SOMATOTOPY IN THE REPRESENTATION OF THE PECTORAL FIN AND FREE FIN RAYS IN THE SPINAL CORD OF THE SEA ROBIN,PRIONOTUS CAROLINUS

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Abstract
Sea robins possess modified pectoral fin rays which are chemosensory although lacking taste buds or olfactory receptors. These fin rays are innervated only by spinal nerves which terminate in accessory spinal lobes, enlargements of the dorsal horn in the rostral spinal cord. Horseradish peroxidase was used as a neuronal tracer to determine the representation of each fin ray nerve in the spinal cord. The nerve innervating each fin ray terminates in a single accessory lobe, with the ventral fin ray terminating in the caudal accessory lobe and the dorsal fin ray in the rostral major accessory lobe. The pectoral fin itself is represented in a minor spinal enlargement lying rostral of the major accessory lobes.