Contribution to the study of acoustic communication in two Belgian river bullheads (Cottus rhenanus and C. perifretum) with further insight into the sound-producing mechanism

Abstract

BackgroundThe freshwater sculpins (genus Cottus) are small, bottom-living fishes widely distributed in North America and Europe. The taxonomy of European species has remained unresolved for a long time due to the overlap of morphological characters. Sound production has already been documented in some cottid representatives, with sounds being involved in courtship and agonistic interactions. Although the movements associated with sound production have been observed, the underlying mechanism remains incomplete. Here, we focus on two closely related species from Belgium: C. rhenanus and C. perifretum. This study aims 1) to record and to compare acoustic communication in both species, 2) to give further insight into the sound-producing mechanism and 3) to look for new morphological traits allowing species differentiation.ResultsBoth Cottus species produce multiple-pulsed agonistic sounds using a similar acoustic pattern: the first interpulse duration is always longer, making the first pulse unit distinct from the others. Recording sound production and hearing abilities showed a clear relationship between the sound spectra and auditory thresholds in both species: the peak frequencies of calls are around 150 Hz, which corresponds to their best hearing sensitivity. However, it appears that these fishes could not hear acoustic signals produced by conspecifics in their noisy habitat considering their hearing threshold expressed as sound pressure (~ 125 dB re 1 μPa). High-speed video recordings highlighted that each sound is produced during a complete back and forth movement of the pectoral girdle.ConclusionsBoth Cottus species use an acoustic pattern that remained conserved during species diversification. Surprisingly, calls do not seem to have a communicative function. On the other hand, fish could detect substrate vibrations resulting from movements carried out during sound production. Similarities in temporal and spectral characteristics also suggest that both species share a common sound-producing mechanism, likely based on pectoral girdle vibrations. From a morphological point of view, only the shape of the spinelike scales covering the body allows species differentiation.

Auditory evoked potential audiograms in post-settlement stage individuals of coral reef fishes

“…Presence or absence of response to sounds of different intensities and frequencies allows the measurement of AEP thresholds. The experimental setup was similar to that used for previous studies (Parmentier et al, 2009;Colleye et al, 2013). No anesthetics or neuromuscular-blocking drug were used during the AEP recordings.…”

Sound production to electric discharge: sonic muscle evolution in progress inSynodontisspp. catfishes (Mochokidae)

“…Sound levels at each frequency were presented at up to 158 dB re 1 mPa and attenuated in 6 dB steps until a threshold level was determined. Recording of evoked potentials and determination of threshold followed the same procedure description given by Colleye et al [20].…”

“…(b) Hearing thresholds measurement: experimental set-up Auditory thresholds were determined by using the auditory evoked potential (AEP) recording technique [19] with the experimental set-up described in detail by Colleye et al [20], but at a temperature of 268C. The presentation of sound stimuli and the determination of thresholds followed the detailed description given by Parmentier et al [21].…”

Multiple exaptations leading to fish sound production

“…Producing sound involves a vibration coupled to the medium (Bradbury & Vehrencamp, ). Five basic mechanisms have been documented in teleost communication: (i) muscular vibrations of a membrane or sac (Fine, King, & Cameron, ; Millot, Vandewalle, & Parmentier, ), (ii) stridulation (Bertucci, Ruppé, Wassenbergh, Compère, & Parmentier, ; Fine, King, Friel, Loesser, & Newton, ; Parmentier et al ., ), (iii) forced flow through a small orifice (Fish & Mowbray, ; Lagardère & Ernande, ; Wahlberg & Westerberg, ; Wilson, Batty, & Dill, ), (iv) muscular vibration of appendages (Colleye, Ovidio, Salmon, & Parmentier, ; Ladich, ; Parmentier et al ., ) and (v) percussion on a substrate (Colleye et al ., ). Moreover, although multiple submechanisms have been described, most fall into two categories: (i) muscles that directly or indirectly insert on the swim bladder and (ii) stridulatory mechanisms involving the rubbing of bones.…”