The orange spot is called the madreporite, or "mother pore" (a pore is an opening). The starfish draws in water through the madreporite to regulate the pressure in its legs and tube feet. The madreporite is like a sieve. It filters out particles as it draws in water. Sometimes the starfish needs to release water from inside its body, too. The madreporite allows water to move both in and out, so the starfish always has just the amount it needs inside its body.