Ageing impacts phenotypic flexibility in an air-acclimated amphibious fish
The ability to tolerate environmental change may decline as fishes age. We tested the hypothesis that ageing influences the scope for phenotypic flexibility in the mangrove rivulus (Kryptolebias marmoratus), an amphibious fish that transitions between two vastly different environments, water and land. We found that older fish (4–6 years old) exhibited marked signs of ageing; older fish were reproductively senescent, had reduced fin regenerative capacity and body condition, and exhibited atrophy of both oxidative and glycolytic muscle fibers relative to younger adult fish (1–2 years old). However, age did not affect routine O2 consumption. We then acclimated adult fish (1–6 years) to water (control) or air for 10 days to assess the scope for phenotypic flexibility in response to terrestrial exposure. In support of our hypothesis, we found that older air-acclimated fish had a diminished scope for gill remodeling relative to younger fish. We also found that older fish exhibited poorer terrestrial locomotor performance relative to younger adult fish, particularly when acclimated to air. Our results indicate that ageing diminishes skeletal muscle integrity and locomotor performance of amphibious fishes, and may, therefore, impair terrestrial foraging ability, predator avoidance, or dispersal across the terrestrial environment. Remarkably, older fish voluntarily left water to a similar degree as younger fish despite the age-related deterioration of traits important for terrestrial life.
KeywordsAmphibious fish Ageing Phenotypic flexibility Gill remodeling Locomotor performance
We thank Mike Davies, Matt Cornish, Nicole Carpenter, and numerous undergraduate volunteers for animal care. We also thank the reviewers for their helpful commentary.
All authors contributed to the conception and design of the study. GSR, PVC, and LT conducted the experiments, analyzed the data, and wrote the draft manuscript. All authors edited the manuscript.
Funding was provided by Natural Sciences and Engineering Research Council of Canada (NSERC) (Grant number 04218) graduate scholarships to G.S.R., P.V.C., and L.T., and an NSERC Discovery Grant to P.A.W.
Compliance with ethical standards
Conflict of interest
The authors declare no competing or financial interests.
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