Western Washington University Western CEDAR Biology Faculty and Staff ubP lications Biology 1-1986 Ventilation, Gas Exchange, and Aerobic Scope in a Small Monitor Lizard, Varanus gilleni Philip E. Bickler Roger A. Anderson Western Washington University, [email protected] Follow this and additional works at: https://cedar.wwu.edu/biology_facpubs Part of the Biology Commons Recommended Citation Bickler, Philip E. and Anderson, Roger A., "Ventilation, Gas Exchange, and Aerobic Scope in a Small Monitor Lizard, Varanus gilleni" (1986). Biology Faculty and Staff Publications. 37. https://cedar.wwu.edu/biology_facpubs/37 This Article is brought to you for free and open access by the Biology at Western CEDAR. It has been accepted for inclusion in Biology Faculty and Staff ubP lications by an authorized administrator of Western CEDAR. For more information, please contact [email protected]. Division of Comparative Physiology and Biochemistry, Society for Integrative and Comparative Biology Ventilation, Gas Exchange, and Aerobic Scope in a Small Monitor Lizard, Varanus gilleni Author(s): Philip E. Bickler and Roger A. Anderson Source: Physiological Zoology, Vol. 59, No. 1 (Jan. - Feb., 1986), pp. 76-83 Published by: The University of Chicago Press. Sponsored by the Division of Comparative Physiology and Biochemistry, Society for Integrative and Comparative Biology Stable URL: http://www.jstor.org/stable/30156093 . Accessed: 20/01/2015 18:36 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The University of Chicago Press and Division of Comparative Physiology and Biochemistry, Society for Integrative and Comparative Biology are collaborating with JSTOR to digitize, preserve and extend access to Physiological Zoology. http://www.jstor.org This content downloaded from 140.160.178.72 on Tue, 20 Jan 2015 18:36:46 PM All use subject to JSTOR Terms and Conditions VENTILATION, GAS EXCHANGE, AND AEROBIC SCOPE IN A SMALL MONITOR LIZARD, VARANUS GILLENI' PHILIPE. BICKLER2'3AND ROGER A. ANDERSON Departmentof Biology,University of California,Los Angeles, Los Angeles, California 90024 (Accepted7/11/85) Standardrates of 02 consumption(Vo2) in the darkof Varanusgilleni (mean mass = 30 g) were measuredat 25, 31, 34, and 37 C. At 37 C, the mean value (195 ml 02 STPDkg-' h-') was 22%lower than that predictedby a regressionequation for lizards as a group (Bennett and Dawson 1976). Despite appearingto be asleep, three- to fourfoldelevations in standardVo2 were seen in lizardswith lightweight,transparent respiratorymasks. Vo2 was also measuredduring treadmill exercise at speedsfrom 5 to 15 m min-' and duringbouts of maximalexercise. Varanusgilleni has the highest factorialaerobic scope (27.5) of any lizardexamined to date. The cost of transportin V.gilleni is relativelyhigh and may relateto shortlimb length. Pulmonaryventilation and gas exchange (VE, V02, VC02)were simultaneouslymeasured at 25 C, during warming from 25 to 35 C, and again after several hours at 35 C. Air-convection requirementsfor CO2and 02 were independentof temperature.The patternsof lung ventilation suggestthat arterialPCo2 and pH are constant with rising temperature, behaviorthat is common to that in large varanidsand in contrast to that in other reptiles. INTRODUCTION standard Vo2 in larger varanids (Bartholo- Lizards of the family Varanidae are gen- mew and Tucker 1964; Wood et al. 1978), erally considered to exceed the capabilities but other measurements of standard Vo2 of lizards of other families in the ability to of large varanids fall on the regression of sustain intense aerobic exercise. The var- body mass and Vo2 of lizards as a group anid characteristics of high hematocrit and (Bennett 1972; Gleeson 1980). efficient 02 uptake from lung gas to blood Lung ventilation in large varanids re- and from blood to tissues correlate with sponds to changes in body temperature in their high aerobic scopes for exercise (Ben- a different way than has been reported for nett 1973; Gleeson 198 1). However, data lizards of other families: the ratio of minute for these generalizations come exclusively volume (VE) to Vo2 is independent of tem- from a few large species (-- I kg; see Gleeson perature (Wood, Glass, and Johansen 1977; 1981). Currently, it is not known whether Wood et al. 1981). This pattern achieves a these functional capabilities are shared by relatively constant 02 extraction efficiency the smaller members of the family. over a range of temperature as well as a The relationships of body size to standard relatively constant lung P02. It has