Starfish are echinoderms. Echinoderms are invertebrates, most of which are benthic and can move slowly, and are distributed from shallow sea to deep sea. In addition to starfish, common echinoderms include sea urchins, sea cucumbers, sea snake tails, etc. Their structures are quite different. Its feeding methods are mainly swallowing, filter feeding and meat feeding, and its reproduction is mainly oviparous, and it is also necessary to reproduce asexually. But also has strong regeneration ability.

1. Shellfish: Most starfish feed on shellfish. Starfish have long wrists that can be bent, and there are many suckers. With these, starfish can absorb the two sides of shellfish, so that the meat inside can be exposed, and then digested with digestive enzymes, and then swallowed it.

2. Crustaceans: Some starfish don't have too long wrists, or they don't have suckers on their wrists, so they can't prey on shellfish and can only eat smaller crustaceans. When eating, it will swallow the whole food, and then slowly digest the food in its stomach.

3. Microorganisms: There are also some starfish living in the deep sea, which rarely catch shellfish and crustaceans. They mainly feed by cilia filtration, and sweep the sediment organic matter falling into the body surface into the step belt groove by cilia to form a food rope, which is then sent into the mouth.