Meeting Abstract

P3.157  Sunday, Jan. 6  Sensitive spikes and spines: The pectoral spines of catfish function as touch sensors STEINWORTH, BM*; WILLIAMS IV, R; HALE, ME; University of Chicago; University of Chicago; University of Chicago bsteinworth@uchicago.edu

The first pectoral fin ray of catfish is modified into a sharp-tipped, serrated spine, in some species associated with a poison gland and presumed to be employed in defense. While functions of the catfish pectoral fin have been extensively studied, little is known about its sensory capabilities. We investigated mechanosensation in pectoral fins of the catfish Pimelodus pictus. During rhythmic swimming and when stationary, P. pictus holds the pectoral fins angled outward from the body. Work on pectoral fin mechanosensation in other species has focused on fin rays used as propulsors or in active probing. The stiff spine and relative immobility of the catfish fin suggests that its rays may not be as responsive to mechanical stimulation as those of fish with more mobile fins. In addition, the cranial barbels of catfish are putative tactile sensors, making it unclear to what extent the pectoral fins are needed for this function. Immunostaining shows extensive innervation of the fin rays, including the spine. Because minimal muscle is associated with the rays, this innervation suggests sensory function. We used extracellular recordings from afferent nerves to assess the function of these processes. Nerves responded robustly to tactile stimulation of the ventrolateral and dorsomedial surfaces of the pectoral fin, as well as the leading edge of the spine. Our findings suggest that the pectoral spine and soft rays complement the barbels as tactile sensors. Tactile sensation may contribute to the defensive function of the spine, perhaps triggering the release of poison or an escape response, or serve other roles not considered previously.