Characterization of transcriptomic profiles underlying gross morphological changes observed in semelparous pink salmon (Oncorhynchus gorbuscha)

Immune and inflammatory processes were elevated in skeletal muscle and head kidney, while gonads showed strong enrichment of insulin signaling, steroid metabolism, and hormone-response pathways. Analysis of endocrine receptor expression identified tissue-specific and ohnolog-specific regulation of receptors involved in thyroid, growth hormone, insulin, gonadotropin, sex steroid, and glucocorticoid signaling, suggesting functional divergence among duplicated salmonid genes.

These findings identified in pink salmon provide evidence that the demonstrate that the most extreme physiological changes occur extensive molecular reprogramming in pink salmon occurs duringat the time of final maturation rather than freshwater entry. The coordinated activation of endocrine, metabolic, and degenerative pathways supports a mechanistic link between reproductive development and semelparous senescence, providing new insight into the endocrine and transcriptomic networks that govern spawning-associated physiological decline in Pacific salmon.