Microscopic and ultrastructural characteristics of Kudoa infection in a butterfly fish (Chaetodon).

Myxosporidiosis of the skeletal muscle was diagnosed in a pearl scale butterfly fish (Chaetodon). On the basis of light and electron microscopy, the infectious agent was thought to be a Kudoa. The muscle had fusiform cysts containing myxosporidian organisms within hypertrophied fibers. Ultrastructural features of the kudoa organisms were four external shell valves joined by sutural planes. Internally, four pyriform polar capsules with polar filaments were anterior to the sporoplasm.