Table 1 Cardiorespiratory and HRV parameters in L. paradoxa.

Experimental conditions: after instrumentation (Post-surgery; n = 9), recovered resting fish (Control; n = 8), with cholinergic receptor blockade (Atropine; n = 6), or total blockade of β-adrenergic and cholinergic receptors (Atropine + Propranolol; n = 6). Following instrumentation, lungfish was allowed to recover for at least 24 hours before measurements. Data are means ± SEM. Different superscript letters indicate significant differences [analysis of variance (ANOVA) with Tukey’s post hoc test, P < 0.05]. SDNN, SD of all normal-to-normal intervals; RMSSD, square root of the mean squared differences between each successive RRi and the mean interval; PSD, power spectral density.

ParametersExperimental groups
Post-surgeryControlAtropineAtropine + Propranolol
O2 uptake per breath (ml breath−1 kg−1)0.11 ± 0.02A0.83 ± 0.07B0.29 ± 0.05A,C0.43 ± 0.08C
Embedded ImageO2 (ml kg−1 hour−1)23.6 ± 1.8A10.6 ± 0.8B24.2 ± 3.1A20.4 ± 2.5A
fR (breaths hour−1)11.5 ± 1.7A1.7 ± 0.1B7.3 ± 1.5C5.9 ± 1.6C
Tidal volume (ml kg−1)27.9 ± 1.8A25.3 ± 1.6A26.7 ± 1.7A34.1 ± 1.9B
Air-breathing cycle (s)8.8 ± 0.4A9.5 ± 0.4A8.6 ± 0.3A9.7 ± 0.4A
fH (beats min−1)38.8 ± 1.4A29.5 ± 1.5B39.2 ± 1.9A36.3 ± 2.2A
RR mean (ms)1547.4 ± 58.8A1,947.7 ± 74.7B1548.8 ± 69.8A1682.8 ± 90.4A
RR variance (ms2)4953.2 ± 1187.8A28,244.1 ± 3,344.7B1834.9 ± 491.5A3690.9 ± 1311.4A
SDNN (ms)66.6 ± 8.1A192.4 ± 16.5B40.4 ± 6.3A54.9 ± 11.7A
RMSSD (ms)40.7 ± 4.2A102.8 ± 9.8B22.5 ± 5.5A19.9 ± 4.9A
PSD (ms2)3664.0 ± 437.3A26,957.5 ± 2,791.1B998.9 ± 364.7A2903.7 ± 970.1A