Aerial ventilatory responses of the mudskipper, Periophthalmodon schlosseri, to altered aerial and aquatic respiratory gas concentrations

Abstract

Periophthalmodon schlosseri is a mudskipper which uses the vascularized buccopharyngeal cavity as a respiratory organ. The fish construct mud burrows that contain hypoxic water, but store air inside the burrows. Because the burrow gas is frequently hypoxic and hypercapnic, the effects of altered respiratory gas concentrations on the aerial ventilation frequency (VF), inspiratory tidal volume (VT) and minute volume (VM=VF×VT) of P. schlosseri were studied by pneumotachography. Both total buccopharyngeal gas volume (VBP) and VT scaled significantly with body mass (mass exponents=1.10 and 1.03, respectively), and VT/VBP was 0.54±0.05 (S.E.M., n=6). VBP, expressed as a percentage of body volume, was much higher (16%) than in other air-breathing gobies (2–4%). When fish respired in normoxic air and water, VF was 0.25±0.04 breaths min−1, VT 7.6±0.6 ml 100 g−1, and VM 1.80±0.18 ml 100 g−1 min−1. Aquatic hypoxia did not significantly affect VF, VT, or VM. In both moderate (PO2=10 kPa) and severe (PO2=5 kPa) aerial hypoxia, VF and VM increased significantly. VT increased significantly only during severe aerial hypoxia. In aerial hypercapnia, VF and VM increased significantly.