Functional properties and projection areas of cutaneous receptors in catfish

Abstract

Neurophysiological studies were conducted in a species of catfish,Ictalurus nebulosus where specialized living habits are coupled with enlargement of certain nervous system structures. These fish, mainly lake bottom dwellers, recognize food only by touch. The entire body surface contains structures resembling mammalian taste buds; the ganglia of the fifth and seventh nerves (receiving input from barbel and head skin) are much larger than in other fish of similar size; the facial lobes, macroscopically invisible in most fish, are prominent. Early anatomical studies reported that the cutaneous buds, considered chemosensitive, project to the brainstem in parallel with tactile paths, but the two modalities remain separate. The facial lobes, the projection area of the cutaneous buds via the seventh nerve, were considered a pure chemosensory structure. In feeding behavior, the chemosensory system was proposed to distinguish sapid from nonsapid substances, the tactile system to localize the food substances.