Madreporite

Madreporite is a light-colored calcareous opening used to filter water into the water vascular system of echinoderms. It is visible on the aboral surface of the sea star and other echinoderms. The madreporite is connected to a series of canals, the stone canal, which help in the movement of the echinoderm by providing hydraulic pressure to the tube feet.

Structure

The madreporite is a porous, often conspicuous, sieve-like ossicle on the aboral surface of the body of many, but not all, echinoderms. It is connected to the water vascular system via a single stone canal, which leads to the ring canal that encircles the mouth or esophagus. The madreporite, stone canal, and ring canal are parts of the axial complex in the echinoderms.

Function

The madreporite acts as a water filter and supplies the echinoderm's water vascular system with water to move its tube feet. The water vascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. The system is composed of canals connecting numerous tube feet. Echinoderms move by alternating the pressure of the water within the tube feet and the muscular contractions of the tube feet themselves.

In Different Echinoderms

In sea stars, the madreporite is clearly visible on the aboral (upper) surface. In sea urchins, it is located within one of the plates surrounding the anus. In sea cucumbers, it is located in one of the interambulacral areas. In brittle stars, it is located on the oral surface.

See Also

• Echinoderm
• Water Vascular System
• Tube Feet