Respiratory and cardiovascular adjustments to exercise in reptiles (original) (raw)
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Aerobic and anaerobic metabolism during activity in the lizard Dipsosaurus dorsalis
J Comp Physiol a, 1972
1. Oxygen consumption and lactate content of the lizard Dipsosaurus dorsalis were determined under standard conditions and for a bout of maximal activity induced by a 2-min period of electrical stimulation. Observations were made between 25 ~ and 45 ~ C. 2. Maximal aerobic scope, 2.27 cm a 02/(g• occurred at 40~ (Figs. 2, 4). The increase in oxygen consumption during activity at the various temperatures between 25 ~ and 45~ represented 7-to 17-fold of corresponding resting levels. 3. Lactate content of resting Dipsosaurus is independent of temperature and averages 0.25 mg/g body weight. Maximal lactate production during the activity induced by a 2-rain period of electrical stimulation occurred at 40~ (Fig. 3). The capacity of Dipsosaurus for anaerobic metabolism exceeds that of other lizards investigated, both in its magnitude and in its thermal dependence. 4. The total amount of energy mobilized by Dipsosaurus in the activity induced by a 2-min period of electrical stimulation was maximal at 40~ (Fig. 4). Anaerobiosis accounts for a minimum of 58-83 % of the total energetic expenditure. 5. It is postulated that the principal physiological adaptations to preferred thermal levels in reptiles have involved energy mobilization during and rapid recovery after activity.
Aerobic and Anaerobic RZetabolism during Activity in the Lizard Dipsosaurus dorsalis
1972
Bnmmary. 1. Oxygen consumption and lactate content of ths lizard Dipsorasvus dorsalis were determined under standard conditions and for s, bout of maximal activity induced by a 2-min period of electricql stimulation. Observations were made between 26' and 45' C.. 2. Maximal aerobic scope, 2.27 cm3 O?/(gxh), occurred at 40' C (Figs. 2, 4). The inin o q g e n consumption during activity at the various temperatures between 25' and 45' C reprcscnted 7-to 17-fold of corresponding resting levels. 3. Lactate content of resting Dipsosaurus is independent of temperature and avenges 025 mg/g body weight. Xaximal lactate production during the activity induced by a 2-min period of electrical sti~nulation occurred a t 40° C (Fig. 3). The capacity of Dipsosaurus for anaerobic metabolism exceeds that of other lizards investigated, both in its magnitude and in its thermal dependence. 4. The total amouuL of euci-gy mobilized by Dip8osaurus in the nctivity induced by a Zmin period of electrical stimulation \\-as maximal a t 40° C (Fig. 4). Anaerobiosis accounts for a minimum of 58-S3?A of the total energetic expenditure. 5. It It. postulated that the principal physiological adaptations to preferred thermal levels in reptiles have in~olved energy mobilization during and rapid recovery after activity.
Journal of Comparative Physiology, 1972
Oxygen consumption and heart rate were measured during rest and activity in the lizards Varanus gouldii and Sauromalus hispidus. Oxygen debt was calculated from postactive oxygen consumption. Standard metabolic rates of the two animals are similar but Varanus consumes much more oxygen during activity than does Sauromalus (Fig. 1-3). The latter has a constant active metabolic rate above 30~ and accumulates a large oxygen debt, which is repayed slowly (Fig. 4). Varanus recovers rapidly from activity (Fig. 5), presumably because of the smaller lactacid debt incurred. Heart rate increment in Sauromalus is high (Fig. 8). This variable cannot be responsible for the limitation of active oxygen consumption; calculations of oxygen pulse suggest that an inability to increase A-V difference and/or stroke volume are implicated (Fig. 9). Varanu~ have evolved mechanisms to sustain high levels of oxygen consumption superior to those of other reptiles investigated. The role of anaerobiosis in the biology of both animals is discussed.
Effects of endurance training and captivity on activity metabolism of lizards
The American journal of physiology, 1987
Two groups of Amphibolurus nuchalis, an Australian agamid lizard, were maintained in captivity for 8 wk. The "trained" group was given submaximal exercise at 1 km/h on a motorized treadmill, 30 min/day, 5 days/wk; the treadmill was inclined 10% for the last 5 wk. The "sedentary" group was not exercised. Endurance capacity did not change significantly in either group, but sprint speed decreased in trained lizards. The sedentary group exhibited significant decreases in maximal O2 consumption, standard metabolic rate, and heart mass, but an increase in liver mass. Trained lizards exhibited significant decreases in heart and thigh muscle masses, but significant increases in liver mass, hematocrit, liver pyruvate kinase, and heart citrate synthase activities. It is concluded that the adaptive response to endurance training, typical of mammals, does not generally occur in lizards. Moreover, levels of chronic activity that would elicit adaptive responses in mammals may ...
