Weinstein R B
Department of Integrative Biology, University of California, Berkeley 94720, USA.
J Exp Biol. 1995 Apr;198(Pt 4):989-99. doi: 10.1242/jeb.198.4.989.
Previous laboratory measurements of the energetics and biomechanics of locomotion have defined performance limits for the ghost crab Ocypode quadrata. To discover whether these animals naturally operate within these limits, a novel infrared videotaping system was used to observe nocturnally active ghost crabs in the field for three-dimensional motion analysis (N = 27) and focal animal sampling (N = 24). Instantaneous movement velocity, movement duration, pause duration and stride frequency were determined from video tapes. Voluntarily active crabs moved at a mean instantaneous velocity of 8 cm s-1. Stressed crabs (i.e. those captured and released into the field site) moved at a mean velocity of 83 cm s-1. The mean movement and pause period durations of voluntarily active animals moving along the beach were 11.2 and 23.4 s, respectively. Stressed crabs had much shorter movement (1.4 s) and pause (7.6 s) durations. Despite the differences in mean movement and pause duration, both voluntarily active and stressed crabs moved for an average of approximately 30% of the observation period. These data indicate that voluntarily active ghost crabs primarily move at velocities that can be sustained aerobically and that their performance is not likely to be altered by moving intermittently. By contrast, stressed crabs move at faster speeds that are closer to the limits of their continuous locomotor performance (e.g. escape behavior and aggressive encounters). In the laboratory, the endurance capacity of crabs moving continuously at these rapid speeds is only a few seconds. However, in the field, the stressed crabs are able to move intermittently for more than a few seconds, yet they do not fatigue. These observations suggest that the performance limits of the stressed crabs are increased by moving intermittently.
先前对幽灵蟹（Ocypode quadrata）运动的能量学和生物力学进行的实验室测量已经确定了其性能极限。为了探究这些动物在自然环境中是否在这些极限范围内活动，研究人员使用了一种新型红外录像系统，在野外观察夜间活动的幽灵蟹，以进行三维运动分析（N = 27）和焦点动物采样（N = 24）。通过录像带确定了瞬时运动速度、运动持续时间、停顿持续时间和步频。主动活动的螃蟹平均瞬时速度为8厘米/秒。受到惊吓的螃蟹（即那些被捕获后又放回野外的螃蟹）平均速度为83厘米/秒。沿着海滩主动活动的动物的平均运动和停顿周期持续时间分别为11.2秒和23.4秒。受到惊吓的螃蟹的运动（1.4秒）和停顿（7.6秒）持续时间要短得多。尽管平均运动和停顿持续时间存在差异，但主动活动的螃蟹和受到惊吓的螃蟹在观察期内平均移动时间约为30%。这些数据表明，主动活动的幽灵蟹主要以有氧方式维持的速度移动，并且它们的表现不太可能因间歇性移动而改变。相比之下，受到惊吓的螃蟹移动速度更快，更接近其连续运动性能的极限（例如逃跑行为和攻击性遭遇）。在实验室中，以这些快速速度持续移动的螃蟹的耐力仅为几秒钟。然而，在野外，受到惊吓的螃蟹能够间歇性移动超过几秒钟，而且不会疲劳。这些观察结果表明，受到惊吓的螃蟹通过间歇性移动提高了其性能极限。
