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  • 1
    Electronic Resource
    Electronic Resource
    Population density and energetics of lizards on a tropical island (1979)
    Springer
    Oecologia 42 (1979), S. 339-358 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Population density, biomass, thermal relations and energetics of three common species of lizards (Anolis bonairensis, Cnemidophorus murinus, Gonatodes antillensis) were measured in a thornscrub community on the arid Caribbean island of Bonaire. 2. Population density and biomass estimates of these populations were 1318, 561, and 4200 individuals/ha and 4.2, 15.4, and 3.5 kg/ha, respectively. Although these densities are not exceptional for other Carribbean islands, they greatly exceed lizard densities reported for mainland communities. 3. Mean diurnal body temperatures are 33.4° C for Anolis, 40.4° C for Cnemidophorus, and 34.5° C for Gonatodes. Nocturnal temperatures average 27° C for all species. 4. Resting rates of oxygen consumption for all species were measured at naturally experienced diurnal and nocturnal temperatures. The values were used to calculate Minimal and more realistic Field Active estimates of the respiratory energy utilization of these lizard populations. 5. Minimal estimates of energy expenditure are 326, 950, and 268 kJ/(haxday) for Anolis, Cnemidophorus, and Gonatodes, and Field Active estimates are 693, 2510, and 379 kJ/(haxday), respectively. 6. These estimates greatly exceed values previously reported for other lizard populations. They also exceed reported values for the respiratory metabolism of populations of small mammals in temperate regions. 7. These values are probably not atypical of other tropical insular lizard populations, and the significance of these animals to energy flow in these communities has not generally been appreciated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346598
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of activity on oxygen consumption, oxygen debt, and heart rate in the lizardsVaranus gouldii andsauromalus hispidus (1972)
    Springer
    Journal of comparative physiology 79 (1972), S. 259-280 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Oxygen consumption and heart rate were measured during rest and activity in the lizardsVaranus gouldii andSauromalus hispidus. Oxygen debt was calculated from postactive oxygen consumption. Standard metabolic rates of the two animals are similar butVaranus consumes much more oxygen during activity than doesSauromalus (Fig. 1–3). The latter has a constant active metabolic rate above 30 ° C 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 inSauromalus 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).Varanus 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694220
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  • 3
    Electronic Resource
    Electronic Resource
    Anaerobic metabolism during activity in lizards (1972)
    Springer
    Journal of comparative physiology 81 (1972), S. 277-288 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A new technique developed for the determination of total lactate production in small animals was used to evaluate the role of anaerobiosis during activity at different temperatures in lizards. Measurements on six species of small lizards indicate little interspecific variation or thermal effect in resting lactate levels (0.35 mg lactate/g body weight) or maximal lactate levels achieved at exhaustion (1.4 mg lactate/g). Normally activeAnolis in captivity had a lactate content of 0.5 mg lactate/g. Rates of lactate formation were most rapid during the first 30 sec of activity and had a low thermal dependence (Q10=1.1–1.3 above 20 °C). The lactate formed during activity persists for long periods; e.g., for 30 to 60 min between 20 and 37 °C inAnolis carolinensis (Fig. 1). Recovery rate generally increases with temperature. Muscle lactate concentrations peak at the end of activity, but liver and blood lactate are not maximal until 10 and 30 min, respectively, after activity (Fig. 2). The decrease in the blood lactate is shown to be a poor estimator of total recovery. An estimated 80–90% of the total energy utilized during initial vigorous activity comes from anaerobic sources. Because of its low thermal dependence, anaerobiosis permits high levels of activity in lizards at all body temperatures without requiring high levels of aerobic resting metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693632
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  • 4
    Electronic Resource
    Electronic Resource
    Aerobic and anaerobic metabolism during activity in the lizardDipsosaurus dorsalis (1972)
    Springer
    Journal of comparative physiology 81 (1972), S. 289-299 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Oxygen consumption and lactate content of the lizardDipsosaurus 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 cm3 O2/(g × hr), occurred at 40 °C (Figs. 2, 4). The increase in oxygen consumption during activity at the various temperatures between 25 ° and 45 °C represented 7- to 17-fold of corresponding resting levels. 3. Lactate content of restingDipsosaurus is independent of temperature and averages 0.25 mg/g body weight. Maximal lactate production during the activity induced by a 2-min period of electrical stimulation occurred at 40 °C (Fig. 3). The capacity ofDipsosaurus 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 byDipsosaurus in the activity induced by a 2-min period of electrical stimulation was maximal at 40 °C (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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693633
