Circulation and respiratory control in millimetre-sized animals (Daphnia magna, Folsomia candida ) studied by optical methods |
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Authors: | Rüdiger J Paul Michael Colmorgen Stefan Hüller Florian Tyroller Dietmar Zinkler |
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Institution: | Institut für Zoophysiologie, Westf?lische Wilhelms-Universit?t, Hindenburgplatz 55, D-48143 Münster, Germany Tel.: +49-251/8323851, Fax: +49-251/8323876, e-mail: paulr@uni-muenster.de, DE Institut für Zoologie, Ludwig-Maximilians-Universit?t, Luisenstrasse 14, D-80333 München, Germany, DE Lehrstuhl für Tierphysiologie, Ruhr-Universit?t, Universit?tsstrasse 150, D-44780 Bochum, Germany, DE
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Abstract: | During hypoxia, oxyregulating water-breathers usually control O2 uptake by changing ventilatory convection. Using optical techniques we studied ventilation, circulation and respiratory control
in small animals, a millimetre in size, which were more or less pronounced oxyregulators (Daphnia magna, Folsomia candida). In Daphnia we found no adaptive changes in the ventilatory water flow rate during hypoxia. Frequency and amplitude of the movements
of the thoracic limbs remained constant during this environmental condition. During anoxia there was a reduction in both.
In contrast to ventilatory convection, the circulatory blood flow rate adapted to hypoxia. At low oxygen partial pressures,
the heart frequency strongly increased (compensatory tachycardia) in Daphnia, whereas the stroke volume remained constant. Accordingly, there was an increase in cardiac output during hypoxia. Folsomia also showed a marked increase of heart frequency during severe hypoxia. The adaptive changes in blood flow rate should help
to maintain sufficient partial pressure differences between medium, blood and tissues and should help to avoid anoxic zones
in the animal. During anoxia, the heart continued to beat in Daphnia (at a rate more or less similar to normoxia, but with a reduced stroke volume) for periods of many hours. The heart frequency
showed typical courses during anoxia and subsequent normoxia, which are probably related to energy metabolism.
Accepted: 28 February 1997 |
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Keywords: | Circulation Daphnia Image processing Optophysiology Respiratory control |
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