Mechanisms of homing in the fiddler crab Uca rapax 2.: Information sources and frame of reference for a path integration system
Mechanisms of homing in the fiddler crab Uca rapax 2.: Information sources and frame of reference for a path integration system
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DOI：
10.1242/jeb.00661
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发表时间：
2003-12-01
影响因子：
2.8
通讯作者：
Duncan, LMJ
中科院分区：
文献类型：
--
作者：
Layne, JE;Barnes, WJP;Duncan, LMJ
招潮蟹 Uca rapax 是中心地带的觅食者，它们的觅食距离可达洞穴数米。这项研究调查了这些螃蟹返回洞穴时使用的方向和距离信息的来源。我们测试了归巢过程中使用的空间参考系（自我中心或外中心）以及空间信息源（自体或异体）。我们还测试了它们整合了运动的哪些组成部分（仅自愿，或自愿加反射）。招潮蟹在其自然泥滩栖息地中，在正常觅食行为期间使用实验者控制的圆盘被动旋转，然后才返回家园。当圆盘转动时，螃蟹通过反向旋转来抵抗圆盘上的被动旋转，这是对意外运动的补偿性反应。螃蟹通常偏心地位于圆盘上，因此当圆盘旋转时也会发生平移。没有螃蟹主动补偿这个翻译。完全补偿圆盘旋转的螃蟹不会产生方向性归航错误。没有完全补偿的螃蟹会沿着反映其新身体方向的方向归巢。换句话说，如果我们成功地重新定向螃蟹（即它对圆盘旋转补偿不足），则无论视电机补偿的大小如何，其归位误差都等于其重新定向的角度。每个计算机模型的螃蟹都配备了一个路径积分器，利用外部（异体）和路径相关（异体）输入的不同组合，遍历真实螃蟹的数字化路径。然后将模型螃蟹计算出的归巢向量与在真实螃蟹中观察到的归巢方向进行比较。采用与真实螃蟹最接近的模型家乡向量来构成招潮蟹所采用的路径整合机制。最符合真实螃蟹的模型获得了独特的方向和距离（来自本体感受器等内部来源），并且仅集成了自愿运动信息。螃蟹还被要求穿过一块潮湿的醋酸盐跑回家，它们在上面滑倒，因此被迫在回家的路上采取比回家向量理论上所需的更多的步骤。穿过这片土地的奔跑速度异常低的螃蟹在找到洞穴之前也会停下来。跑动速度不受路面阻碍的螃蟹并没有短暂停留，而是径直跑向洞穴入口，没有湿滑路面的对照组螃蟹也是如此。我们将此解释为，一些螃蟹的速度因滑倒而受到阻碍，因此在用完归巢向量后，它们在接近洞穴的地方停下来。这是支持路径整合是由腿部本体感受器或传出命令介导的假设的积极证据，但我们的数据不允许我们区分这两种可能性。
Fiddler crabs Uca rapax are central-place foragers, making feeding excursions of up to several meters from their burrows. This study investigates the sources of directional and distance information used by these crabs when returning to their burrows. We tested the spatial frame of reference (egocentric or exocentric), and the source of spatial information (idiothetic or allothetic) used during homing. We also tested which components of their locomotion they integrated (only voluntary, or voluntary plus reflexive).Fiddler crabs in their natural mudflat habitat were passively rotated during normal foraging behavior using experimenter-controlled disks, before they returned home. Crabs resisted passive rotations on the disk by counter-rotating when the disk turned, which was a compensatory response to unintended movement. Crabs were usually situated eccentrically on the disk, and therefore were also subjected to a translation when the disk rotated. No crab actively compensated for this translation. Crabs that fully compensated for disk rotation made no directional homing error. Crabs that did not fully compensate homed in a direction that reflected their new body orientation. In other words, if we succeeded in reorienting a crab (i.e. it undercompensated for disk rotation), its homing error was equal to the angle by which it had been reoriented, regardless of the magnitude of the optomotor compensation.Computer-modelled crabs, each equipped with a path integrator utilizing different combinations of external (allothetic) and path-related (idiothetic) input, traversed the digitized paths of the real crabs. The home vector computed by the model crab was then compared to the homing direction observed in the real crab. The model home vector that most closely matched that of the real crab was taken to comprise the path integration mechanism employed by fiddler crabs. The model that best matched the real crab gained direction and distance idiothetically (from internal sources such as proprioceptors), and integrated only voluntary locomotory information.Crabs were also made to run home across a patch of wet acetate, on which they slipped and were thus forced to take more steps on the homeward path than theoretically required by the home vector. Crabs whose running velocity across the patch was unusually low also stopped short of their burrow before finding it. Crabs whose running velocity was not impeded by the patch did not stop short, but ran straight to the burrow entrance, as did control crabs that ran home with no slippery patch. We interpret this to mean that the velocity of some crabs was impeded because of slipping, and these therefore stopped short of their burrow after having run out their homing vector. This is positive evidence in support of the hypothesis that path integration is mediated either by leg proprioceptors or by efferent commands, but our data do not allow us to distinguish between these two possibilities.