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  • 5
    Electronic Resource
    Electronic Resource
    Relative contributions of anaerobic and aerobic energy production during activity in amphibia (1973)
    Springer
    Journal of comparative physiology 87 (1973), S. 351-360 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Measurements of oxygen consumption and lactate production during activity were made in three species of amphibians. Oxygen debts and rates of lactate removal were also studied. 2. Maximal values of oxygen consumption are 200 and 500% above resting levels in the plethodontid salamanderBatrachoseps attenuatus and the frogHyla regilla, respectively (Kg. 1). However, these values are not attained until 5–15 min after the cessation of activity. 3. Batrachoseps, a lungless animal, derives 25 times more energy during 2 min of activity from lactate production than from oxygen consumption.Hyla is also predominantly anaerobic during activity butBufo boreas is mainly aerobic. 4. An inverse relationship exists between aerobic and anaerobic scopes in amphibians, such that total energetic output during activity is similar even though the component factors may differ by ten-fold. 5. Oxygen debts inHyla andBatrachoseps after 2-min activity are repayed in approximately one hour but rates of lactate removal are much lower (Fig. 2); large amounts of lactate persist long after oxygen consumption has returned to resting levels. Oxygen debt, therefore, cannot be used as an estimate of energetic expenditure during activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695269
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of body temperature on the locomotory energetics of lizards (1984)
    Springer
    Journal of comparative physiology 155 (1984), S. 21-27 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Oxygen consumption ( $$\dot V_{O_2 } $$ ), carbon dioxide production ( $$\dot V_{CO_2 } $$ ), and stamina were measured in the lizardTupinambis nigropunctatus running at sustainable and non-sustainable velocities (v) on a motor-driven treadmill. Three experimental groups were measured: field-fresh animals at body temperature (T b)=35°C and laboratorymaintained animals atT b=35 and 25 °C. 2. Mean preferredT b was determined to be 35.2 °C. 3. At 35 °C, field-fresh animals had a greater maximal oxygen consumption ( $$\dot V_{O_{2 } max corr} $$ ) (4.22 vs 3.60 ml O2 g−0.76 h−1) and a greater endurance. The net cost of transport (slope of $$\dot V_{O_2 } v^{ - 1} $$ onv) did not differ between the groups (=2.60 ml O2 g−0.76 km−1). Velocity at which $$\dot V_{O_{2\max } } $$ is attained (MAS) is 0.84 km h−1. The respiratory exchange ratio (R) exceeded 1.0 atv above MAS, indicating supplementary anaerobic metabolism. 4. At 25 °C, $$\dot V_{O_{2 } max corr} $$ was lower (2.34 ml O2 g−0.76 h−1) as was endurance, MAS occurring at 0.5 km h−1. Net cost of transport was not significantly different than at 35 °C. 5. The effect ofT b on locomotory costs was analyzed for this lizard and other species. It was concluded that the net cost of transport is temperature independent in all species examined and the total cost of locomotion $$\dot V_{O_2 } v^{ - 1} $$ is temperature dependent inTupinambis (Q10=1.4–2.0) and all other species examined except one. The energetic cost of locomotion [( $$\dot V_{O_2 active} - \dot V_{O_2 rest} $$ )v −1], previously reported to be temperature independent in lizards, is temperature dependent inTupinambis (Q10=1.3–1.6) and in two other species. 6. Previous work has interpreted the energetic cost of locomotion as reflecting thermally independent costs of muscle force generation in vivo. These conclusions are questioned on both their generality and their practical and theoretical bases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00688787
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal dependence of isotonic contractile properties of skeletal muscle and sprint performance of the lizardDipsosaurus dorsalis (1985)
    Springer
    Journal of comparative physiology 155 (1985), S. 541-551 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Contractile properties of the fasttwitch glycolytic (FG) portion of the iliofibularis muslce and sprint running performance were studied at approximately 5°C intervals from 15–44°C in the lizardDipsosaurus dorsalis. 2. Maximal running velocity (VR) and stride frequency (f) were both greatest when body temperature (T b) was 40°C, the field-active,T b inDipsosaurus. At 40°C VR was 4.3±0.2 m/s and f was 13.5±0.5 s−1. 3. Between 25 and 40°C, the thermal dependencies of VR and f were approximately constant (Q10's of 1.31 and 1.36 for VR and f, respectively). Below 25°C performance declined more markedly with decreasing temperature. At 20°C strides were qualitatively normal, but VR was only half of the value at 25°C. At 15°C the lizards were substantially incapacitated, and VR was 10% of the value at 20°C. Stride length was approximately 0.33m and changed very little withT b from 20–44°C. 4. The time dependent contractile properties of FG muscle were affected more by temperature than was sprint performance. The maximal velocity of shortening at zero load (Vo) was 18.7 l0/s at 40°C and had a Q10 of 1.7 from 25–40°C. Maximal power output ( $$\dot W_{max} $$ ) determined from the forcevelocity curve was 464 W/kg at 40°C. Below 40°C $$\dot W_{max} $$ varied with temperature with a Q10 of 2–3. The shape of the force-velocity curve changed little with temperature ( $$\dot W_{max} $$ /POVO=0.11). 5. Between 25 and 40°C a relatively temperature-independent process must modulate the effects of temperature on the contractile properties of the muscles that supply the power for burst locomotion. Storage and recovery of elastic energy appears to be a likely candidate for such a process. 6. Below 25°C, however, the contraction time is prolonged to such an extent that the f attainable is limited by the minimum time taken to contract and relax the muscles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00694443
