Notes on the Poorly-known Marine Peritrichous Ciliate, Zoothamnium plumula Kahl, 1933 (Protozoa: Ciliophora), an Ectocommensal Organism from Cultured Scallops in Qingdao, China

Summary. The living morphology and the infraciliature of a poorly-known marine ectocommensal peritrich ciliate, Zoothamnium plumula Kahl, 1933 (pro Zoothamnium plumosum Perejaslawzewa, 1886) have been investigated based on specimens collected from within the mantle cavity and the shell surface of the cultured scallop, Chlamys farreri, off the coast of Qingdao, China. The Qingdao-population measures about 50-100 x 30-50 µm in vivo and is characterized by having one apically located contractile vacuole, one-layer peristomial collar, slender body shape and alternatively arranged colony branches. The C-shaped macronucleus is horizontally oriented. Number of silverlines between oral area and aboral ciliary wreath, ca 70; between aboral ciliary wreath and scopula, 24-28. Unlike most other congeners, zooids of this species are often enlarged at the distal end of branches.