A new phylum, discovered by P. Funch and R. M. Kristensen in 1995 in the N. Sea and Kattegat, and so far known by only one species, Symbion pandora, which lives attached to the mouth-parts and appendages of lobsters. S. pandora is less than 1 mm long, acoelomate, bilaterally symmetrical, sac-like, and attaches by an adhesive disc. It has a ring of cilia around the mouth and an anus just outside this ring. Sexes are separate; males are much smaller than females. It can also reproduce asexually, by budding. The adult, feeding stage alternates with a non-feeding, free-swimming, larval stage.
Subjects: Zoology and Animal Sciences.