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Recent work has shown that the dorsal fins in fish operate not only as locomotive appendages, but also as sensory structures that aid in proprioception. To investigate how fish use these structures for sensing, the innervation of the dorsal fins in bluegill sunfish (Lepomis macrochirus) was assessed through immunohistochemistry assays. I conducted staining using anti-acetylated tubulin (AAT), a non-specific neuron marker, calcitonin-gene related peptide (CGRP) which stains sensory neurons and cytokeratin 20 (CK20), which binds to mechanoreceptor structures. Stained samples of bluegill dorsal fins were imaged under a laser scanning epifluorescence microscope to visualize mechanoreceptors, as well as sensory and motor neurons. I was able to localize mechanoreceptors in both spiny and soft dorsal fins. Fluorescence imaging revealed ubiquitous sensory innervation throughout the dorsal fins. Putative motor structures tend to be located near the fin base. In the soft dorsal fin, mechanosensory structures were found closer to the fin membrane. Visualization of sensory pathway integration in different regions of the bluegill dorsal fin can further our understanding of how the sensory and motor innervation of fins contribute to overall stability and locomotive capabilities of fish in turbulent environments. Greater knowledge of sensory pathways in simpler appendages like fish fins can provide insight into neuromuscular systems in human limbs and serve as bioinspiration to prosthetics and wearable devices.

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