Following our experiments in 1962 on the fluctuation of the paralytic toxicity produced in the shellfish (Chlamys nipponensis Akazara Kuroda), we carried out last year same experiments on the shelifish caught in the Bay of Ofunato as those in 1962 and investigated as to whether non-toxic shellfishes of the same species transplanted from a remote and indifferent sea areas, Shizu, to the Bay in question produced any paralytic poison or not.
Results obtained through our studies are as follows:
(1) The shellfish caught in the Bay in question during the rough period from the end of March till the same of May, 1963 was remarkably toxic to mice, following the preceding year, 1962, which showed the same high toxicity in the shellfish as that in the year, 1961, when the paralytic shellfish poisoning broke out, Moreover the toxicity was approximately ten times as strong to mice as that in 1962, and its peak appeared at the end of May.
(2) It was made clear that the sea-water temperature during the poison increasing period in 1963 was lower by about 4° than usual as compared with the temperature 10-14° recorded at the Bay for the past two years and reported by Sommer et al. in U.S.A.
(3) With the transplantation of the non-toxic shellfish from the Bay of Yamada to the Bay of Ofunato, we could recognize no fact that the shellfish had come to contain some toxic substance. It was presumed to be partly because the time of the transplantation was due to the poison-decreasing period in the Bay.