Department of Biological Sciences, Clemson University, 132 Long Hall, Clemson, SC 29634, USA.
J Exp Biol. 2012 Feb 1;215(Pt 3):435-41. doi: 10.1242/jeb.054460.
Autotomy (voluntary loss of an appendage) is common among diverse groups of vertebrates and invertebrates, and much attention has been given to ecological and developmental aspects of tail autotomy in lizards. Although most studies have focused on the ramifications for the lizard (behavior, biomechanics, energetics, etc.), the tail itself can exhibit interesting behaviors once segregated from the body. For example, recent work highlighted the ability of leopard gecko tails to jump and flip, in addition to being able to swing back and forth. Little is known, however, about the control mechanisms underlying these movements. Using electromyography, we examined the time-varying in vivo motor patterns at four sites (two proximal and two distal) in the tail of the leopard gecko, Eublepharis macularius, following autotomy. Using these data we tested the hypothesis that the disparity in movements results simply from overlapping pattern generators within the tail. We found that burst duration, but not cycle duration, of the rhythmic swings reached a plateau at approximately 150 s following autotomy. This is likely because of physiological changes related to muscle fatigue and ischemia. For flips and jumps, burst and cycle duration exhibited no regular pattern. The coefficient of variation in motor patterns was significantly greater for jumps and flips than for rhythmic swings. This supports the conclusion that the different tail behaviors do not stem from overlapping pattern generators, but that they rely upon independent neural circuits. The signal controlling jumps and flips may be modified by sensory information from the environment. Finally, we found that jumps and flips are initiated using relatively synchronous activity between the two sides of the tail. In contrast, alternating activation of the right and left sides of the tail result in rhythmic swings. The mechanism underlying this change in tail behavior is comparable to locomotor gait changes in vertebrates.
自切（自愿切断附肢）在各种脊椎动物和无脊椎动物中很常见，人们对蜥蜴尾部自切的生态和发育方面给予了很多关注。虽然大多数研究都集中在蜥蜴的后果（行为、生物力学、能量学等）上，但尾巴本身一旦与身体分离就可以表现出有趣的行为。例如，最近的工作强调了豹纹壁虎尾巴跳跃和翻转的能力，除了能够前后摆动。然而，人们对这些运动背后的控制机制知之甚少。我们使用肌电图，在豹纹壁虎 Eublepharis macularius 自切后检查了尾巴四个部位（两个近端和两个远端）的随时间变化的体内运动模式。使用这些数据，我们测试了以下假设：运动差异仅仅是由于尾巴内重叠的模式发生器造成的。我们发现，自切后约 150 秒，节律摆动的爆发持续时间而不是周期持续时间达到了一个平台。这可能是由于与肌肉疲劳和缺血相关的生理变化。对于翻转和跳跃，爆发和周期持续时间没有表现出规则的模式。与节律摆动相比，跳跃和翻转的运动模式的变异系数明显更大。这支持了这样的结论：不同的尾巴行为不是源自重叠的模式发生器，而是依赖于独立的神经回路。控制跳跃和翻转的信号可能会受到环境感觉信息的修改。最后，我们发现跳跃和翻转是通过尾巴两侧相对同步的活动开始的。相比之下，尾巴右侧和左侧的交替激活导致节律摆动。这种尾巴行为变化的机制与脊椎动物的运动步态变化相当。
