The freshwater polychaete Manayunkia speciosa serves as the obligate intermediate host for the myxosporean parasites Ceratomyxa shasta and Parvicapsula minibicornis, which adversely affect the survival and freshwater production of juvenile salmon in the Klamath River and elsewhere in the Pacific Northwest USA. Scant information on the life history of the polychaete and inability to maintain individuals in culture has hindered development of management strategies to control disease outbreaks in Klamath River salmon. Through trial-and error- manipulations of food and water sources, culture environments and water velocities, we established conditions that allowed us to maintain M. speciosa in culture over a 10-mo period. In lab culture, eggs and young were brooded within the maternal tube for a 6–8 wk period during which 5 developmental stages were distinguished. Peak egg production occurred in late spring-early summer, with each female brooding up to 35 offspring. Juveniles left the maternal tube at a length of approximately 1 mm, and became reproductively mature in late December to early January at a length of approximately 2 mm. Duration of survival in lab culture, coupled with the absence of adult polychaetes in preserved river samples that were collected in mid-summer, suggests that M. speciosa has an approximately annual generation time.