Choanocyte

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 radial canals in syconoid sponges and form chambers in leuconoid sponges. They bear more than a passing resemblance to Choanoflagellates.

Collar Cells are structures with flagella that help to swish water through the sponge to deliver food and oxygen to its body cells and carry away wastes