Chemoreception in the Lateral-line System of the Bony Fish

Abstract

In the shark, Katsuki, (one of the present authors) et al. (1969) found that the free neuromasts, the so-called pit organs, broadly distributed on the dorsal surface of the body and innervated by the lateral-line nerve fibers, were very responsive to monovalent cations, but their responses were inhibited by some of divalent cations like Ca and Mg. Various anions and sugars were ineffective . While not external taste buds , those receptors were considered to be chemoreceptors responsive to changes in the concentration of those cations in the environment . In teleosts , on the other hand , since the beginning of the twentieth century many species of bony fishes have been behaviorally found to be responsive to chemical stimuli not only in the mouth , the pharynx and the gill cavity , but also on the entire surface of the body including barbels and fins . It was also known in Ameiurus that with the cutting of the branch of the facial nerve , the responses to chemical stimuli on the flank no longer occurred ( Parker 1912 ). Based on those reports it is generally believed that the outer surfaces of most fishes may be receptive to stimulation by chemical substance of a mildly irritating kind ( Hasler4 ) 1957 , Bardachl > 1967 ). Although many behavioral studies have been conducted , the electrophysiological studies on the chemical sense of fishes have been performed only on two materials , one is the palatal organ of the carp used by Konishi and Zotterman7 ) ( 1963 ) and the other is the appendage , fin or barbel , of a few fishes by Bardach et al . 2 ~ ( 1967 ). No other electrophysiological studies have been reported to confirm the chemical sense on the body surface . Dijkgraaf3 ) ( 1963 ) published an extensive review of the functioning and significance of the lateral-line organs of both the canal and free neuromasts , but he did not review the chemical sensation by those organs .