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

Abstract The traditional culture method of Hyriopsis cumingii is in urgent need of transformation, industrial aquaculture is a sustainable cultivation mode, and the control of environmental conditions and food is the basis and key. To evaluate combined effects of rations (high-ration, medium-ration, and low-ration) and temperatures (13 ± 0.2℃, 23 ± 0.2℃ and 33 ± 0.2℃) on digestion and metabolism of H. cumingii, a 3 × 3 factor comprehensive test was established. Levels of digestive enzymes like amylase (AMS), lipase (LPS), cellulase (CL), metabolic enzymes like glutamic pyruvate transaminase (GPT), glutamic oxaloacetate transaminase (GOT), pyruvate kinase (PK), hexokinase (HK), and metabolism-related genes like carnitine palmitoyltransferase-1 (CPT1), low-density lipoprotein receptor (LDLR) of mussels were analyzed during 21 days. Results showed levels of digestive and metabolic indicators remained stable in the medium-ration × 23℃ treatment, and were significantly (P < 0.05) higher than others on day 21. When exposed to low-ration, high-ration, 13℃ or 33℃, these biochemical indicators rose briefly and then significantly (P < 0.05) declined. Results suggested the medium-ration and 23℃ were the best diet quantity and temperature for H. cumingii. Short-term thermal, cold, semi-starving, and overfeeding treatments induced metabolic levels of mussels to meet the energy demand of anti-oxidative stress. However, long-term stress resulted in liver injury of H. cumingii, reduced the digestive and metabolic efficiency of the mussel, and affected its growth performance and health. This study has practical significance in exploring culture environment and feeding conditions, controlling breeding cost, and increasing the growth and yield in industrial aquaculture.