Muscle fibre type composition in the lateral muscle of olive flounder Paralichthys olivaceus

In this paper, a combined-method study has been made on the lateral muscle of the teleost olive flounder Paralichthys olivaceus in just-hatched and adult stages. In just-hatched stage, both slow and fast muscle fibres were detected: (1) in situ hybridization analysis indicated that slow and fast myosin heavy chain genes were specifically expressed in the superficial and deep part of the myotomal muscle, respectively; (2) immunohistochemistry analysis showed that fibres in the deep part reacted with anti-fast myosin antibody F310; (3) western blot analysis detected a weak expression of slow myosin and a strong expression of fast myosin. In adult stage, the slow and fast muscle fibres had their own distribution characteristics: (1) hematoxylin/eosin staining showed the histological characteristics of the muscle fibre composition; (2) histochemical observations showed that the deep muscle fibres, and some fibres near the epidermis, contain alkali-stable myofibrillar ATPase activity; (3) immunohistochemistry analysis indicated that all the deep muscle fibres reacted with F310 antibody and some fibres in the superficial layer of muscle also reacted with F310; (4) western blot analysis showed that fast myosin was expressed both in the blended muscles (the mix of superficial and deep muscles) and deep muscles, while slow myosin was mainly expressed in the blended muscles. These findings suggested that both slow and fast muscle fibres existed in the musculature of the olive flounder in just-hatched and adult stages. Notably, the adult fast fibres also exist in the superficial layer of the muscle.