Comparative neurobiology of vocal behaviour in teleost fishes

The vocal motor system of teleost fishes provides the opportunity to describe identified sets of neurons and circuits that underlie an easily defined, sex-dependent behavior in a vertebrate preparation. First, there is a single pair of muscles and motor nuclei that are dedicated to sound production. Second, the comprehensive mapping suggested by a recent study of transneuronal transport of biocytin in the brainstem provides an immediate guide to a causal analysis of the entire vocal motor network. Third, the discovery of sex-specific traits in the vocal system presents a unique opportunity to study the morpho-physiological correlates of intraspecific divergence in vocal behavior. We have primarily studied vocal control mechanisms in marine species. Interspecific studies have identified a divergence in central brain and peripheral sonic-swimbladder traits between two distantly related orders, the Batrachoidiformes (midshipman and toadfish) and Scorpaeniformes (sculpin and sea robins). Ontogenetic studies have focused on the plainfin midshipman, Porichthys notatus, which has two male morphs with differing reproductive tactics. Sex-and morph-specific vocal behaviors are paralleled by a divergence in the developmental trajectories of vocal motor traits resulting in distinct adult vocal phenotypes. Hence, neuroanatomical and physiological studies now reveal a divergence in vocal mechanisms that, we propose, underlies the generation of species-and sex-typical vocalizations.