Gerald Gary W, Thompson Moriah M, Levine Todd D, Wrinn Kerri M
Biology Department Nebraska Wesleyan University Lincoln NE USA.
Department of Life Sciences Carroll University Waukesha WI USA.
Ecol Evol. 2017 Jul 21;7(17):6729-6735. doi: 10.1002/ece3.3231. eCollection 2017 Sep.
Leg autotomy can be a very effective strategy for escaping a predation attempt in many animals. In spiders, autotomy can be very common (5-40% of individuals can be missing legs) and has been shown to reduce locomotor speeds, which, in turn, can reduce the ability to find food, mates, and suitable habitat. Previous work on spiders has focused mostly on the influence of limb loss on horizontal movements. However, limb loss can have differential effects on locomotion on the nonhorizontal substrates often utilized by many species of spiders. We examined the effects of leg autotomy on maximal speed and kinematics while moving on horizontal, 45° inclines, and vertical (90°) inclines in the cellar spider , a widespread species that is a denizen of both natural and anthropogenic, three-dimensional microhabitats, which frequently exhibits autotomy in nature. Maximal speeds and kinematic variables were measured in all spiders, which were run on all three experimental inclines twice. First, all spiders were run at all inclines prior to autotomization. Second, half of the spiders had one of the front legs removed, while the other half was left intact before all individuals were run a second time on all inclines. Speeds decreased with increasing incline and following autotomy at all inclines. Autotomized spiders exhibited a larger decrease in speed when moving horizontally compared to on inclines. Stride length decreased at 90° but not after autotomy. Stride cycle time and duty factor increased after autotomy, but not when moving uphill. Results show that both incline and leg autotomy reduce speed with differential effects on kinematics with increasing incline reducing stride length, but not stride cycle time or duty factor, and vice versa for leg autotomy. The lack of a significant influence on a kinematic variable could be evidence for partial compensation to mitigate speed reduction.
在许多动物中，腿部自割是逃避捕食尝试的一种非常有效的策略。在蜘蛛中，自割现象非常普遍（5% - 40%的个体可能会缺失腿部），并且已被证明会降低运动速度，进而可能降低寻找食物、配偶和适宜栖息地的能力。先前关于蜘蛛的研究主要集中在肢体缺失对水平移动的影响上。然而，肢体缺失对许多蜘蛛物种经常利用的非水平基质上的运动可能有不同的影响。我们研究了地窖蜘蛛在水平、45°斜坡和垂直（90°）斜坡上移动时腿部自割对最大速度和运动学的影响。地窖蜘蛛是一种广泛分布的物种，栖息于自然和人为的三维微生境中，在自然界中经常出现自割现象。测量了所有蜘蛛在所有三个实验斜坡上移动时的最大速度和运动学变量，所有蜘蛛在每个斜坡上跑两次。首先，所有蜘蛛在自割前在所有斜坡上跑动。其次，一半的蜘蛛被切除一条前腿，另一半保持完整，然后所有个体再次在所有斜坡上跑动。速度随着斜坡角度增加而降低，并且在所有斜坡上自割后也降低。与在斜坡上移动相比，自割后的蜘蛛在水平移动时速度下降幅度更大。步幅在90°时减小，但自割后没有变化。自割后步幅周期时间和占空因数增加，但在上坡移动时没有增加。结果表明，斜坡和腿部自割都会降低速度，且对运动学有不同影响，随着斜坡角度增加步幅减小，但步幅周期时间和占空因数不变，而腿部自割则相反。对运动学变量缺乏显著影响可能是部分补偿以减轻速度降低的证据。
