Abstract
Rising ocean temperatures disrupt neuroendocrine–immune interactions in vertebrates. Neuroendocrine gene expression in the liver, spleen, intestine, blood cells and epigonal organ was examined in small‐spotted catsharks ( Scyliorhinus canicula ) exposed to a 30‐day simulated marine heatwave. Correlations among neuroendocrine genes, immune‐ and iron‐related genes, plasma biochemistry and leukocyte assays revealed tissue‐specific expression patterns, reduced inter‐individual variability and coordinated transcriptional modulation across tissues. Overall, catsharks exhibited integrated adjustments to thermal stress, most likely to balance metabolic demands with immune resilience.