The mangrove rivulus (Kryptolebias marmoratus) is a phenotypically plastic teleost fish that can spend considerable time on land and traverse the terrestrial realm through a ballistic behavior termed the tail-flip jump. The tail-flip jump is a transitional stage between fully aquatic and terrestrial lifestyles. Therefore, understanding this behavior can provide insight into how organisms adapt to new environments over evolutionary time. Taxa that are successful tail-flip jumpers have a deep caudal peduncle and uniform body shape. Studies of K. marmoratus show that terrestrial acclimation and exercise improves tail-flip jumping performance due to muscle remodeling, but the implications of these muscular changes on aquatic locomotion are unknown. In the present study, we hypothesized that 1) terrestrial acclimation and exercise lead to physiological and anatomical changes to optimize tail-flip jump distance and endurance while negatively impacting swimming performance in K. marmoratus, 2) terrestrial exercise causes muscle redistribution toward the posterior of K. marmoratus to better facilitate the tail-flip jump, and 3) terrestrial exercise and air exposure cause behavioral changes in K. marmoratus, made possible by the large degree of neural and behavioral plasticity displayed by this species. To test these hypotheses, we measured the critical swimming speed (Ucrit), tail-flip jump distance, terrestrial endurance, mass distribution along the anterior-posterior axis, and undisturbed aquatic behavior of age- and size-matched K. marmoratus before and after a terrestrial exercise period. This period consisted of six three-minute exercise sessions spread over 12 days, during which the fish were prompted to jump continuously. To isolate the effects of air exposure, a separate group was exposed to air for an equivalent period but not allowed to jump. Air exposure improved maximum jump distance and negatively affected swimming performance (Ucrit). Terrestrial endurance (number of jumps) improved in the exercised group, but Ucrit did not change. Contrary to our first hypothesis, a trade-off exists between jump distance and Ucrit, but not between jump endurance and Ucrit. No change to body mass distribution was detected. Exercised individuals were more active following exercise, resulting either from onset of a dispersion behavior or a heightened stress response.
Date of Degree
Master of Science (MS)
Science, Engineering and Technology
Axlid, E. (2022). Functional trade-offs between terrestrial and aquatic locomotion in the amphibious fish Kryptolebias marmoratus [Master’s thesis, Minnesota State University, Mankato]. Cornerstone: A Collection of Scholarly and Creative Works for Minnesota State University, Mankato. https://cornerstone.lib.mnsu.edu/etds/1220/
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