The architecture of cell differentiation in choanoflagellates and sponge choanocytes SUMMARY: The closest relative to multicellular animals are single-celled organisms called choanoflagellates. These protists look like collar cells. These are cells that have a microvillar ring (the collar) around a flagellum. An example of these cells in animals are sensory epidermal cells. To get a… Continue reading The architecture of cell differentiation in choanoflagellates and sponge choanocytes