高水温が海産白点虫の宿主寄生期虫体とシスト期虫体の発達に及ぼす影響を調べたところ, 31℃以下では両ステージとも正常に発達した。また, シストを様々な溶存酸素(DO)条件下で培養したところ, 過飽和 DO および低 DO で発達が抑制された。低 DO で培養したシストを DO 飽和条件下に移すと, 再び発達を開始し, 感染幼虫を放出した。これらの結果から, 白点病が秋季に多発することには躍層崩壊に伴う水底への酸素の供給が関連している可能性が示された。
The Japanese Society of Fish Pathology held a symposium entitled “Current topics on protozoan and other parasitic diseases of fish in Japan” in Miyazaki on 27th September 2001. This symposium was aimed to have an overview of the current status of the researches on protozoan and other parasitic diseases of fish in Japan. Following a keynote presentation of the same subject in the world, two emerging diseases of marine fish in Japan, i.e. emaciation disease in tiger puffer and anemia in Japanese flounder, were introduced. Three species of myxosporeans are responsible for the former disease, and a monogenean Neoheterobothrium hirame causes the latter. The resent researches on kudoosis amami in yellowtail and amberjack, Heterobothrium infection in tiger puffer and blood fluke disease in yellowtail were also presented. The importance of the prevention against the fish protozoan and other parasitic diseases was discussed.