PARALYTIC SHELLFISH POISON-I

1. A series of paralytic shellfish poisoning occurred from eating "akazara-gai", a kind of scallop (Chlamys sp.) in Ofunato City, Iwate Prefecture from May 18 to 20, 1961, in which 20 persons including one death developed symptoms. The epidemiological data indicated that the outbreak was quite similar, to that reported in foreign countries. 2. The highest toxicity in "akazara-gai" and also in mussel was detected in the mid-gut gland and the toxicity in the former shellfish was more than doubled the latter. 3. A marked difference in the toxicity was seen in the shellfish collected in a period from May 20 to July 1, 1961, the sample collected on June 1, about 2 weeks after the outbreak, being the highest. 4. Almost no appreciable decrease in toxicity was observed when a crude poison was heated in Sörensen's phosphate buffer of pH 7.0 at 80°C. for 60 minutes; about 50% was destroyed at 100°C. for 30 minutes, and completely destroyed by autoclaving at 120°C. for 20 minutes. 5. A marked change in the phytoplankton flora was noted when the shellfish became poisonous. Especially, the number and species of diatoms decreased extremely, a dinoflagellate, Peridinium sp. becoming predominant. However, the true source of poison remained to be solved.