Enzyme activities and gene expression in digestion and metabolism of thetriangle sail mussel Hyriopsis cumingii under different temperature and diet ration

The traditional culture method of Hyriopsis cumingii is in urgent need of transformation. Industrial aquaculture, a sustainable cultivation mode, relies on the control of environmental conditions and food supply. To evaluate combined effects of different rations (high-ration, medium-ration, and low-ration) and temperatures (13.0±0.2), (23.0±0.2) and (33.0±0.2)℃) on digestion and metabolism of H. cumingii, a comprehensive 3 × 3 test factorial experiment was established. Digestive enzymes (e.g., amylase, lipase, cellulase) and metabolic enzymes (e.g., glutamic pyruvate transaminase, glutamic oxaloacetate transaminase, pyruvate kinase, hexokinase) along with metabolism-related genes (e.g., CPT1, LDLR) were assayed over a 21-day period in mussels. The results showed that levels of digestive and metabolic indicators remained stable in the medium-ration×23℃ treatment, and were significantly higher than others on day 21 (P<0.05). When exposed to low or high-ration, as well as 13 or 33℃, these biochemical indicators rose briefly and then significantly declined (P<0.05). Principal component analysis (PCA) demonstrated a clear separation of treatment groups based on digestive and hepatic enzyme activities, with PC1 accounting for 67.73%-80.73% of the total variance. Enzyme activities were notably reduced under extreme temperatures and altered feeding levels, while lipase, amylase, cellulase, and key hepatic metabolic enzymes contributed positively to PC1.These findings suggest that the medium-ration and a temperature of 23℃ were the optimal diet quantity and environmental conditions for H. cumingii. Short-term thermal, cold, semi-starving, and overfeeding treatments induced metabolic levels of mussels to meet the energy demand for anti-oxidative stress. However, long-term stress led to liver injury of H. cumingii, resulting in reduced digestive and metabolic efficiency of the mussel, and subsequently affecting its growth and overall health. This study holds practical significance in exploring culture environment and feeding conditions, controlling breeding cost, and increasing growth and yield in industrial aquaculture.