Decoding biological aging in Sparus aurata through a gene toolbox to infer welfare assessment and precision...

Biological age (BA) has emerged as a promising integrative indicator of physiological state and welfare, but its use within aquaculture remains underdeveloped. Previous genome-wide analysis in gilthead sea bream revealed skeletal muscle markers with inverse age-related expression and methylation patterns. Specifically, psmd2, ramp1, sirt1 and smad1 were up-regulated and hypomethylated with age, while atp1a2, bmp1, calcrl, col5a1, spred2 and thrb exhibited down-regulation coupled with hypermethylation. Here we assessed the responsiveness of this gene set across multiple aquaculture-relevant challenges using a real-time PCR array. Environmental stressors (e.g. increased temperature and high stocking density with low O₂ concentration) induced transcriptional profiles resembling muscle gene-expression patterns of older individuals. Conversely, cold exposure and nutritional interventions, including restricted feeding and feed supplementation with bioactive protein hydrolysates, microalgae meal with a PUFA-rich lipid source, or fat emulsifiers promoted signatures aligned with those observed in younger animals. Although the direct reversal of stress-induced aging signatures was not tested, results indicate that dietary interventions elicit opposing transcriptional patterns, highlighting potential strategies to mitigate environmentally mediated aquaculture stress through targeted nutrition. These findings provide preliminary evidence of a potential relationship between BA and aquaculture stressors in farmed fish, underpinning a genomics-based framework for welfare assessment and adaptive management.