title: Vocal differentiation parallels development of auditory saccular sensitivity in a highly soniferous fish.
abstract: Vocal differentiation is widely documented in birds and mammals but has been poorly investigated in other vertebrates, including fish, which represent the oldest extant vertebrate group. Neural circuitry controlling vocal behaviour is thought to have evolved from conserved brain areas that originated in fish, making this taxon key to understanding the evolution and development of the vertebrate vocal-auditory systems. This study examines ontogenetic changes in the vocal repertoire and whether vocal differentiation parallels auditory development in the Lusitanian toadfish Halobatrachus didactylus (Batrachoididae). This species exhibits a complex acoustic repertoire and is vocally active during early development. Vocalisations were recorded during social interactions for four size groups (fry: <2 cm; small juveniles: 2-4 cm; large juveniles: 5-7 cm; adults >25 cm, standard length). Auditory sensitivity of juveniles and adults was determined based on evoked potentials recorded from the inner ear saccule in response to pure tones of 75-945 Hz. We show an ontogenetic increment in the vocal repertoire from simple broadband-pulsed 'grunts' that later differentiate into four distinct vocalisations, including low-frequency amplitude-modulated 'boatwhistles'. Whereas fry emitted mostly single grunts, large juveniles exhibited vocalisations similar to the adult vocal repertoire. Saccular sensitivity revealed a three-fold enhancement at most frequencies tested from small to large juveniles; however, large juveniles were similar in sensitivity to adults. We provide the first clear evidence of ontogenetic vocal differentiation in fish, as previously described for higher vertebrates. Our results suggest a parallel development between the vocal motor pathway and the peripheral auditory system for acoustic social communication in fish.
authors.affiliation: Institute of Science and Environment, University of Saint Joseph, Rua de Londres 16, Macau S.A.R., People's Republic of China Departamento de Biologia Animal and Centre for Ecology, Evolution and Environmental Changes (cE3c), Universidade de Lisboa, Bloco C2 Campo Grande, Lisbon 1749-016, Portugal raquel.vasconcelos@usj.edu.mo.
authors.forename: Raquel O
authors.initials: RO
authors.lastname: Vasconcelos
authors.affiliation: Departments of Psychology and Biology, University of Washington, Seattle, WA 98195, USA.
authors.forename: Peter W
authors.initials: PW
authors.lastname: Alderks
authors.affiliation: Institute of Science and Environment, University of Saint Joseph, Rua de Londres 16, Macau S.A.R., People's Republic of China Departamento de Biologia Animal and Centre for Ecology, Evolution and Environmental Changes (cE3c), Universidade de Lisboa, Bloco C2 Campo Grande, Lisbon 1749-016, Portugal.
authors.forename: Andreia
authors.initials: A
authors.lastname: Ramos
authors.affiliation: Departamento de Biologia Animal and Centre for Ecology, Evolution and Environmental Changes (cE3c), Universidade de Lisboa, Bloco C2 Campo Grande, Lisbon 1749-016, Portugal.
authors.forename: Paulo J
authors.initials: PJ
authors.lastname: Fonseca
authors.affiliation: MARE - Marine and Environmental Sciences Centre, Departamento de Biociências, ISPA - Instituto Universitário, Rua Jardim do Tabaco 34, Lisbon 1149-041, Portugal.
authors.forename: M Clara P
authors.initials: MC
authors.lastname: Amorim
authors.affiliation: Departments of Psychology and Biology, University of Washington, Seattle, WA 98195, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Sisneros
mesh_terms: D000818:Animals; D001309:Auditory Threshold / Q000502:physiology*; D024541:Batrachoidiformes / Q000254:growth & development* / Q000502:physiology*; D005071:Evoked Potentials; D005260:Female; D008297:Male; D012444:Saccule and Utricle / Q000502:physiology*; D014828:Vocalization, Animal / Q000502:physiology*
keywords: Acoustic communication; Batrachoididae; Hearing; Ontogeny; Vocal differentiation