

They are sometimes called Hexactinellida. Glass sponges use silicon dioxide to make their skeletons.Of the about 15,000 sponges known, about 400 are Calcarea. They are usually very small, only 3-4 inches in height. Bony sponges use calcium carbonate to make the skeleton.The sponges in this class make their skeleton from spongin.


Animals that get food this way are called filter feeders. Most sponges filter (take out) little bits of food from the water going through their bodies. The water goes out through a big tube in the center. All sponges take in water through pores (little holes) in their bodies. There are more than 10,000 species of sponge. Most of them feed on bacteria and other microorganisms. Their bodies are full of pores and channels allowing water to circulate through them. The basic body plan is a jelly-like layer sandwiched between two thin layers of cells. Nevertheless, sponges are quite successful. A sponge is an animal that grows in one spot like most plants do. It is sessile: it cannot move from place to place the way most animals can. It is a simple animal with many cells, but no mouth, muscles, heart or brain. A sponge is a member of the phylum Porifera.
