Table 1.
Description of the behavioural repertoire shown during dyadic male-male and female-female interactions of M. thoracata.
Fig 1.
Mean (+ SE) relative pectoral spine length of male and female Megalechis thoracata.
Different letters indicate statistically significant differences between sexes. PSL—total length of pectoral spine, TL—total fish length.
Fig 2.
Screen shot of a video recording showing two males in an agonistic contest.
The illustration shows the right male approaching the opponent, shortly before uttering a bark.
Fig 3.
Screen shot of video recording during a male-male aggressive interaction.
This screen shot shows the typically threatening fin display with fins spread and the caudal part of the right male erected in a distinct angle. The right fish produced a thump in this oblique anti-parallel position relative to the conspecific.
Fig 4.
Screen shot of video recording illustrating a female-female agonistic encounter.
The right female emitted a series of crackles while pursuing the other female.
Fig 5.
(A) Sonagram (top) and oscillogram (below) and (B) cepstrum-smoothed power spectrum of a monopartite bark of a male M. thoracata produced during an aggressive encounter.
The spectrum shows three harmonics (1st, 2nd, 3rd) with the highest energy found in the second harmonic. Sampling rate 22 kHz. Hanning filter, overlap 75%, (A) filter bandwidth 20 Hz, (B) filter bandwidth 1 Hz, number of coefficients 350.
Fig 6.
(A) Sonagram (top) and oscillogram (below) and (B) cepstrum-smoothed power spectrum of the bipartite bark of a male M. thoracata.
The spectrum reveals three harmonics (1st, 2nd, 3rd) within the second sound part (white arrow) with the highest energy found in the second harmonic. The oscillogram shows lower amplitude in the first part (light blue arrow). Sampling rate 11 kHz. Hanning filter, overlap 75%, (A) filter bandwidth 20 Hz, (B) filter bandwidth 1 Hz, number of coefficients 170.
Fig 7.
(A) Sonagram (top) and oscillogram (below) and (B) cepstrum-smoothed power spectrum of a monopartite thump of a male M. thoracata uttered in an agonistic context.
The dominant frequency is indicated in (B). Sampling rate 11 kHz. Hanning filter, overlap 75%, (A) filter bandwidth 20 Hz, (B) filter bandwidth 1 Hz, number of coefficients 80.
Fig 8.
(A) Sonagram (top) and oscillogram (below) and (B) cepstrum-smoothed power spectrum of crackles of a female M. thoracata produced in an agonistic context.
The oscillogram shows five sound elements. The white arrow indicates the main element, followed by a train of pulses. The dominant frequency is indicated in the cepstrum-smoothed power spectrum in (B). Sampling rate 11 kHz. Hanning filter, overlap 75%, (A) filter bandwidth 100 Hz, (B) filter bandwidth 1 Hz, number of coefficients 20.
Fig 9.
Mean (+ SE) sound duration of male barks and thumps (N = 7) and of female crackles (N = 8).
Different letters indicate statistically significant differences between sound types.
Fig 10.
Mean (+ SE) sound pressure level of male barks and thumps (N = 7) and of female crackles (N = 8).
Different letters indicate statistically significant differences between sound types.
Fig 11.
Mean (+ SE) dominant frequency of male barks and thumps (N = 7) and of female crackles (N = 8).
Different letters indicate statistically significant differences between sound types.
Table 2.
Correlations between mean sound characteristics (sound duration, dominant frequency, sound pressure level) of male and female sound types and morphological variables (total length, pectoral spine length, relative pectoral spine length).
Fig 12.
Mean (± SE) auditory sensitivities of male (N = 6) and female (N = 6) M. thoracata.
Fig 13.
Mean auditory sensitivities of male and female M. thoracata (solid lines) in relation to spectral characteristics of sounds (dotted lines).
Power spectra of sounds were averaged of sounds of all individuals and are shown in relative amplitude values (right Y-axis).
Fig 14.
AEP-audiograms of all representatives of the family Callichthyidae investigated in the recent and in prior studies.
Megalechis thoracata (current study, females and males pooled), Corydoras paleatus [33], Corydoras sodalis and Dianema urostriatum [52].