Kinematic data Indiv1 from Channel catfish use higher coordination to capture prey than to swallow

When animals move they must coordinate motion among multiple parts of the musculoskeletal system. Different behaviours exhibit different patterns of coordination, however, it remains unclear what general principles determine the coordination pattern for a particular behaviour. One hypothesis is that speed determines coordination patterns as a result of differences in voluntary versus involuntary control. An alternative hypothesis is that the nature of the behavioural task determines patterns of coordination. Suction-feeding fishes have highly kinetic skulls and must coordinate the motions of over a dozen skeletal elements to draw fluid and prey into the mouth. We used a dataset of intracranial motions at five cranial joints in channel catfish (<i>Ictalurus punctatus</i>), collected using X-ray reconstruction of moving morphology, to test whether speed or task best-explained patterns of coordination. We found that motions were significantly more coordinated (by 20–29%) during prey capture than during prey transport, supporting the hypothesis that the nature of the task determines coordination patterns. We found no significant difference in coordination between low- and high-speed motions. We speculate that capture is more coordinated to create a single fluid flow into the mouth while transport is less coordinated so that the cranial elements can independently generate multiple flows to reposition prey. Our results demonstrate the benefits of both higher and lower coordination in animal behaviours and the potential of motion analysis to elucidate motor tasks.

动物运动时，必须协调肌肉骨骼系统多个部位的动作。不同行为表现出不同的协调模式，但目前仍未明确决定特定行为协调模式的通用原则。一种假说认为，由于自主控制与非自主控制存在差异，速度决定协调模式；另一种假说则提出，行为任务的本质才是协调模式的决定因素。吸食摄食（suction-feeding）鱼类拥有高度活动性的头骨，需要协调十余块骨骼结构的运动，才能将流体与猎物吸入口腔。我们采用通过运动形态学X射线重建（X-ray reconstruction of moving morphology）采集的斑真鮰（Ictalurus punctatus，即斑鲶）颅内5处颅骨关节的运动数据集，检验速度与任务究竟哪一项更能解释协调模式的差异。研究结果显示，猎物捕获阶段的运动协调性较猎物转运阶段显著提升20%~29%，这一发现支持任务本质决定协调模式的假说。我们未观察到低速与高速运动间的协调性存在显著差异。我们推测，捕获阶段协调性更高，是为了形成单一的流体流入口腔；而转运阶段协调性更低，则可让颅骨结构独立产生多股流体，以重新定位猎物。本研究结果证实了高低两种协调性在动物行为中的各自优势，同时也彰显了运动分析在阐明运动任务机制方面的应用潜力。