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

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.