Data from: Touch sensation by pectoral fins of the catfish Pimelodus pictus

Mechanosensation is fundamental to many tetrapod limb functions yet it remains largely uninvestigated in the paired fins of fishes, the limb homologs. Here we examine whether membranous fins may function as passive structures for touch sensation in the absence of extensive fin ray movement. We investigate the pectoral fins of the pictus catfish (<i>Pimelodus pictus</i>), a species that lives in close association with the benthic substrate and whose fins are positioned near its ventral margin. Kinematic analysis shows that the pectoral fins are held at a constant angle of partial protraction during routine forward swimming and do not appear to generate propulsive force. Immunohistochemistry reveals that the fins are highly innervated and we observe putative mechanoreceptors at nerve fibre endings. To test for the ability to sense mechanical perturbations, activity of fin ray nerve fibres was recorded in response to touch and bend stimulation. Both pressure and light surface brushing generated afferent nerve activity. Fin ray nerves also respond to bending of the rays. These data demonstrate for the first time that membranous fins can function as passive mechanosensors and suggest that touch sensitive fins may be widespread in fishes that maintain a close association with the bottom substrate.

机械感觉是众多四足动物肢体功能的核心基础，但作为肢体同源结构的鱼类成对鳍，其相关研究迄今仍相对匮乏。本研究旨在探究：在鳍条未发生大幅运动的情况下，膜质鳍是否可作为被动触觉感知结构发挥作用。我们以纹猫鲇（<i>Pimelodus pictus</i>）为研究对象，该物种常紧密依附底栖基质生存，其成对鳍恰好位于腹缘附近。运动学分析显示，纹猫鲇在常规向前游泳时，胸鳍始终维持在部分展开的恒定角度，且似乎不产生推进力。免疫组织化学检测结果表明，该鱼类的鳍拥有高密度神经支配，我们还在神经纤维末梢处观测到疑似机械感受器的结构。为验证鳍的机械感知能力，我们记录了鳍条神经纤维在受到触碰与弯曲刺激时的电活动。无论是施加压力还是轻度表面刷拭，均可诱发传入神经活动。鳍条神经同样会对鳍条的弯曲产生响应。本研究首次证实膜质鳍可作为被动机械感受器发挥功能，同时提示：与底栖基质紧密共生的鱼类中，具有触觉感知能力的鳍可能广泛存在。