ACTIVITY METABOLISM IN THE LIZARD SCELOPORUS OCCIDENTALIS
2000
Standard levels of oxygen consumption and oxygen consumption and lactate production during and after burst activity were measured in the iguanid lizard Scelopmus occidentalis. The activity capacity of this animal is restricted; it sustains vigorous movement for only 1-2 min. The contribution of aerobic metabolism to that activity is strongly thermally dependent. Maximal levels of oxygen consumption are achieved during activity a t 3 0 4 0 C. At lower temperatures, significant lags occur in oxygen uptake, which appear to result from restricted ventilation. The maximum aerobic increase above resting levels occurs a t 35 C, preferred body temperature of this species. Repayment of the initial stages of oxygen debt is also most rapid a t 35 C.
Comparative biochemistry and physiology. A, Comparative physiology, 1973
Aspects of blood physiology-hematocrit, oxygen capacity and affinity, lactate content, pH and composition of blood buffers-were investigated in the lizards Varanus got&z% and Sauromalus hispidus during activity at different temperatures. 2. Although oxygen capacity and affinity, resting pH and lactate levels, bicarbonate and phosphate concentrations are nearly identical in both species, only Sauromalus sustains a decrease in blood pH during activity, accompanied by a decrease in oxygen capacity and afhnity, high levels of lactate production and exhaustion. 3. Non-carbonic blood buffers prevent a change in blood pH in Vurunus. Lungs of great surface area facilitate exchange of oxygen and carbon dioxide, and Varanus undergoes only moderate lactate generation and remains aerobic during activity. ALBERT F. BENNETT levels of oxygen consumption are, however, identical to those of other reptiles of equal size (Bennett, 1972b). S ince maintenance costs are equal, it appears that Vuvanus possesses specific capabilities for sustained oxygen utilization during activity which other lizards lack. An extensive study (Bennett, 1971) was undertaken to determine how varanid lizards are able to function aerobically in contrast to other anaerobic saurians. Previously published portions of that study (Bennett, 1972a, b, 1973) have indicated a lack of specialization in the ventilatory, circulatory or enzymatic systems, suggesting that the blood physiology of varanids may be responsible for their greater oxygen transporting capacity. For instance, a greater blood oxygen capacity or affinity might account for the difference. This study reports measurements of hematocrit and oxygen capacity of the sand goanna, Varanus gouldii, and an iguanid lizard, the spiny chuckwalla, Sauromalus hispidus, animals of equal size (approximately 0.5 kg) and thermal preferendum (37-38°C). The effects of activity on blood pH, lactate content and oxygen affinity are also examined, as well as measurements of the blood buffering capacity and composition of both animals. Experimental animals MATERIALS AND METHODS Fifteen adult S. hispidus (mean weight, 574 g) and ten adult V. gouldii (mean weight, 674 g) were used in these experiments. Conditions of animal maintenance have been described elsewhere (Bennett, 1972b). Experiments were run on Varanus in February-March and on Saurmlus in June-July, the summer active period for both species. All animals were fasted at least 2 days before experimentation.
Ventilation and acid-base balance during graded activity in lizards
The American journal of physiology, 1981
Arterial PCO2, hydrogen ion ([H+]a), and lactate ([L]a) concentrations, rates of metabolic CO2 production (VCO2) and O2 consumption (VO2), and effective alveolar ventilation (Veff) were determined in the lizards Varanus exanthematicus and Iguana iguana at rest and during steady-state treadmill exercise at 35 degrees C. In Varanus, VCO2 increased ninefold and VO2 sixfold without detectable rise in [L]a at running speeds below 1.0 to 1.5 km x h-1. In this range, Veff increased 12-fold resulting in decreased levels of PaCO2 and [H+]a. At higher speeds [L]a rose. Increments of 5 mM [L]a were accompanied by hyperventilation, reducing PaCO2 and thus maintaining [H+]a near its resting level. When [L]a increased further, [H+]a increased. Sustainable running speeds (0.3-0.5 km x h-1 and below) were often associated with increased VO2, VCO2, and [L]a in Iguana. Sixfold increases in VCO2 and 9-mM increments in [L]a were accompanied by sufficient increase in Veff (9-fold) to maintain [H+]a at o...