title: Effects of aerial hypoxia and temperature on pulmonary breathing pattern and gas exchange in the South American lungfish, Lepidosiren paradoxa.
abstract: The South American lungfish Lepidosiren paradoxa is an obligatory air-breathing fish possessing well-developed bilateral lungs, and undergoing seasonal changes in its habitat, including temperature changes. In the present study we aimed to evaluate gas exchange and pulmonary breathing pattern in L. paradoxa at different temperatures (25 and 30°C) and different inspired O2levels (21, 12, 10, and 7%). Normoxic breathing pattern consisted of isolated ventilatory cycles composed of an expiration followed by 2.4±0.2 buccal inspirations. Both expiratory and inspiratory tidal volumes reached a maximum of about 35mlkg-1, indicating that L. paradoxa is able to exchange nearly all of its lung air in a single ventilatory cycle. At both temperatures, hypoxia caused a significant increase in pulmonary ventilation (V̇E), mainly due to an increase in respiratory frequency. Durations of the ventilatory cycle and expiratory and inspiratory tidal volumes were not significantly affected by hypoxia. Expiratory time (but not inspiratory) was significantly shorter at 30°C and at all O2levels. While a small change in oxygen consumption (V̇O2) could be noticed, the carbon dioxide release (V̇CO2, P=0.0003) and air convection requirement (V̇E/V̇O2, P=0.0001) were significantly affected by hypoxia (7% O2) at both temperatures, when compared to normoxia, and pulmonary diffusion capacity increased about four-fold due to hypoxic exposure. These data highlight important features of the respiratory system of L. paradoxa, capable of matching O2demand and supply under different environmental change, as well as help to understand the evolution of air breathing in lungfish.
authors.affiliation: College of Agricultural and Veterinarian Sciences, São Paulo State University, Brazil; National Institute of Science and Technology on Comparative Physiology, Rio Claro, Brazil.
authors.forename: Glauber S F
authors.initials: GSF
authors.lastname: da Silva
authors.affiliation: Master Program in Animal Diversity, Federal University of Bahia, Brazil.
authors.forename: Daniela A D N
authors.initials: DADN
authors.lastname: Ventura
authors.affiliation: College of Agricultural and Veterinarian Sciences, São Paulo State University, Brazil; National Institute of Science and Technology on Comparative Physiology, Rio Claro, Brazil.
authors.forename: Lucas A
authors.initials: LA
authors.lastname: Zena
authors.affiliation: Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
authors.forename: Humberto
authors.initials: H
authors.lastname: Giusti
authors.affiliation: Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
authors.forename: Mogens L
authors.initials: ML
authors.lastname: Glass
authors.affiliation: School of Philosophy, Sciences and Literature of Ribeirão Preto, University of São Paulo, Brazil; National Institute of Science and Technology on Comparative Physiology, Rio Claro, Brazil. Electronic address: wklein@usp.br.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Klein
mesh_terms: D000818:Animals; D005399:Fishes; D000860:Hypoxia; D008168:Lung / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012119:Respiration
chemical_list: D010100:Oxygen
keywords: Buccal pump; Dipnoi; Lung ventilation; Thermal variation