Molecular plasticity to ocean warming and habitat loss in a coral reef fish.

This article investigates how acute thermal stress and habitat complexity independently and interactively affect brain gene expression and oxidative stress in the sergeant major damselfish (Abudefduf saxatilis), a widespread coral reef fish of the Western Atlantic. Juvenile fish were exposed for 10 days to combinations of control (27 °C) or elevated (31 °C) temperatures and complex or simplified habitat structures, revealing that warming significantly increased oxidative damage in the liver and altered brain gene expression related to neurotransmission, immunity, and tissue repair. Although habitat complexity alone did not cause significant gene expression changes, fish in simplified habitats exhibited a greater number of differentially expressed genes under warming, suggesting synergistic effects that impact neural plasticity and spatial memory. The study also presents the first reference transcriptome for A. saxatilis, providing a molecular resource for future research on coral reef fish responses to environmental change. These findings highlight the physiological and molecular plasticity of a generalist reef fish facing combined stressors of climate warming and habitat degradation.