Description of Zoothamnium
Genus of peritrich ciliates, forming branching colonies. Body elongate conical to almost spherical, posterior with a stalk attaching to the subtsrate, stalk with central contractile spasmoneme, and this also branches such that when one cell contracts in a colony so do many or all other cells in the same colony. Contractile elements may also extend into the base of the body. Peristomial ciliature extends about one full turn at unattached end and leads into buccal cavity. Contractile vacuole(s) empty near base of buccal cavity. Stressed cells produce basal wreath of cilia and can detach from the stalk and swim away. Division leads to the production of a basal telotroch which separates from the parental cell and swims away. Colonies may be quite large.