Screening and Identification of the Biomarkers Applied for the Evaluation of Acute and Chronic Thermal Tolerance Ability in Largemouth Bass ().

Affected by the continuously rising temperature, thermal stress leads to a delinked growth rate and resistance to stress in cultured largemouth bass (, LMB) in China. Identification of LMB with better thermal resistance will benefit the breeding of new varieties. However, there has been limited reporting on the evaluation to identify LMB with better thermal resistance. LMB consists of the northern LMB (, NLMB) and the Florida LMB (, FLMB). Due to their different geographical distributions, it has been suggested that FLMB exhibit better thermal resistance compared to NLMB. In this study, NLMB and FLMB were subjected to thermal stress for 3 h (acute) and 60 d (chronic) at 33 °C, respectively. Subsequently, the variations of 12 candidate biomarkers between NLMB and FLMB were analyzed. Exposure to acute thermal stress significantly increased plasma cortisol, blood glucose, and lactate levels; activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), glucose kinase (GK), pyruvate kinase (PK), lactate dehydrogenase (LDH), and glucose 6 phosphatase (G6Pase); and the expressions of and in both NLMB and FLMB ( < 0.05). Compared to NLMB, FLMB exhibited a lower plasma cortisol level and a higher expression of under acute thermal stress ( < 0.05). Exposure to chronic thermal stress significantly increased plasma cortisol and blood glucose levels, as well as activities of GK, PK, LDH, and G6Pase, as well as expressions of and in both NLMB and FLMB ( < 0.05). Additionally, FLMB showed a lower expression of compared to NLMB ( < 0.05). In conclusion, our results showed that LMB with lower plasma cortisol level and higher expression of under acute thermal stress, as well as lower expression of under chronic thermal stress were suggested to have better thermal resistance. Our study provides valuable information for identifying and breeding LMB varieties with better thermal resistance in the future.