomach out through its mouth toward its prey. The enzymes in the stomach slowly digest the soft part of the clam, and the digested materials enter the stomach.
The starfish not only lives in the ocean but in tidal pools, sea grass, rocky shores, sand, kelp beds and coral reefs as well. There are nearly 2,000 different species of starfish. Although many starfish species have five arms, there are some varieties with many more than this, such as the sun star with its 40 arms.