Enterocytozoon hepatopenaei (EHP) is an important factor limiting the growth of Penaeus vannamei. Its simple transmission route and lack of effective control drugs often lead to great losses for the shrimp aquaculture industry. In this study, some basic information of EHP was provided, including EHP spore purification, germination promoting treatment, quantification determination of the key genes expression, and the activities determination of key enzymes in glycolysis pathway at the stage of spore germination. The result showed that light microscopic and scanning electron microscopic analyses confirmed KOH promoted germination. The expression of the glyceraldehyde 3-phosphate dehydrogenase gene was stable, with high-level expression in treatment groups. Hexokinase gene expression and enzyme activity increased after promoting germination treatment. These findings indicated that the glycolytic pathway is enhanced during EHP germination. The results suggest that we can prevent EHP from invading host cells by attempting to block the energy supply.
Kudoa (Myxosporea: Multivalvulida) parasites are critical pathogens in marine and freshwater fish associated with significant economic losses and reduced market prices caused by post-mortem myoliquefaction or numerous cysts on muscles. In the present study, large yellow croakers infected by Kudoa were found during fish disease surveillance in China in November 2020 and used for morphological observation and characterization using light DIC microscopy and electron microscopy. Numerous creamy-white oval plasmodia were observed in muscles and on the surface of brain cartilage, gill arches, and serosal surfaces. The spores were considerably longer and thicker than previously reported Kudoa, with protruding polar filaments (PFs) in the mature spores, fingertip-shaped apical projections (APs), and polar capsules. Phylogenetic analyses with SSU rDNA, LSU rDNA, and mitochondrial DNA showed that the Kudoa-infected sample (LcK-2020) had the highest similarity to Kudoa iwatai reported in Japan. Based on the morphological characterization and phylogenetic analysis, it could be concluded that the sample LcK-2020 was infected by Kudoa iwatai, which would be the first report of Kudoa iwatai infection in large yellow croaker in China.
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