Amphibious fish ‘get a jump’ on terrestrial locomotor performance after exercise training on land

Many amphibious fishes rely on terrestrial locomotion to accomplish essential daily tasks, but it is unknown whether terrestrial exercise improves the locomotor performance of fishes on land. Thus, we tested the hypothesis that terrestrial exercise improves locomotion in amphibious fishes out of water as a result of skeletal muscle remodeling. We compared the jumping performance of Kryptolebias marmoratus before and after an exercise training regimen, and assessed the muscle phenotype of control and exercise-trained fish. We found that exercise- trained fish jumped 41% farther and 48% more times before reaching exhaustion. Furthermore, exercise training resulted in the hypertrophy of red muscle fibers, and an increase in red muscle capillarity and aerobic capacity. Lactate accumulation after jumping indicates that white muscle is also important in powering terrestrial jumps.Overall, skeletal muscle in K. marmoratus is highly responsive to terrestrial exercise, and muscle plasticity may assist in the effective exploitation of terrestrial habitats by amphibious fishes.

诸多两栖鱼类依靠陆地运动完成日常必需活动，但目前尚不明确陆地运动是否能够提升鱼类在陆地的运动表现。为此，我们验证了如下假说：两栖鱼类离开水体后的陆地运动表现提升，源于骨骼肌重塑。我们比较了斑纹隐小鳉（Kryptolebias marmoratus）在运动训练方案实施前后的跳跃性能，并评估了对照组与运动训练组鱼类的肌肉表型。实验结果显示，运动训练组鱼类的跳跃距离提升了41%，力竭前的跳跃次数增加了48%。此外，运动训练可引发红肌纤维肥大，同时提升红肌的毛细血管密度与有氧代谢能力。跳跃后的乳酸积累现象表明，白肌在为陆地跳跃供能方面同样发挥着关键作用。综上，斑纹隐小鳉的骨骼肌对陆地运动具有高度响应性，而肌肉可塑性或可助力两栖鱼类有效开拓陆地生境。