Solitary chemoreceptor cells of Ciliata mustela (Gadidae, Teleostei) are tuned to mucoid stimuli

Summed potentials were recorded from the dorsal recurrent facial nerve innervating the solitary chemoreceptor cells on the anterior dorsal fin (ADF), from the ventral recurrent facial nerve innervating both taste buds and solitary chemoreceptor cells on the pectoral (PEC) and pelvic (PEL) fins, and from the anterior dorsal fin muscles in the rockling, Ciliata mustela. There is little overlap between the sumulus spectra of solitary chemoreceptor cells and taste buds. The ADF solitary cells are particularly sensitive to body mucus (skin water) of non-congeners like Gadus, Solea, Cottus, Mugil, Zoarces, Gaidropsarus, and Encheliopus, but insensitive to amino acids and a variety of body fluids of fish, invertebrates, and extracts of potential stimuli like algae and sand. Pectoral and pelvic fins are particularly sensitive to amino acids, body fluids of fish and invertebrates, but less sensitive to skin mucus of fish, probably due to the abundance of taste buds. Active sampling by undulation of the anterior dorsal fin is essential for proper functioning; it induces disadaptation of the receptor elements. Solitary chemoreceptor cells provide, apparently, cues to discriminate between conspecifics and non-conspecifics. It is unlikely that they are involved in pheromone detection.