Choanocytes (also known as "collar cells") are cells that line the interior of Asconoid sponges that contain a central flagellum surrounded by a collar of microvilli. It is the closest family member to the free-living ancestor called choanoflagellate. The flagellae beat regularly, creating a water flow across the microvilli which can then filter nutrients and other food from the water taken from the collar of the sponge. Food particles are then phagocytosed by the cell. Choanocytes line the radi… (More on Choanocyte)