Potential factors contributing to extreme longevity in the Greenland shark.

The Greenland shark (Somniosus microcephalus) is a deep-sea vertebrate inhabiting the cold waters of the North Atlantic and Arctic Ocean and is renowned for its exceptional longevity, with individuals estimated to live for more than 400 years. It has also been proposed as a candidate species exhibiting negligible senescence. This narrative review synthesizes current knowledge on the biological mechanisms that may contribute to this phenotype. Potential contributing factors include its extreme environment, low metabolic rate and remarkably late sexual maturation, all of which may reduce cumulative physiological stress over time. At the molecular level, recent genomic studies have identified distinctive features, including duplications of DNA repair genes and structural variation in the tumour suppressor protein p53, which are consistent with enhanced genome maintenance, although their functional significance remains to be experimentally validated. Additional mechanisms, such as proteostatic resilience, antioxidant defences and immune adaptations, may further support long-term cellular homeostasis. Collectively, these observations suggest that the Greenland shark possesses biological characteristics that could influence multiple hallmarks of ageing, including genomic stability, proteostasis and intercellular communication. Emerging evidence also indicates resistance to age-related functional decline in systems such as vision and cardiac function. Taken together, these characteristics highlight the Greenland shark as a valuable, yet still underexplored, model for investigating the biology of longevity and resistance to ageing. Further research in this species may provide insights into the mechanisms underlying healthy ageing across vertebrates and generate hypotheses for future translational studies.