2025 Volume 91 Issue 1 Pages 28-37
A total of 270 individuals of pufferfish Takifugu flavipterus collected from nine prefectures in Japan were divided into various parts in a thawed frozen, frozen, or fresh fish state, and their toxicity was determined using a mouse bioassay. The results showed that the toxicity of this species was generally very high, with ‘extremely toxic’ (≥1000 mouse units (MU)/g) samples occurring in the skin, liver, ovary, and testis. The toxicity of muscle was ‘nontoxic’ (<10 MU/g) or ‘weakly toxic’ (10–100 MU/g) in frozen or fresh fish, but ‘strongly toxic’ (100–1000 MU/g) samples appeared in thawed frozen fish. A comparison of skin and muscle toxicity among the collection areas indicated that T. flavipterus from Nagasaki, Yamaguchi, Kyoto, Kanagawa, and Tokyo were generally highly toxic, whereas those from Ishikawa, Ehime, Chiba, and Ibaraki were less toxic. Experimental verification of the effect of freezing and thawing on muscle toxicity using 30 T. flavipterus individuals showed that freezing alone had little effect, but thawing elutes the toxin from toxic parts, especially the skin, and some of the toxins are transferred to the muscle. If the toxicity of the skin is high, the toxin can penetrate the center of the muscle.
