From ball to cup shape – Choanoflagellates collective behavior
“C. flexa cells form sheets in which all the cells’ flagella point in the same direction—just like epithelial cells, which make up skin and many tissues in animals. King notes that these were probably the first tissues to evolve in animals.
When C. flexa’s sheets curl up into a ball with the flagella pointing outward, the ball swims quickly by waving the tail-like structures. Or the sheet can flip into a cup shape by unfolding and then curling in the opposite direction, in such a way that all the flagella face inside. “In this form, it’s really good at catching bacteria,” King says. Sponges, one of the earliest lineages of animals to evolve, use a similar structure to feed.”