(zoo-tham-knee-um) is a colonial peritrich ciliate. The feeding cells in sessile peritrich ciliates have lost all of the somatic cilia and only have the feeding cilia. The feeding cilia form a wreath which extends around the front of the cell and descends into a narrowing buccal cavity. This cavity ends at the cytostome where food is packaged into food vacuoles. If the cells become unhappy, they produce a temporary wreath of basal cilia (trochal cilia), break away from their stalk and use these to swim. The contractile elements of all associated cells of Zoothamnium
colonies are interconnected so that if one cell contracts, all will tend to contract together. Differential interference contrast.