Long-term thermal stress reshapes the tolerance of head kidney of Hong Kong catfish (Clarias fuscus) to acute heat shock by regulating energy metabolism and immune response

Elevated water temperatures caused by climate warming can affect fish survival. However, fish can maintain normal physiological functions through physiological plasticity. When temperature fluctuations exceed their tolerance range, even stress-resistant species like Siluriformes are affected. It is known that fish have adaptive regulation mechanisms to reshape their tolerance to temperature stress, but the ability to respond to acute thermal shock and recover after adaptive remodeling remains unclear. This study investigated the effects of different culture temperatures on the ability of Hong Kong catfish (Clarias fuscus) to respond to acute heat stress and stress recovery. C. fuscus were cultured at normal temperature (NT, 26 °C) or high temperature (HT, 34 °C) for 90 days, and then their head kidney transcriptome was analyzed after acute heat stress (34 °C) and subsequent recovery (26 °C). The results revealed 8165 differentially expressed genes (DEGs) in the NT group and 8537 DEGs in the HT group during the entire temperature treatment process, with each group responding differently to various stages of temperature treatment. Enrichment analysis showed that both NT and HT groups had enriched pathways related to energy metabolism and immune response during acute heat stress. However, acute heat stress disrupted the energy supply and oxidative metabolism in the NT group, while enhancing the HT group's ability to respond to repeated heat stress. This experiment demonstrated that high-temperature culture reshaped the energy metabolism balance in the head kidney tissue, improving anti-stress and stress recovery abilities. These findings lay a foundation for further research on the plasticity of fish in coping with acute temperature changes.