There are 5,000 to 10,000 species of sponges in the world. Most sponges live in salt water.
Sponges are covered with tiny pores which are called "ostia." Internally, sponges contain a system of "canals" that are lined with cells, which allow sponges to perform life functions (such as breathing, eating and discarding waste).
Sponges are "filter feeders." As water flows through their bodies, sponges will capture and ingest food particles carried by the water.
Sponges capture bacteria, plankton, and other tiny organic particles.
The sticky cells that exist within the inner "canals" of the sponge are called "choanocytes" (or "collar" cells). Food particles carried by flowing water are captured by these collar cells.
Amebocytes are other cells that are found within the sponge's inner canal. They are transporter cells that carry food captured by the collar cells to other cells inside the body of the sponge.