Bryozoan skeletons grow in a variety of shapes and patterns: mound-shaped, lacy fans, branching twigs, and even corkscrew-shaped. Their skeletons have many tiny openings. Each opening is the home of "zooid". They have a body with a U-shaped gut, opening at the mouth and at the anus. They feed with their lophophore. The tentacles of the bryozoans are ciliated. The beating of the cilia creates a current of water which drives food (mainly phytoplankton) towards the mouth. In some groups, notably some ctenostomes, a gizzard may be formed. 