Abstract
The tokay lizard (Gekko gecko) possesses singlechambered lungs, eacch of which is a mirror image of the other reflected in the midsagittal body plane. When standard techniques are employed for instilling 2% phosphate-buffered glutaraldehyde to three-quarters of the total lung capacity, neither the left nor the right lung is consistently larger. Internally, the lungs are characterized by a row of 11 dorsomedial niches and by honeycomb-like (faveolar) gas exchange tissue, which is deeper cranially than caudally. Based upon mean values for all experimental animals, a 100-g tokay would have an overall anatomical diffusion factor (respiratory surface area divided by the appropriate τht) of 203 cm2·μm-1·100 g-1, 61% of which is located on the interfaveolar septa. Of the total septal anatomical diffusion factor, 94% is evenly divided between the anterior and middle thirds of the lung, with 6% in the posterior third. The 39% of the anatomical diffusion factor located on the inner lung wall is predominantly (76%) in the middle and posterior lung thirds, with only 24% in the anterior region. These tendencies toward heterogeneous distribution of anatomical diffusion factor were most pronounced in a 55 g juvenile animal. In this animal the total anatomical diffusion faxtor/body mass was 3.6 times that of a 197 g adult. This difference was attributable to a greater body massspecific lung volume and respiratory surface area as well as to a greater surface-to-volume ratio in the parenchyma and to a thinner air-blood diffusion barrier in the juvenile animal.
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Abbreviations
- ADF:
-
anatomical diffusion factor
- %AR:
-
percentage of potential respiratory surface area which makes up SAR
- DtO2 :
-
diffusing capacity for air-blood tissue barrier
- IUR:
-
isotropic uniform randomly distributed
- bm:
-
body mass
- %P :
-
percentage of lung volume devoted to parenchyma
- S A :
-
potential respiratory surface area (S L minus the surface area of the trabeculae)
- S ANR :
-
non-respiratory surface area
- S AR :
-
respiratory surface area
- S L :
-
total internal surface area of the lung
- S v :
-
surface area-to-volume ratio in parenchyma
- τht :
-
harmonic mean thickness of the air-blood tissue barrier
- V L :
-
morphometrically determined volume of both lungs, fixed at 0.75· V Lm
- V Lm :
-
maximal lung volume, similar to total lung capacity in mammals
- V Lr :
-
resting lung volume, similar to functional residual capacity in mammals
- VP:
-
morphometrically determined volume of parenchyma of both lungs, fixed at three-quarters of VLm
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Perry, S.F., Hein, J. & van Dieken, E. Gas exchange morphometry of the lungs of the tokay, Gekko gecko L. (Reptilia: Squamata: Gekkonidae). J Comp Physiol B 164, 206–214 (1994). https://doi.org/10.1007/BF00354081
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DOI: https://doi.org/10.1007/BF00354081