103.1 Saturday, Jan. 7 Pectoral fins as sensors: Spatial distribution of sensory input to the pectoral fins of the bluegill sunfish. HALE, M. E. *; WILLIAMS IV, R.; Univ. of Chicago email@example.com
Pectoral fins function in many behavioral contexts for fishes including in locomotion, feeding and social interactions. In some unusual species, such as the gurnards, the pectoral fin rays are adapted to act as sensors, probing the sea floor for prey. The role of less specialized pectoral fin rays in mechanosensation has not been explored in depth. We have found extensive sensory innervation of the pectoral fins in more typical ray-finned fishes including bluegills and zebrafish. Fin rays and membranes are invested with nerve fibers that run nearly parallel to the rays, branching along their lengths with the rays. Endings of these afferent nerve fibers are positioned along the proximodistal axis of the rays and concentrated at the leading edge and distal tips of the fin. In the bluegill, we have demonstrated that populations of afferent nerve fibers fire during fin ray bending. A fundamental question about fin ray mechanosensation is how sensory nerve fiber input contributes to spatial resolution along the proximodistal axis of the rays. We investigate the spatial organization of fin ray mechanosensation by regionally bending fin rays and determining the physiological response through extracellular recordings of fin ray nerves. We use spike-sorting algorithms to tease apart the firing of neuron populations projecting to distal and proximal regions of the ray. Our data indicate that bending is sensed at multiple locations along the fin ray and that the input from points along the ray is likely independent, suggesting that the fish may discern the location where bending is occurring along the length of the fin ray. Mechanosensation may be a fundamental role of the pectoral fins and should be considered in studies of fin function and evolution.