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First published online March 9, 2004
Journal of Experimental Biology 207, 1305-1311 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00882

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Independent effects of heart–head distance and caudal blood pooling on blood pressure regulation in aquatic and terrestrial snakes

Roger S. Seymour^1,* and Joachim O. Arndt²

¹ Environmental Biology, University of Adelaide, Adelaide, SA 5005, Australia
² Department of Experimental Anaesthesiology, Heinrich-Heine-Universität, Universitätsstrasse 1, 40225 Düsseldorf, Germany

View larger version (23K): [in a new window]   Fig. 1. Apparatus to tilt snakes about the heart, either partially or fully. The animal is restrained in two acrylic tubes and a hosiery sleeve (not shown).

View larger version (40K): [in a new window]   Fig. 2. An example of the patterns of blood pressure and heart rate of a python (Liasis fuscus) associated with head-up, straight tilts to either 30° or 70°. Blood pressures at heart level in the central aorta (CAP) and central post caval vein (CVP) and heart rate (HR; beats min–1) are shown.

View larger version (32K): [in a new window]   Fig. 3. An example of the patterns of blood pressure of file snakes (Acrochordus arafurae) associated with head-up, straight tilts to 30°, 45° or 70°. Blood pressures at heart level in the central aorta (CAP) and central post-caval vein (CVP) are shown. CVP was measured below the heart but adjusted to heart level, causing apparent negative values.

View larger version (21K): [in a new window]   Fig. 4. Means (± 95% confidence intervals) of central arterial blood pressures at the heart in five pythons (Liasis fuscus; filled symbols) and six file snakes (Acrochordus arafurae; open symbols) near the end of 2 min partial (head-up and tail-down) and full tilts. Some angles shifted slightly for clarity.

View larger version (22K): [in a new window]   Fig. 5. Means (± 95% confidence intervals) of calculated arterial blood pressures at head level in five pythons (Liasis fuscus; filled symbols) and six file snakes (Acrochordus arafurae; open symbols) near the end of 2 min partial (head-up and tail-down) and full tilts. Negative values (blue area) are calculated.

View larger version (21K): [in a new window]   Fig. 6. Means (± 95% confidence intervals) of central venous blood pressures at the heart in five pythons (Liasis fuscus; filled symbols) and six file snakes (Acrochordus arafurae; open symbols) near the end of 2 min partial (head-up and tail-down) and full tilts. Negative values (blue area) are calculated.

View larger version (20K): [in a new window]   Fig. 7. Means (± 95% confidence intervals) of heart rates at the heart in five pythons (Liasis fuscus; filled symbols) and six file snakes (Acrochordus arafurae; open symbols) near the end of 2 min partial (head-up and tail-down) and full tilts.

View larger version (17K): [in a new window]   Fig. 8. Effect of full and partial tilting to 45° on blood pressures in the python (Liasis fuscus). Means ± 95% confidence intervals represent head arterial pressure (HAP), central arterial pressure at the heart (CAP) and central venous pressure at the heart (CVP).

View larger version (17K): [in a new window]   Fig. 9. Effect of full and partial tilting to 45° on blood pressures in the file snake (Acrochordus arafurae). Means ± 95% confidence intervals represent head arterial pressure (HAP), central arterial pressure at the heart (CAP) and central venous pressure at the heart (CVP).