Muscle fiber growth in olive flounder, Paralichthys olivaceus: Fiber hyperplasia at a specific body weight period and continuous hypertrophy

The objective of this study was to investigate muscle fiber growth-related attributes, especially fiber hyperplasia and hypertrophy, and their relation to growth characteristics in olive flounder. After a conditioning period, juvenile olive flounder (214 g of initial body weight) were weighed after 0, 4, 8, 12, and 24 weeks of a feeding trial and were selected based on mean body weight at each period (G1, G2, G3, G4, and G5, respectively). During the 3.0-fold increase in body weight (363.1–1,071 g, p < 0.001), the fiber area was increased approximately 2.2 times (p < 0.05), and the median area increased from the G1 to G5 groups (p < 0.05). The G3 group exhibited a greater fiber number than the G2 group (p < 0.05) as the G3 group exhibited a higher percentage of smaller fiber and mosaic hyperplasia. In addition, a higher percentage of centered nuclei and deoxyribonucleic acid amount in the G2 group were accompanied by an increase in fiber number in the G3 group. Therefore, the muscle growth of olive flounder was influenced by continued fiber area growth and a significant number increase by mosaic hyperplasia during a specific period (G2 to G3 groups; from 512.7 to 670.3 g).