title: Vocal production complexity correlates with neural instructions in the oyster toadfish (Opsanus tau).
abstract: Sound communication is fundamental to many social interactions and essential to courtship and agonistic behaviours in many vertebrates. The swimbladder and associated muscles in batrachoidid fishes (midshipman and toadfish) is a unique vertebrate sound production system, wherein fundamental frequencies are determined directly by the firing rate of a vocal-acoustic neural network that drives the contraction frequency of superfast swimbladder muscles. The oyster toadfish boatwhistle call starts with an irregular sound waveform that could be an emergent property of the peripheral nonlinear sound-producing system or reflect complex encoding in the central nervous system. Here, we demonstrate that the start of the boatwhistle is indicative of a chaotic strange attractor, and tested whether its origin lies in the peripheral sound-producing system or in the vocal motor network. We recorded sound and swimbladder muscle activity in awake, freely behaving toadfish during motor nerve stimulation, and recorded sound, motor nerve and muscle activity during spontaneous grunts. The results show that rhythmic motor volleys do not cause complex sound signals. However, arrhythmic recruitment of swimbladder muscle during spontaneous grunts correlates with complex sounds. This supports the hypothesis that the irregular start of the boatwhistle is encoded in the vocal pre-motor neural network, and not caused by peripheral interactions with the sound-producing system. We suggest that sound production system demands across vocal tetrapods have selected for muscles and motorneurons adapted for speed, which can execute complex neural instructions into equivalently complex vocalisations.
authors.affiliation: Marine Biological Laboratory, Woods Hole, MA 02543, USA Department of Biology, University of Southern Denmark, 5230 Odense M, Denmark coen@biology.sdu.dk.
authors.forename: Coen P H
authors.initials: CP
authors.lastname: Elemans
authors.affiliation: The Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA Department of Biology, University of Minnesota Duluth, Duluth, MN 55812, USA.
authors.forename: Allen F
authors.initials: AF
authors.lastname: Mensinger
authors.affiliation: The Whitman Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Lawrence C
authors.initials: LC
authors.lastname: Rome
mesh_terms: D000400:Air Sacs / Q000294:innervation / Q000502:physiology*; D000818:Animals; D024541:Batrachoidiformes / Q000502:physiology*; D004558:Electric Stimulation; D009046:Motor Neurons / Q000502:physiology; D017711:Nonlinear Dynamics; D010507:Periodicity; D013016:Sound; D014828:Vocalization, Animal / Q000502:physiology*
keywords: Acoustic communication; Deterministic chaos; Sound production; Superfast muscle; Swim bladder; Toadfish