Table 1.
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.
Table 2.
Overview of specimens of P. polleni and E. maculatus subjected to microCT imaging including details about voxel size, image resolution, and number of images used for the 3D reconstructions.
Figure 1.
Representative AEP waveforms in response to 0.5 and 1 kHz tone bursts and control recording of a dead fish.
AEPs are shown 20 dB above the mean auditory threshold of each species (see Table 3A). Numbers indicate SPLs (dB re 1 µPa). Arrows indicate the stimulus onset.
Table 3.
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.
Figure 2.
Swim bladder and inner ear of S. tinanti in (A) lateral and (B) ventral views.
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.
Figure 3.
Swim bladder and inner ear of H. guttatus in (A) lateral and (B) ventral views.
The swim bladder is ‘normal’ sized without contact to the inner ear. The swim bladder is shown in green; the otoliths of the inner are shown in red (lapillus), pink (sagitta), and yellow (asteriscus). Scale bar = 1 cm.
Figure 4.
Ventrolateral view of the left inner ear and the anterior most part of the left swim bladder horn in P. polleni (specimen 1,
Table 2). A tissue sheath envelopes the swim bladder horn (A1). In (A2) the swim bladder horn is shown after the removal of the tissue sheath. asc, anterior semicircular canal; hsc, horizontal semicircular canal; lag, lagena; sa, sagitta; sb, swim bladder horn; sb + ti, swim bladder horn with enveloping tissue sheath; utr, utricle. Scale bars = 1 mm.
Figure 5.
3D reconstructions of the swim bladder and the otoliths of P. polleni displaying the anterior projections of the swim bladder to the inner ear.
(A) Volume rendering based on the reconstruction of the whole fish (specimen 2, see Table 2) 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) Reconstructions of the close-up scan of the otoliths and the anterior portion of the swim bladder in (B1) lateral and (B2) ventral views. The swim bladder horns come close to the asteriscus. as, asteriscus; lap, lapillus; sa, sagitta; sb, swim bladder. Scale bars: (A) 1 cm, (B) 1 mm.
Figure 6.
Swim bladder and inner ear of P. polleni in (A) lateral and (B) ventral views.
The swim bladder horn comes close to the lagena and its otolith, the asteriscus (see also Figure 5). 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.
Figure 7.
3D reconstructions of the swim bladder and the otoliths of E. maculatus displaying the rostral projections of the swim bladder to the inner ear.
(A) Volume rendering based on the reconstruction of the whole fish (specimen 2, see Table 2) 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) Reconstructions of the close-up scan of the otoliths and the anterior portion of the swim bladder in (B1) lateral and (B2) ventral views. The swim bladder horns come very close to the asteriscus. (C) The high-resolution close-up of another individual (specimen 4, Table 2) 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 (C1) lateral and (C2) 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: (A) 1 cm, (B) 1 mm, (C) 500 µm.
Figure 8.
Posterior views of the anterior most swim bladder extension and occipital region of the skull of E. maculatus.
(A) The left swim bladder extension was removed and exposes the tissue covering the foramen in the exoccipital bone (specimen 3 in Table 2). On the right side, the anterior most swim bladder extension and the exposed inner ear can be seen. In another specimen (specimen 4 in Table 2) the swim bladder extension and tissue were both removed in order to expose the foramen (B). On the right side, the anterior most swim bladder extension was left in position. The inner ears on both sides are still covered by bone. asc, anterior semicircular canal; fo, exoccipital foramen; hsc, horizontal semicircular canal; n, nerve; psc, posterior semicircular canal; sa, sagitta; sb, swim bladder extension; sc, spinal chord; ti, tissue sheet. Scale bars = 1 mm.
Figure 9.
Swim bladder and inner ear of E. maculatus in (A) lateral and (B) ventral views.
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) 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.
Table 4.
Mean (± s.e.m.) auditory sensitivity of the four cichlid species investigated.
Figure 10.
Mean (± s.e.m.) hearing thresholds of the cichlid species investigated.
(A) Sound pressure level (SPL) audiograms and (B) Particle acceleration level (PAL) audiograms. Lab noise, cepstrum-smoothed spectra of laboratory ambient noise.
Table 5.
Full factorial general linear models (GLM) using ‘frequency’ as repeated measurements and ‘species’ as fixed factor were calculated for all four species from 0.1 up to 0.5 kHz or with S. tinanti removed from the dataset for the full frequency range tested.