Page "Madreporite" Paragraph 1

The madreporite () is a lightcolored calcerous opening used to filter water into the water vascular system of echinoderms.

It acts like a pressure-equalizing valve.

It is visible as a small red or yellow button-like structure, looking like a small wart, on the aboral surface of the central disk of a sea star.

Close up, it is visibly structured, resembling a " madrepore " ( stone coral, Scleractinia ) colony.

From this, it derives its name.