Graduate Thesis Or Dissertation

Occurrence of the protozoan fish parasite Ceratomyxa shasta in the Deschutes River basin and the ultrastructure of the spore

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  • The purpose of this paper was twofold, (1) to determine the distribution of the infective stage of Ceratomyxa shasta (Noble) in the Deschutes River basin, and (2) to study the ultrastructure of the spore stage of the protozoan parasite. Liveboxes containing juvenile rainbow trout were placed at specific test points in the Deschutes River system. After an exposure period, the fish were examined for the presence of the parasite. C. shasta was detected in this manner in each of the three main tributaries to the Deschutes River. In the Metolius River the source of infection was Suttle Lake. In the upper Deschutes River the source was Crescent Lake. Crooked River was thought to contain the infective stage of C. shasta in the lower reaches because of contamination with Deschutes River water entering by irrigation canals. Odell and Davis Lakes (not directly connected to the Deschutes River) contain the infective stage, but are thought to constitute a closed system. The ultrastructure of the spore of C. shasta was examined by electron microscopy. Penetration of embedding plastic into the spore was possible only when the specimens were placed in 10% formalin for an extended period of time. The valves of the spore form knobs at the suture line similar to those of other myxosporidians. A septate desmosome similar to that described in Hydra (Wood, 1959) was identified between the two valves. Within the sporoplasm are two vesicular nuclei with nucleoli, endoplasmic reticulum, electron dense circular bodies, mitochondria and ribosome. packets. The polar capsule and filament of C. shasta are morphologically similar to those of other myxosporidians.
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