Geographic and seasonal distribution of the infective stage of Ceratomyxa shasta (Myxozoa) in Northern California

The geographic distribution of the infective stage of Ceratomyxa shasta (in California, USA) is limited to the San Joaquin, Sacramento, Pit, and Klamath river systems. In the San Joaquin system, the infective stage occurs in the Mokelumne River. In the Sacramento system, the infective stage occurs in the mainstem of the Sacramento k v e r as well as in some major tributaries (Feather River, Butte Creek). In the Klamath system, only the mainstem of the Klamath River is infective. The occurrence of infective C. shasta in the Klamath River is seasonal. During 1986-1987, the river was infective until December 5 to 15 (water temperature 7 "C). The river was non-infective until spring of 1987. Infectivity reoccurred on April 9 to 20 (water temperature 15 "C).