Effects of environmental hypercapnia on pulmonary ventilation of the South American lungfish

Abstract

Aquatic hypercapnia at PCO 2 of 55 mmHg significantly increased pulmonary ventilation in the South American lungfish Lepidosiren paradoxa, whereas no significant increases occurred when hypercapnia was applied to the gas phase with or without concomitant aquatic hypercapnia. On return from gas phase hypercapnia to inspiration of air there was a marked transient increase of ventilation. This post-hypercapnic response is discussed in relation to the possible presence of upper airway or pulmonary CO 2 receptors that inhibit pulmonary ventilation during hypercapnia. Post-hypercapnic hyperpnea has been reported for various groups of reptiles and for anuran amphibians. The occurrence of post-hypercapnic hyperpnea in Lepidosiren adds new information related to the evolution of respiratory regulation in vertebrates. 2001 The Fisheries Society of the British Isles

Air‐breathing fishes in aquaculture. What can we learn from physiology?

“…In tropical aquaculture ponds with high stocking density, no aeration and little water exchange, CO 2 is likely to reach high levels because air‐breathing fishes typically obtain oxygen from the air breathing organ, but excrete CO 2 across their gills into the water (Evans et al , ; De Lima Boijink et al , ). One exception may be L. paradoxa which appears to increase lung rather than gill ventilation during exposure to hypercapnia (Sanchez & Glass, ). In many tropical areas, water is rather poorly buffered and the putatively high CO 2 level would therefore cause considerable reductions in water pH.…”

Striped catfish (Pangasianodon hypophthalmus) use air‐breathing and aquatic surface respiration when exposed to severe aquatic hypercarbia

“…In the clown knifefish, Chitala ornata , environmental hypercarbia stimulated air breathing but had no effect on gill ventilation (Tuong et al, 2018). However, an inhibition of gill breathing at the onset of air breathing has also been observed in several other species although in most there was an initial increase in gill ventilation before the onset of air breathing (Graham & Baird, 1982; Johansen & Lenfant, 1968; Johansen et al, 1967, 1970; Sanchez & Glass, 2001; Sanchez et al, 2005). The decline in gill ventilation may serve to minimize CO 2 influx into the blood of P. hypophthalmus .…”

“…Hypercarbia induced air‐breathing has been documented in several facultative air‐breathing species (e.g., de Lima Boijink et al, 2010; Sanchez & Glass, 2001; Sanchez et al, 2005; Tuong et al, 2018). However, increased air‐breathing has only been documented previously in response to aquatic hypoxia in P. hypophthalmus (Lefevre et al, 2011; Thomsen et al, 2017) and not hypercarbia (Thomsen et al, 2017).…”

Combined ventilatory responses to aerial hypoxia and temperature in the South American lungfish Lepidosiren paradoxa

“…Both depend on pulmonary ventilation (V E ) for O 2 uptake (V O2 ) (Lenfant et al, 1970), whereas Neoceratodus (Australian) possess a single lung combined with gills that suffice to sustain total metabolism in normoxic water (Fritsche et al, 1993). Among several respiratory functions shared by tetrapods and lungfish, such as pulmonary diffusing capacity (Bassi et al, 2005;de Moraes et al, 2005), pulmonary surfactant (Orgeig and Daniels, 1995) and hyperpnoea after-hypercapnia response (Glass et al, 2009;Sanchez and Glass, 2001), it appears that both possess central CO 2 /pH chemoreceptors (Sanchez et al, 2001b;Amin-Naves et al, 2007a, b).…”