Kirkton Scott D, Niska Jared A, Harrison Jon F
Section of Organismal, Integrative, and Systems Biology, School of Life Sciences, Arizona State University, PO Box 874601, Tempe, AZ 85287-4501, USA.
J Exp Biol. 2005 Aug;208(Pt 15):3003-12. doi: 10.1242/jeb.01747.
Developing vertebrates increase both their locomotory power output and endurance due to ontogenetic improvements in anaerobic and aerobic metabolic capacities. Do similar patterns hold for insect locomotion, or do longer tracheal lengths create problems for oxygen delivery in older animals? We forced developing American locust grasshoppers (Schistocerca americana) to jump repeatedly and examined the effect of development on power output, endurance, lactate concentration, oxygen consumption and the oxygen sensitivity of jump performance. As previously shown, power outputs, relative leg lengths and leg cuticular content increased with age. A key finding of this study is that both lactate concentration and aerobic metabolic rate of the jumping muscle increase with age, explaining how the increased leg cuticular stiffness can result in increased power output. After two minutes of jumping, grasshoppers rely completely on aerobic ATP production. The rise in mass-specific, active aerobic metabolic rates with age indicates that problems with longer tracheae can be overcome; however, the reduced endurance, higher lactate concentrations and increased oxygen sensitivity of locomotory performance in older animals indicate that larger/older grasshoppers have smaller safety margins for oxygen delivery during hopping.
由于无氧和有氧代谢能力的个体发育改善，发育中的脊椎动物会增加其运动功率输出和耐力。昆虫的运动是否也有类似模式，或者更长的气管长度是否会给老龄动物的氧气输送带来问题？我们迫使发育中的美洲沙漠蝗（Schistocerca americana）反复跳跃，并研究发育对功率输出、耐力、乳酸浓度、耗氧量以及跳跃性能的氧敏感性的影响。如先前所示，功率输出、相对腿长和腿部表皮含量随年龄增加。本研究的一个关键发现是，跳跃肌肉的乳酸浓度和有氧代谢率均随年龄增加，这解释了腿部表皮硬度增加如何导致功率输出增加。跳跃两分钟后，蝗虫完全依赖有氧ATP产生。随着年龄增长，质量特异性的活跃有氧代谢率升高表明，较长气管带来的问题可以被克服；然而，老龄动物耐力降低、乳酸浓度升高以及运动性能的氧敏感性增加表明，较大/较老的蝗虫在跳跃过程中氧气输送的安全边际较小。
