Development of Ceratomyxa shasta (2005-FP-10) FWS Agreement No.: 813336G008 Submitted by:

ii Ceratomyxa shasta is a serious pathogen of anadromous salmonids in the Klamath River Basin. It has a complicated life history using salmonids as the vertebrate host and the freshwater polychaete Manayunkia speciosa as the invertebrate (definitive) host. The objectives of this study were to: (1) rear Manayunkia speciosa in the laboratory so that its life history could be described, (2) examine uninfected and infected polychaetes histologically so that histopathology of infection could be described, and (3) describe the sequential development of C. shasta in the polychaete. This final report is broken into three parts which correspond both to these objectives and to three papers submitted or to be submitted to peer-reviewed journals. Part 1 includes rearing and life history of the polychaete. Part 2 includes internal anatomy and histology of the polychaete. Part 3 includes sequential development of C. shasta in M. speciosa with notes on the histopathology. ii