A NEW GENUS OF ANAEROBIC SCUTICOCILIATE WITH ENDOSYMBIOTIC METHANOGENS AND ECTOBIOTIC BACTERIA

Isocyclidium globosum n.gen. n.sp. is a freshwater anaerobic scuticoci liate with endosymbiotic methanogens and ectobiotic bacteria. It has b een retrieved from anoxic water and sediments in Spain and England. Th e ciliate has mitochondria-like microbodies: these form a continuous s heet, lying immediately beneath the cell membrane in the posterior hal f of the ciliate. The endosymbiotic methanogens lie next to the microb odies. Rod-shaped bacteria attached to the external surface of the cil iate were observed only when the ciliate was obtained from sulphate-ri ch anoxic water. We describe the morphology, infraciliature and ultras tructure of the ciliate and its associated symbionts and other bacteri a.