been oxygen consumption (Vo2) and to Vo2 suggested that the relatively constant lung during maximal exertion in varanids is not PO2serves to support 02 delivery to tissues clear. There are several reports of elevated during activity (Wood et al. 1977). These patterns of ventilation may also produce a relatively constant relationship between 'We wouldlike to thankDavid Morafka and Bob lung Pco2 and body temperature. The con- Drewesfor loanof the lizards. was Equipment gen- stant lung PCO2is reflected in temperature- erouslyloaned by G. A. Bartholomew.This work was arterial and hence in rel- supportedby a Chancellor'sPatent Fund Grant to independent Pco2 P.E.B.from UCLA. atively constant arterial pH despite tem- 2 Presentaddress: Physiological Research Labora- perature changes (Wood et al. 1981). tory, ScrippsInstitution of Oceanography,A-004, The present study was done to see Universityof California, San Diego, La Jolla, California whether 92093. some of the physiological features of 3 Orderof authorshipdecided by coin flip. large varanids are shared by one of the smallest members of the family. The lizard Physiol. Zool. 59(1):76-83. 1986. we studied, the pigmy mulga monitor c 1986 by The University of Chicago. All (Varanus gilleni) is small (<0. I kg), secre- rights reserved. 0031-935X/86/5901-4122$02.00 tive, and thigmothermic (i.e., it obtains heat 76 This content downloaded from 140.160.178.72 on Tue, 20 Jan 2015 18:36:46 PM All use subject to JSTOR Terms and Conditions METABOLISM AND VENTILATION IN VARANUS 77 from warmsubstrates) (Pianka 1969). This maintainedat either 25, 31, 34, or 36-37 arborealspecies is found under the barkof C. We weighed the lizards and took their trees in the deserts of central Australia.It cloacaltemperature immediately after each preys principallyon large arthropodsand trial. Rates of oxygen consumption re- small arborealgekkos. Although field-active ported represent the means of values ob- body temperatureshave not been reported tained every 5 min for 2-3 h. The lizards for this species, varanidsof similar ecology appearedto be asleep duringthe entire 2- and bodysize havebody temperatureswhile 3-h period. active of 37-38 C (Pianka 1969). We mea- sured standardVo2, Vo2 during treadmill EXERCISE METABOLISM and maximalexercise, respiratory exchange The lizardswere fasted 2-3 days before ratios, and patternsof pulmonary ventila- exerciseon the treadmill. At the onset of tion at differentbody temperatures. fasting,plastic collarsfor the attachmentof respiratorymasks were glued on to the MATERIAL AND METHODS necks with silicone sealant. Lizards were For 30 days prior to the study in spring then placed in a temperature-controlled 1981, four Varanusgilleni of mass 20-40 cabinet at 35-37 C under the previously g (held in captivity for 1 yr) were kept in established photoperiod. On the day of large glass terrariaunder 12L:12D photo- measurementof V02 duringexercise, clear periods.A 2,000-w photofloodlamp placed plastic masks (snap-capvials) were placed above one end of each terrariumprovided over the head and sealed to the collar. Air light and heat during photophase. Lizards was drawnthrough the masksby the lizards thermoregulatedfreely at a body temper- for the remainderof the day. Flexiblelatex ature (Tb) of - 37 C. At night Tb dropped tubingwas attachedto the mask for routing to ambienttemperature, - 25 C. All lizards of incurrentand excurrentair. The tubes were fed a diet of mealworms,crickets, and were positioned above and in front of the small lizards; water was continuously exercising lizards so that the combined available. weight of the tubing and mask did not in- terferewith locomotion. STANDARD METABOLISM The lizardswere run on a treadmillin a Standardrates of Vo2 (standard meta- 37 C room. All measuresof Vo2 for exer- bolic rate [SMR]) were measured in the cisinglizards were obtainedduring the first dark,during apparent sleeping behavior in half of photophase during a 3-day period. the firsthalf of normal scotophase.The liz- Vo2 was measuredwith the same open-cir- ardswere not fed for 2-3 days beforea trial. cuit systemdescribed for the standardmet- The lizardswere placed unrestrainedin re- abolic rate (SMR) measurements. spiratorychambers 3-4 h before a trial. Each day several treadmill speeds were SMRswere also measuredin lizardstreated usedfor each lizard,the slowestspeed being identically except for being fitted with a used first.Steady V02 values weretypically lightweight,airtight plastic mask fittedwith obtainedafter 3-10 min of running.These inflow