Abstract
Kudoa megacapsula was found in the somatic muscle of yellowtail Seriola quinqueradiata, which were raised from wild seedlings (juveniles) imported from South Korea. Numerous parasitic foci, 2-3 mm in size, were recognized as filamentous ‘black cysts’ in the skeletal muscle, while no muscle liquefaction was observed. The spores (34.6 × 28.9 μm in mean size) were cruciform to stellate and had four distinct winglike projections, in which one extremely large and three small polar capsules were present. These morphological characteristics and small subunit ribosomal DNA sequences of the myxozoan were consistent with those of K. megacapsula, which was originally described from red barracuda Sphyraena pinguis caught off the coast of China. Histopathological observation revealed that plasmodia developed intracellularly within the myofibrils, followed by encapsulation by host's fibroblast layers, resulting in granulomatous inflammation.
