Biology (Basel) 2026 Jun 11;1512:. doi: 10.3390/biology15120913.

Thermal Stress Disrupts Gut Microbiota, Induces Oxidative DNA Damage, and Modulates Immune and Stress-Related Gene Expression in the Red Sea Urchin (Loxechinus albus).

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The red sea urchin Loxechinus albus is a species of high commercial importance in Chilean aquaculture, whose performance is strongly influenced by environmental conditions such as temperature. The gut microbiota plays a central role in host physiology; however, its interaction with stress-induced molecular responses remains poorly understood. This study evaluated the effects of thermal stress on food consumption, gut microbial composition, oxidative status, and immune- and stress-related gene expressions in L. albus gut. Sea urchins were exposed to control (16 °C) and elevated temperature (22 °C) conditions for 7 and 14 days. Gut microbiota was characterized using 16S rRNA sequencing, while oxidative damage to DNA and proteins was quantified. Gene expression analyses targeted markers of apoptosis (casp3, casp10, bak1), cellular growth (mtor, raptor), stress response (hsp70), and immune regulation (nfκb, foxo). Thermal stress induced a marked reduction in microbial alpha diversity and promoted a shift toward opportunistic taxa. Heat-stressed individuals exhibited significantly increased oxidative DNA damage, whereas protein oxidation remained unchanged. Gene expression analyses revealed early upregulation of casp3, casp10, nfκb, foxo, and hsp70, suggesting activation of apoptotic, immune, and stress-response pathways. In contrast, bak1, mtor, and raptor showed limited or no significant modulation. These findings demonstrate that thermal stress disrupts host-microbiota homeostasis and induces oxidative and molecular responses in L. albus. This integrative response provides insight into mechanisms underlying physiological performance under thermal stress, with important implications for aquaculture sustainability.

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