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 (Pimelodus pictus), 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 a...机械感觉（mechanosensation）是四足动物（tetrapod）四肢诸多功能的核心基础，但作为四肢同源器官的鱼类成对鳍，相关研究却长期未得到充分探索。本研究旨在探讨：在鳍条未发生大幅度运动的前提下，膜状鳍是否可作为被动结构参与触觉感知。本研究以斑点油鲶（Pimelodus pictus）为实验对象，该物种终生依附底栖基质栖息，且其胸鳍紧邻腹部边缘分布。运动学分析结果显示，该鱼在日常正向游动过程中，胸鳍始终维持部分前伸的恒定角度，且未产生推进力。免疫组织化学检测表明，鳍组织拥有高密度的神经支配，我们在神经纤维末梢处观测到了疑似机械感受器结构。为验证鳍感知机械扰动的能力，本研究针对触碰与弯曲刺激，记录了鳍条神经纤维的电活动。压力刺激与轻度表面刷触均可引发……