The function of a choanocyte is to create water flow through the body of a sponge. This allows nutrients to filter through and feed the sponge.
Choanocytes are cells located on the whip-like appendages, called flagella, located in the sponge, reads Reference.com. These flagella then constantly beat at the water, propelling water and nutrients through the pores in the sponge, which the choanocytes trap. The movement of water initiated by the choanocytes aids the digestive and respiratory systems of the sponge, because as well as pulling in water, they also pull in oxygen. They then push out both carbon dioxide and waste materials.
Choanocytes are the third layer that make up a sponge. The first layer gives sponges their pores, and the second layer gives sponges their shape. The cells in the second layer are a mix of mobile and skeletal cells. The mobile cells, called amoebocytes, work in concert with the choanocytes to feed the sponge. They digest the food that the choanocytes provide for them and transport oxygen throughout the body.
The sponge is part of the animal kingdom, but it also shares characteristics with protists, such as the choanocytes. These choanocytes are believed to be a descendant of choanoflagellate, an ancient protist.