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  • 8
    Electronic Resource
    Electronic Resource
    Physiological correlates of natural activity and locomotor capacity in two species of lacertid lizards (1984)
    Springer
    Journal of comparative physiology 154 (1984), S. 113-118 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Physiological factors relating to activity metabolism were measured in two species of African lacertid lizards that differ greatly in natural foraging patterns:Eremias lineoocellata, a sit-and-wait predator, andE. lugubris, a widely foraging animal. 2. Maximal oxygen consumption at 37°C is greater inE. lugubris [3.22 ml O2/(gxh)] than inE. lineoocellata [2.49 ml O2/(gxh)]. 3. Anaerobic scope and capacity at 37°C are greater inE. lineoocellata [2.56 mg lactate/(gx min) and 1.81 mg lactate/g] than inE. lugubris [2.12 mg lactate/(gxmin) and 1.40 mg lactate/g]. 4. Relative heart mass and hematocrit are greater inE. lugubris than inE. lineoocellata (0.28% and 0.24% body mass; 30.1 and 24.4 respectively). 5. No significant interspecific differences occur in hind limb muscle mass as a percentage of body mass or in myoglobin concentration, citrate synthase or myofibrillar ATPase activity of hind limb skeletal muscle. 6. No significant interspecific differences occur in isometric contractile properties (twitch and tetanic tension, twitch rise time and half-relaxation time, and fatigue response to tetanic stimulation) of the iliofibularis muscle. 7. Organismal metabolic patterns of aerobic and anaerobic capacity reflect differences in locomotor capacity and natural foraging patterns of these species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00684134
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal adaptations in lizard muscle function (1987)
    Springer
    Journal of comparative physiology 157 (1987), S. 241-252 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This study was undertaken to investigate thermal adaptations in muscle contractile properties in closely-related lizards with different preferred body temperatures (PBT). The species examined all belong to theSphenomorphus group of Australian skinks (Scincidae: Lygosominae). Preferred body temperatures are conservative at the generic level as follows:Ctenotus, 35°C;Sphenomorphus, 30°C;Eremiascincus, 25°C. Contractile properties of the fast glycolytic portion of the iliofibularis muscle were measured. Translational adaptations are evident in several isometric factors, including tetanic tension (Po), twitch tension (Pt), twitch time to peak tension (TPT), and twitch half-relaxation time (1/2 RT). Capacity adaptations are not evident in rates of tetanic tension development (dPo/dt) or in maximal velocities of isotonic shortening (V max). Rotational adaptations are not evident in any contractile properties. Thermal limits on upper response temperatures are about 5°C warmer inCtenotus than in the more cryophilic species, indicative of resistance adaptation in muscle performance. Despite these adaptive shifts, there is little indication that muscle functional capacities are optimized or equalized at PBT in these lizards.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692369
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal dependence of locomotory energetics and aerobic capacity of the Gila monster (Heloderma suspectum) (1983)
    Springer
    Journal of comparative physiology 151 (1983), S. 119-126 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The thermal dependencies of sustainable locomotion and aerobic energetics were determined in the Gila monster, a lizard of relatively low thermal preference. Maximal aerobic speed (MAS) is 0.70 km/h at 25°C and 1.03 km/h at 35°C (Q10=1.5). Endurance declines as speed is increased above MAS, and Gila monsters are unusual in being unable to engage in brief periods of high-speed burst locomotion. The rate of O2 consumption ( $$\dot V_{O_2 } $$ ) during locomotion has the same thermal dependence as that of MAS. Maximal $$\dot V_{O_2 } $$ 's are 0.594 ml O2/(g·h) at 25°C and 0.896 ml O2/(g·h) at 35°C (Q10=1.5). The masscorrected $$\dot V_{O_2 } $$ max of the Gila monsters is highest among lizards at 25°C and is relatively high, consistent with other platynotans, among lizards at 35°C. Net cost of locomotion is temperature independent and is relatively low among lizards. Low net cost of locomotion together with high $$\dot V_{O_2 } $$ max's lead to Gila monsters having high MAS's at both 25°C and 35°C. Gila monsters thus appear to be well adapted for aerobic, sustainable activity. The total cost of locomotion shows a positive thermal dependence. However, the minimum cost of transport, attained at the highest sustainable speed, is temperature independent. Locomotion at MAS becomes faster with increasing body temperature with no obligatory increase in total cost of locomotion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689909
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