Comparative analysis of muscle structure and weighted gene co‐expression network analysis reveals growth mechanisms in fast‐growing and slow‐growing silver pomfret ( <i>Pampus argenteus</i> )

Silver pomfret is an important economic fish, and the difference in growth rate is closely related to muscle development. The mechanism of muscle development in fast-growing and slow-growing groups was analysed by skeletal muscle morphology, texture characteristics and gene co-expression network. The results showed that hypertrophy was dominant in the fast-growing group (contribution rate 92.18%), and the muscle fibre diameter and area increased by 3.39 times and 19.94 times, respectively, compared to slow-growing group, whereas hyperplasia was dominant in the slow-growing group (contribution rate 82.11%). The muscle texture properties (elasticity 1.12 ± 0.04, hardness 377.5 ± 2.77, cohesion 0.78 ± 0.01) of the fast-growing group were significantly better than those of the slow-growing group (r = 0.05). Based on Weighted Gene Co-Expression Network Analysis (WGCNA), a total of eight modules were identified to be significantly correlated with growth phenotypes. Among them, the green module (muscle of fast-growing group, R = 0.99) enriched key genes taf1 and med7 and regulated autophagy, p53 signalling pathway and fatty acid metabolism. The key genes of the blue-green module (muscle of slow-growing group, R = 0.89), such as utp6, are involved in MAPK, mTOR pathway and cell cycle regulation. In liver tissues, the pink module (fast-growing muscle liver, R = 0.92) gene was associated with Polycomb inhibition complex, whereas the yellow module (slow-growing muscle liver, R = 0.94) gene was enriched in immune and glucose metabolism pathways. The results showed that the fast-growing group achieved efficient growth through muscle fibre hypertrophy and metabolism-signalling pathway synergism, whereas the slow-growing group relied on hypertrophic and conserved cellular regulatory mechanisms.