Interplay between the morphometry of the lungs and the mode of locomotion in birds and mammals

Abstract

We studied the lung diffusion parameters of two species of birds and two species of mammals to explore how structural and functional features may be paralleled by differences in life style or phylogenetic origin. We used two fast-flying species (one mammal and one bird), one running mammal and one bird species that flies only occasionally as models. The harmonic mean thickness of the air-blood barrier was very thin in the species we studied. An exception was the Chilean tinamou Notoprocta perdicaria, which only flies occasionally. It showed an air-blood barrier as thick as that of flightless Galliformes. We found that the respiratory surface density was significantly greater in flying species compared to running species. The estimated values for the oxygen diffusion capacity, D t O 2 follow the same pattern: the highest values were obtained in the flying species, the bat and the eared dove. The lowest value was in N. perdicaria. Our findings suggest that the studied species show refinements in their morphometric lung parameters commensurate to their energetic requirements as dictated by their mode of locomotion, rather than their phylogenetic origin. The air-blood barrier appears to be thin in most birds and small mammals, except those with low energetic requirements such as the Chilean tinamou. In the species we studied, the respiratory surface density appears to be the factor most responsive to the energetic requirements of flight.

Comparison of the Oxygen Diffusing Capacity of the Picui Ground Dove (Columbina picui) with Other Doves of Chile

“…When we consider the oxygen diffusing capacity in the three species we observed that the larger species (Z. auriculata and M. melanoptera) have high values similar to those reported for Z. auriculata (Figueroa et al) (Canals et al, 2005b;Figueroa et al) we estimated the expected D t O 2 for our species. While for Z. auriculata and M. melanoptera D t O 2 were 82.7 ± 17.0% and 85.9 ± 2.5% of the expected value, for C. picui it was only 48.4 ± 18.5% of the expected value.…”

“…In birds, the lung volume is lower than that of non-flying mammals, while bat lungs show the opposite trend. High respiratory surface density and a thin air-blood barrier have been reported in several small bird species, such as Sparkling Violater (Colibri coruscans) (Dubach, 1981) while the Orders containing non-flying birds or birds that fly occasionally (e.g., Sphenisciformes, and Galliformes or Struthioformes), appear to have a thicker blood-gas barrier than flying birds (Maina, 2002;Canals et al, 2007;Figueroa et al).…”

“…Regarding doves and pigeons, high oxygen diffusion capacity in Columba libia (Maina, 2000) and Zenaida auriculata have been reported, which in the latter species is also associated with smaller red blood cells than the cursorial species Nothoprocta perdicaria (Chilean Tinamu) (Canals et al, 2007;Figueroa et al). One might expect then that species of pigeons with increased energy requirements such as those living in high altitudes or with very small body size, would have high oxygen diffusion capacities.…”

The Evolution of Unidirectional Pulmonary Airflow

“…This capacity can be quantified morphologically by measuring the ratio of the diffusive surface area of the lung and the harmonic mean thickness of the blood-gas barrier, the anatomical diffusion factor (ADF). Birds and mammals using the same mode of locomotion have very similar ADF (31,48,60). The power required for locomotor modes such as swimming and running is less than for modes such as flapping flight.…”

Biomechanical, Respiratory and Cardiovascular Adaptations of Bats and the Case of the Small Community of Bats in Chile

“…However, bats have the highest levels of hematocrit measured in mammals and may reach values above 70% in Tadarida brasiliensis and Miniopterus minor. Red blood cells are smaller (Figueroa et al, 2007) and hemoglobin has been found in higher concentrations (18-24 g/100ml blood), similar to that found in hummingbirds (Johansen et al, 1987). Consequently, bats have a transport capacity of oxygen in the blood of 25 to 30%.…”