Oxygen pressures in haemolymph and various tissues of the tarantula,Eurypelma helluo

Abstract

By means of Pt-microelectrodes, oxygen pressure was measured in the haemolymph and in various tissues of the tarantula,Eurypelma helluo. 1. In resting, restrained animals, the arterialpO2 obtained in the heart is 31 Torr. The venouspO2 in haemolymph of the thir femur is 9.7 Torr. The same pressure was found in the haemolymph of the metatarsus. 2. Tissue oxygen pressures were measured in the dorsal region of the opisthosoma (comprising gut diverticula, pericardium, and heart), in the head region of the prosoma, and in the femur. The oxygen profiles obtained by advancing the electrode in 20–40 μ increments are reproducible and characteristic of each region. Inside the muscles the lowest pressures were 1–3 Torr (heart wall), 4–10 Torr (muscles of the prosoma), and 1–4 Torr (femur muscle). ThepO2 gradient between haemolymph and tissues is approximately 13 Torr/100 μ in the heart wall, 7 Torr/100 μ in muscles of the prosoma, and 3 Torr/100 μ in femur muscle. 3. The frequency distribution of tissuepO2 shows peaks far below venous oxygen pressure indicating longer diffusion paths than in vertebrate tissues. 4. In undiluted haemolymph theP 50 of the haemocyanin is 3 Torr at 25°C and pH 8.14. Cell-free haemolyph samples drawn from the heart and femur had an average pH of 8.08 and 8.09, respectively, at 22°C. Under these conditions the haemocyanin is completely saturated in the arterial blood, and 88% saturated in venous blood. 5. The haemocyanin ofEurypelma shows a strong Bohr effect (ΔlogP 50/ΔpH=−0.52 between pH 7.27 and 8.24, and −1.2 at haemolymph pH). In resting, restrained animals, the arterialpO2 obtained in the heart is 31 Torr. The venouspO2 in haemolymph of the thir femur is 9.7 Torr. The same pressure was found in the haemolymph of the metatarsus. Tissue oxygen pressures were measured in the dorsal region of the opisthosoma (comprising gut diverticula, pericardium, and heart), in the head region of the prosoma, and in the femur. The oxygen profiles obtained by advancing the electrode in 20–40 μ increments are reproducible and characteristic of each region. Inside the muscles the lowest pressures were 1–3 Torr (heart wall), 4–10 Torr (muscles of the prosoma), and 1–4 Torr (femur muscle). ThepO2 gradient between haemolymph and tissues is approximately 13 Torr/100 μ in the heart wall, 7 Torr/100 μ in muscles of the prosoma, and 3 Torr/100 μ in femur muscle. The frequency distribution of tissuepO2 shows peaks far below venous oxygen pressure indicating longer diffusion paths than in vertebrate tissues. In undiluted haemolymph theP 50 of the haemocyanin is 3 Torr at 25°C and pH 8.14. Cell-free haemolyph samples drawn from the heart and femur had an average pH of 8.08 and 8.09, respectively, at 22°C. Under these conditions the haemocyanin is completely saturated in the arterial blood, and 88% saturated in venous blood. The haemocyanin ofEurypelma shows a strong Bohr effect (ΔlogP 50/ΔpH=−0.52 between pH 7.27 and 8.24, and −1.2 at haemolymph pH).

DOI: 10.1007/BF00706124

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Cite this paper

@article{Angersbach2004OxygenPI, title={Oxygen pressures in haemolymph and various tissues of the tarantula,Eurypelma helluo}, author={Dieter Angersbach}, journal={Journal of comparative physiology}, year={2004}, volume={98}, pages={133-145} }