| Abstract: | The histological properties of the cephalad parts of the dorsal ordinary muscles (CD‐OMs) of wild (body weight 33.3 ± 0.9 kg, n = 3) and full‐cycle cultured (body weights 13.1 ± 2.6 (FC 1), 20.2 ± 1.0 (FC 2) and 28.5 ± 3.6 (FC 3) kg, n = 3 respectively) Pacific bluefin tuna were investigated. The CD‐OMs of FC 1–3 tuna showed low moisture content (P < 0.05) and high fat content (about six times more, P < 0.05) in comparison with wild fish. A large quantity of adipose tissue was observed in the wide spaces between muscle fibres in the CD‐OMs of FC 1‐3 tuna. The muscle fibre diameter of the CD‐OM of FC 3 tuna was significantly lower than that of wild fish (P < 0.05). Myofibrils in the CD‐OM of wild tuna were surrounded by a developed sarcoplasmic reticulum and mitochondria; however, there were many glycogen granules among the myofibrils and a large quantity of fat in the CD‐OM of full‐cycle cultured fish. In particular, the glycogen content of the CD‐OM of FC 3 tuna was significantly higher (about 50 times) than that of wild fish. These results indicate that feeding and exercise conditions affect the histological structure and metabolism of the bluefin tuna muscle. Copyright © 2006 Society of Chemical Industry |
