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Journal of Experimental Biology 123,27-41 (1986)
Published by Company of Biologists 1986

Effective and Morphometric Oxygen-Diffusing Capacity of the Gills of the Elasmobranch Scyliorhinus Stellaris

JOHANNES PIIPER 1, PETER SCHEID 2, STEVEN F. PERRY 3, and GEORGE M. HUGHES 4

1 Abteilung Physiologie, Max-Planck-Institut für experimentelle Medizin, Güttingen, FRG
2 Institut für Physiologie, Ruhr-Universität, Bochum, FRG
3 Abteilung Physiologie, Max-Planck-Institut für experimentelle Medizin, Göttingen, FRG; Fachbereich 7 (Biologie) der Universität Oldenburg, 2900 Oldenburg, FRG
4 Research Unit for Comparative Animal Respiration, Bristol University, Bristol, UK

Calculations of the effective O2 conductance (diffusing capacity or transfer factor, Dcff) of fish gills, obtained from experimental data on gill O2 exchange, were compared with the predicted CVexchange properties of gill models based on morphometric measurements of the elasmobranch, Scyliorhinus stellaris. Deff was calculated from O2 uptake and POO2 in gill water and blood, using a modified Bohr integration technique. In the morphometric gill model, O2 conductance was considered for both the water-blood tissue barrier (Dm) and the interlamellar water (Dw). Dm was calculated from the total secondary lamellar surface area, the harmonic mean water-blood barrier thickness, and an assumed Krogh 02-diffusionconstant for gill tissue. Dw was estimated from the dimensions of the interlamellar spaces, the mean respiratory water flow velocity, and the diffusion coefficient of O2 in water.

The ratio Dm/Dw was 1.84 in quiescently resting, 1.68 in resting alert, and 1.47 in swimming fish, showing that diffusion across interlamellar water was somewhat more important than that across the water-blood barrier in limiting the diffusive O2 transfer between water and blood. The total morphometric diffusing capacity, Dmorph estimated by the combined membrane-and-water diffusing capacity, Dm+w, which is defined as 1/Dm+w= 1/Dm+1/Dw, was similar to Deff, the ratio Dm+w/Deff being 1.64 for quiescently resting, 1.02 for resting alert, and 0.92 for swimming fish. The good agreement between the effective and morphometric D estimates validates the approach, and leaves, at least for the alert and swimming fish, little space for functional inhomogeneities, which are expected to reduce Deff as compared to Dm+w.

Key words: fishes, elasmobranchs, diffusing capacity for O2, gills, diffusion, morphometry

Submitted on January 23, 1986


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© The Company of Biologists Ltd 1986