Table 1.

Summary of sex differences in physical traits, EOD frequency and EOD modulations

TraitMalesFemales1
Body mass (g)34.8±5.732.2±3.3
EOD frequency (Hz)21052.6±22.71101.4±14.4
EOD modulations (EODMs, chirps + GFRs)3:
Total number424.6±4.514.0±3.3
By type3:
All chirps (single- and multi-peaked)
Number produced418.3±4.26.8±2.85
% of total EODMs68.3±7.940.0±9.5*
Positive FM (Hz)170.7±10.6167.3±12.2
Duration (s)0.090±0.0110.060±0.021
Multi-peaked chirps46.0±2.10.4±0.3*
All gradual frequency rises (GFRs)
Number produced46.3±1.26.6±1.5
% of total EODMs31.7±7.960.0±9.5*
Positive FM (Hz)12.8±2.48.2±1.2
Duration (s)1.06±0.330.75±0.48
Multi-peaked GFRs42.3±0.51.6±0.5
  • Values are means ± s.e.m.

  • * Statistically significant sex difference; unpaired t-test, P<0.05.

  • 1 For body mass, N=5 males, 6 females. For EOD frequency, N=11 males, 10 females. For EOD modulations, N=11 males, 8 females.

  • 2 Temperature compensated to that expected at 26.0°C (see Materials and methods).

  • 3 See Fig. 1, Materials and methods and Results for a description of EOD modulation types.

  • 4 Since stimulus frequency did not affect the production of EODMs (see Fig. 4 and Results) and all fish received the same set of stimuli, data are pooled from all six 4-min recordings (five recordings with different stimuli and one baseline recording).

  • 5 Unpaired t-test (males versus females), P=0.053.