3D reconstructions of the swim bladder and the otoliths of <i>P. polleni</i> displaying the anterior projections of the swim bladder to the inner ear.

<p>(<b>A</b>) Volume rendering based on the reconstruction of the whole fish (specimen 2, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042292#pone-0042292-t002" target="_blank">Table 2</a>) in lateral view with the swim bladder (green) and the otoliths lapillus (red), sagitta (pink), and asteriscus (yellow) superimposed. The white line indicates the position of the septum. (<b>B</b>) Reconstructions of the close-up scan of the otoliths and the anterior portion of the swim bladder in (<b>B₁</b>) lateral and (<b>B₂</b>) ventral views. The swim bladder horns come close to the asteriscus. as, asteriscus; lap, lapillus; sa, sagitta; sb, swim bladder. Scale bars: (<b>A</b>) 1 cm, (<b>B</b>) 1 mm.</p

Number of specimens, range of standard length (SL) and fixative/staining method used for the investigation of swim bladder morphology as well as number of specimens, range of standard length and body weight (BW) used for auditory measurements.

<p>EtOH, ethanol; F, formalin; I₂KI, Lugol solution (2.5% potassium iodide (KI), 1.25% iodine metal (I₂) in water. Numbers in parentheses indicate number of specimens subjected to the respective treatment.</p

3D reconstructions of the swim bladder and the otoliths of <i>E. maculatus</i> displaying the rostral projections of the swim bladder to the inner ear.

<p>(<b>A</b>) Volume rendering based on the reconstruction of the whole fish (specimen 2, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042292#pone-0042292-t002" target="_blank">Table 2</a>) in lateral view with the swim bladder (green) and the otoliths lapillus (red), sagitta (pink), and asteriscus (yellow) superimposed. The white line indicates the position of the septum. (<b>B</b>) Reconstructions of the close-up scan of the otoliths and the anterior portion of the swim bladder in (<b>B₁</b>) lateral and (<b>B₂</b>) ventral views. The swim bladder horns come very close to the asteriscus. (<b>C</b>) The high-resolution close-up of another individual (specimen 4, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042292#pone-0042292-t002" target="_blank">Table 2</a>) additionally shows the membranous labyrinth and the tissue pad of the swim bladder horn displaying the close proximity to the lagena and the posterior and horizontal semicircular canals in (<b>C₁</b>) lateral and (<b>C₂</b>) ventral views. Note that anterior and horizontal semicircular canals are incomplete due to the limited scanning field. a, anterior; as, asteriscus; d, dorsal; la, lateral; lap, lapillus; sa, sagitta; sb, swim bladder; tp, tissue pad. Scale bars: (<b>A</b>) 1 cm, (<b>B</b>) 1 mm, (<b>C</b>) 500 µm.</p

Swim bladder and inner ear of <i>S. tinanti</i> in (A) lateral and (B) ventral views.

<p>The swim bladder is small and distinctly away from the inner ear. The swim bladder is shown in green; the otoliths of the inner are shown in red (lapillus  =  utricular otolith), pink (sagitta  =  saccular otolith), and yellow (asteriscus  =  lagenar otolith). Scale bar  = 1 cm.</p

Representative AEP waveforms in response to 0.5 and 1 kHz tone bursts and control recording of a dead fish.

<p>AEPs are shown 20 dB above the mean auditory threshold of each species (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042292#pone-0042292-t003" target="_blank">Table 3A</a>). Numbers indicate SPLs (dB re 1 µPa). Arrows indicate the stimulus onset.</p

Swim bladder and inner ear of <i>E. maculatus</i> in (A) lateral and (B) ventral views.

<p>The air-filled part of the swim bladder is shown in shaded green and the tissue pad in dark green. The two white openings in the tissue pad (<b>B</b>) are passages for nerves. a, anterior; as, asteriscus; asc, anterior semicircular canal; d, dorsal; hsc, horizontal semicircular canal; la, lateral; lap, lapillus; lag, lagena; psc, posterior semicircular canal; sa, sagitta; sac, sacculus; sb, swim bladder; tp, tissue pad; utr, utricle. Scale bar  = 1 mm.</p

Sound pressure level and particle acceleration levels in the three orthogonal Cartesian directions and for PAL of the three axes combined at each test frequency.

<p>SPL-sound pressure level (dB re 1 µPa), PAL-particle acceleration level (dB re 1 µm/s²) in the vertical (vert), rostrocaudal (rc), and lateral (lat) axis; PAL comb-PAL combined of the three directions (magnitude <i>sensu</i> Casper and Mann (2006) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042292#pone.0042292-Casper1" target="_blank">[22]</a> and Wysocki et al. (2009) [x]. The PAL comb was calculated based on the particle acceleration of each axis in µm/s² as 20*log(sqrt(x²+y²+z²)).</p

Mean (± s.e.m.) hearing thresholds of the cichlid species investigated.

<p>(<b>A</b>) Sound pressure level (SPL) audiograms and (<b>B</b>) Particle acceleration level (PAL) audiograms. Lab noise, cepstrum-smoothed spectra of laboratory ambient noise.</p

Swim bladder and inner ear of <i>P. polleni</i> in (A) lateral and (B) ventral views.

<p>The swim bladder horn comes close to the lagena and its otolith, the asteriscus (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042292#pone-0042292-g005" target="_blank">Figure 5</a>). a, anterior; as, asteriscus; asc, anterior semicircular canal; d, dorsal; hsc, horizontal semicircular canal; la, lateral; lap, lapillus; lag, lagena; psc, posterior semicircular canal; sa, sagitta; sac, sacculus; sb, swim bladder; utr, utricle. Scale bar  = 1 mm.</p

Mean (± s.e.m.) auditory sensitivity of the four cichlid species investigated.

<p><i>N</i>, number of specimens; nm, no measurement taken; nr, no response.</p