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Title: Breathing and gas exchange in an aquatic amphibian, Xenopus laevis
Author: Brett, S. S.
ISNI:       0000 0001 3478 9685
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 1980
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Breathing patterns and ventilatory mechanisms plus oxygen regulation have been investigated in the aquatic anuran Xenopus laevis. Xenopus often surfaces to breath air, but air-breathing bouts are intermittent and apnoeic periods are variable in length, which results in large internal P02 variations. More air breaths occur after longer apnoeic periods, and animals breathe less air under aerial hyperoxic conditions. Aerial hypoxia causes increases in breathing frequency and increases in the volume of air inhaled and exhaled. Also reduced 02 availability in the water has no effect on total 02 consumption, suggesting that 02 regulation is involved in respiratory control. However, control of internal PO2 levels is not precise and 02 regulation must be only part of a complex regulating system of respiration. 02 receptors might be located in the carotid labyrinth of Xenopus, as this area has some of the necessary cardiovascular, structural, and neural elements for such a function. Larger animals take larger air breaths and larger animals also inspire and expire more gas per unit time than do smaller animals. The increases in gas exchanged are larger than would be expected from a direct examination of increases in body weight, Xenopus always exhales less gas than it inhales, because gas exchange also occurs in the cutaneous circulation, but so far as 02 exchange is concerned, the skin is not important and contributes less than 20% to total 02 consumption. Cutaneous 02 exchange is not actively regulated and external aquatic P02 levels have no observable effect on internal 02 levels. Air breaths are usually of an exhalation-inhalation-inhalation pattern, and Xenopus utilises a buccal force pump for ventilation but, unlike other anurans, expiration always precedes inspiration in Xenopus and muscles which act to oecrease the volume of the buccal cavity are active to more completely empty the buccal chamber. Flank muscles and specialised lung muscles are consistently active during expiration and inhalation of air into the buccal cavity, and this may aid ventilation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Zoology