The consistency of madreporite is calcerous. Madreporite has openings like a sponge to filter out water from its system.

Water enters the starfish through the madreporite or the tube feet, but mainly the madreporite.

It is located on the Aboral surface of the starfish (upper side), and it is sightly off centered, however not to be confused with the anus, the Madreporite is slightly larger than the anus.

mouth, madreporite, suckers

The madreporite on a sea star acts like a pressure equalizing valve and is used to filter water. It is located on the surface of the central disk. It is a small yellow or red, button-like structure, looking like a small wart.