Reef-Forming Sponge (Heterochone calyx)
The reef-forming sponge is a member of the class Hexactinellida, in which the sponges have six rays on each spicule and are made of silica (the same material that makes up glass). The reef-forming sponge can grow very big. For example, off Canada's British Columbian coast, reef-forming sponges grow to sizes up to 65 feet long. Like its cousins in Calcarea and Demospongiae, hexactinellid sponges have specialized cells called collar cells rather than organs that draw water into the sponge's body to be filtered for food and to exit through large openings called osculae.