1Graduate School of Science and Technology, Nagasaki University, Nagasaki 852-8521, 2Faculty of Fisheries, Nagasaki University, Nagasaki 852-8521, 3Nagasaki Municipal Fisheries Center, Nagasaki 851-0014, 4Nagasaki Fishing Port Fisheries Processing Plant Complex Cooperative Society, Nagasaki 851-2206, 5Japan Frozen Foods Inspection Corporation, Minato, Tokyo 105-0012, Japan
A total of 5 feeding experiments were conducted, in which non-toxic cultured puffer fish ‘torafugu’ Takifugu rubripes were reared for 60 days with various types of tetrodotoxin (TTX)-containing diets. The test fish administered with a crude extract from toxic tissues of a wild puffer ‘nashifugu’ T. vermicularis accumulated a small amount of TTX (less than 3 MU/g in most cases) mainly in the skin and liver at low dose (0.1 MU/(1 g body weight·day)), and a large amount (up to 57 MU/g) mostly in the liver and ovary at higher doses (0.2-1.0 MU/(1 g body weight·day)). The accumulation rate of toxin in 0-year-old fish reared in aquaria was calculated to be 0-17%, whereas that in 1-year-old fish reared in netcages to be more than 30%. The toxin, once accumulated in the puffer tissues, was retained there for at least 45 days without any toxic diet being supplied. When a purified sample of TTX (95% purity) was administered, the puffer accumulated it up to similar levels as in the crude toxin. The fish were also found to accumulate generally high concentrations of toxin if directly fed with minced tissues of T. vermicularis.