Comparisons Between Electrosensory and Mechanosensory Lateral Line Systems

Abstract

A volume on the lateral line would be incomplete without a consideration of its closely allied sense, electroreception. Electroreception is usually considered a specialized lateral line sense (Dijkgraaf 1962; Lissmann 1967; Szabo 1974). The marked similarities between mechanosensory lateral line (hereafter referred to as lateral line) and electrosensory systems, including embryology and morphology of receptors, receptor innervation and distribution, and CNS anatomy, are generally appreciated and held by most to reflect a close evolutionary relationship between these so-called lateralis senses. Since the discovery of electroreception 30 years ago in weakly electric teleost fishes (Lissmann 1958; Bennett and Grundfest 1959; Bullock et al. 1961; Fessard and Szabo 1961), the favored hypothesis has been that electroreceptors evolved as specialized derivatives of preexisting lateral line neuromasts (Lissmann 1958, 1967; Mullinger 1964; Bennett 1971). Major support for this hypothesis was the phylogenetic distribution of the two senses as it was then known. In the last volume on the lateral line, published 20 years ago, Lissmann (1967) stated the case simply: “The ordinary neuromast is the rule, the ampullary organ [electroreceptor] the exception.”