In two different places on the starfish respiration or gas exchange happens. One of the places is through the skin on the ends of the tube feet. Gas exchange can occur in the dermal gills or papulae. These gills are lined with cilia that move to produce a current. When the thin skin of the tube feet takes in the oxygen out of the water and through the tube feet the carbon dioxide exits. To do that starfish have to depend on osmosis, which is the process of particles moving across a membrane to gather oxygen from the surrounding water and dispel carbon dioxide. The hole on the top of their bodies is called a madreporite. Water is collected through the madreporite and fills the coelom and the coelom is criss-crossed by many body canals. Those
