Objective Ambient temperature changes, particularly cooling, can induce metabolic disorders in fish, resulting in a substantial accumulation of free radicals. This, in turn, affects the normal physiological functions and immune defense mechanisms of fish cells and tissues. This study aimed to investigate the stress response of fish to abrupt temperature changes.

Methods Mastacembelus armatus was used as the experimental model. The study simulated the stress response of fish under temperature fluctuations by implementing a temperature change protocol (initial temperature group: 28 °C→low-temperature maintenance group: 20 °C→recovery temperature group: 28 °C). The effects of these temperature fluctuations on antioxidant indices and heat shock protein gene expression were assessed.

Results The activities of superoxide dismutase (SOD) and catalase (CAT) in the liver of M. armatus significantly decreased during temperature fluctuations (P<0.05). Total antioxidant capacity (T-AOC) increased in the low-temperature maintenance group, but no significant difference were observed among the three groups (P>0.05). Malondialdehyde (MDA) levels significantly increased in the low-temperature maintenance group (P<0.05), but returned to initial levels in the recovery temperature group. Compared to the initial temperature group, the expression level of hsp60 in gill tissue was significantly reduced in the low-temperature maintenance group and increased significantly in the recovery temperature group (P<0.05). The expression of hsc70 in gill tissue showed a significant downward trend in the low-temperature maintenance group (P<0.05); however, in brain tissue, the expression of hsc70 in the recovery temperature group was significantly lower compared to the low-temperature maintenance group (P<0.05). The expression of hsp70 in gills and brain tissue significantly decreased in the low-temperature maintenance group and significantly increased in the recovery temperature group (P<0.05). Conversely, the expression of hsp90 in both gills and brain tissues significantly increased in both the low-temperature maintenance and recovery temperature groups (P<0.05).

Conclusion This study demonstrates that rapid temperature fluctuations in aquatic environments can induce oxidative stress responses and affect the expression of heat shock protein genes in different tissues of M. armatus.

Significance The findings provide valuable data and theoretical insights for ecological domestication, healthy breeding practices, environmental management, and value-added maintenance of M. armatus.