Cave Adaptation Favors Aging Resilience in the Mexican Tetra

All animals age, but the rate at which some species age varies widely. What environmental pressures and what molecular factors underlie the remarkable diversity in aging and lifespan across species remains largely enigmatic. The Mexican tetra, Astyanax mexicanus , serves as an intriguing new model to study how adaptations to different environments can change aging. This species exists as two morphotypes: the river-dwelling surface fish, which inhabits environments rich in food and light, and the blind cave-adapted cavefish, that thrive in dark, nutrient-limited but predator free environments. Nutrient limitation and lack of predation are known to impact lifespan, however, how adaption to such environments changes the aging trajectory in this species remains unknown. Here, we compared aging markers between surface and cavefish populations, focusing on morphological and behavioral changes, as well as molecular signatures, and found that aging markers are pronounced and evident in surface fish, whereas these signatures are less distinct in aged cavefish. Using zebrafish, we explored the contribution of the cavefish insulin receptor mutation to longevity. Although the insulin receptor mutation is sufficient to increase lifespan in fish, our findings suggest its impact is limited. Instead, our data indicate that metabolic shifts, particularly those related to mitochondrial function, may be key contributors to the extended longevity observed in cavefish.