What are the function for choanocytes in sponges?

Choanocytes, or collar cells, are specialized cells found in sponges that play a crucial role in their feeding and water circulation. They possess a flagellum surrounded by a collar of microvilli, which helps to create a water current through the sponge's body. As water flows past the choanocytes, they trap and phagocytize food particles, such as bacteria and organic debris, allowing the sponge to obtain nutrients. Additionally, choanocytes contribute to the overall circulation of water, aiding in gas exchange and waste removal.