Cycliophora
. Symbion, a tiny marine organism so different from any other that it has given rise to a new phylum (see Classification ). Symbion (meaning “living with”) is a commensal, a harmless companion that lives on the mouth hairs of the Norwegian lobster and feeds on the scraps the lobster leaves behind after its messy meals. Symbion's distribution is unknown but may coincide with that of its lobster host. Symbion takes on different forms throughout its strange life cycle. The most common form is the feeding stage, which is about 0.1 mm (0.004 in) long. The body is urn shaped and attached to the lobster by a short stalk and an adhesive disk. On the other end is a funnel-like mouth topped with a ring of microscopic hairs, or cilia. The mouth leads to an S-shaped esophagus, or throat, and a U-shaped digestive system. The first part of the U forms a stomach lined with ciliated and secretory cells; farther along it becomes an intestine, also lined with cilia. Because of the U shape of the dig...