common Star fish (sea stars)
The scientific name for the common star fish is Asterias rubens. There are some 2,000 species of sea star living in all the world’s oceans, from tropical habitats to the cold seafloor. They have bony, calcified skin, which protects them from most predators, and many wear striking colors that camouflage them or scare off potential attackers, and on average live up to 35 years. Purely marine animals, there are no freshwater sea stars. Beyond their distinctive shape, sea stars are famous for their ability to regenerate limbs, and in some cases, entire bodies.
digestive system
The beginning of the process- Starfish have a unique digestive system with a mouth at the center of their underside and an anus on their upper surface. Food can be brought into the stomach through the mouth or, in many species, the cardiac stomach can be extended out through the mouth to digest food outside the body. They then use their tube feet to pass the food to the stomach.
The stomach(s)- Some species use their water vascular system to open the shells of some mollusks and inject their stomachs into the shells. It then digests the mollusk in place. Partially digested food is passed to the inside of the starfish where digestion continues in the pyloric stomach. The sea star's arms are filled with digestive glands called pyloric caeca which help with digestion. These digestive glands secrete enzymes and absorb required vitamins from food.
The end of the process- A small intestine runs from the secondary stomach to the anus which is located in the central upper part of the body.
Here are some good animations to help understand the functions of a starfish
The stomach(s)- Some species use their water vascular system to open the shells of some mollusks and inject their stomachs into the shells. It then digests the mollusk in place. Partially digested food is passed to the inside of the starfish where digestion continues in the pyloric stomach. The sea star's arms are filled with digestive glands called pyloric caeca which help with digestion. These digestive glands secrete enzymes and absorb required vitamins from food.
The end of the process- A small intestine runs from the secondary stomach to the anus which is located in the central upper part of the body.
Here are some good animations to help understand the functions of a starfish