Strikingly noticeable PSP-infested specimens of the scallp Patinopecten yessoensis were examined for anatomical distribution of the toxicity. The unfrozen adductor muscle showed toxicity scores as low as 3-13 MU/g, even when the shellfish was toxified up to unprecedented levels of 6, 500-11, 000 MU/g difestive gland. With the specimens of toxicity levels ranging from 1, 000-2, 900 MU/g digestive gland, the adductor muscle, either washed or non-washed, were nontoxic.
The latter scallops showed a toxicity score less than 2 MU/g non-washed adductor muscle, when kept frozen for five months and thawed quickly by heating at 100°C for 5 min, or thawed less quicky by leaving at room temperature (17-21°C) for 4 h. Their toxicity levels were 3-9 MU/g adductor muscle when thawed slowly by leaving at 5°C for 24 h.
On the other hand, the toxicity of adductor muscle was raised up to 54 MU/g, when the freezing-thawing of the whole shellfish was repeated three times, indicating the migration of toxin from one tissue to another.