Journal of J Comp Physiol B (1984) 154:311-316 Comparative Systemle,Bi~ and Environ- Physiology B m..,.,Physiology Springer-Verfag 1984

The influence of temperature, sexual condition, and season on the metabolic rate of the hispanicus

J.W. Patterson* and P.M.C. Davies Department of Zoology, University of Nottingham, Nottingham NG7 2RD, United Kingdom

Accepted October 27, 1983

Summary. Male and female Psammodromus because most of the used were aquatic; hispanicus from southern Europe were acclimated in aquatic habitats the temperature of the water, to four seasonal conditions of photoperiod and and therefore the body temperature of the aquatic night time temperature. During the dark period, ectotherm, changes slowly with season. Most the ' body temperatures fell to ambient air aquatic organisms investigated in this way show temperature but during the light period the lizards a pattern of Precht type 2 (perfect) or type 3 (par- were allowed to thermoregulate behaviourally, and tial) acclimation (see Fry and Hochachka 1970; at such times the lizards' mean body temperature Vernberg and Vernberg 1970; Hazel and Prosser varied from 29.0 ~ to 32.6 ~ The resting meta- 1974). Thus, following a temperature change in the bolic rate of these lizards was measured in 5 ~ environment, most aquatic animals respond by ad- steps from 5 ~ to 30 ~ or 35 ~ Sexual condition justing their metabolic rate so that it is brought had little effect on resting metabolic rate, but at back to or near its original level. In these circum- low temperatures lizards acclimated to winter or stances, thermal acclimation serves to maintain spring seasonal conditions had lower resting meta- metabolic rate moderately constant over a range bolic rates than those acclimated to summer or of slowly-changing body temperatures. Exposure autumn conditions. At temperatures above 20 ~ to constant temperatures followed by measure- seasonal acclimation had no effect on resting meta- ments of metabolic rate at different temperatures bolic rate. It is considered that the reduction in has also been used as a method to determine the low temperature metabolic rate in spring and acclimatory responses of terrestrial ectotherms, in- winter is induced by low night time temperatures cluding (Gelineo 1965; Murrish and Vance and serves to conserve energy during those seasons 1968; Dutton and Fitzpatrick 1975). Unfortunate- when lizards must spend long periods at low tem- ly, this is not a close simulation of the thermal perature without being able to feed. conditions which reptiles encounter under natural conditions. Although small reptiles are ectother- mic, during the day they utilise solar radiation and various behavioural devices to maintain body tem- perature well above ambient, while during the Introduction night body temperature drops to or near ambient Most of the early work on thermal acclimation (Stebbins and Barwick 1968; Avery 1971). Thus in ectotherms consisted of acclimating groups of under natural conditions many reptiles experience animals to different but constant temperatures and considerable fluctuation in body temperature over then measuring metabolic rates of the different a 24 h period. Therefore, although results from groups at various temperatures (Precht 1958; metabolic rate studies on reptiles acclimated to Prosser 1958, 1973). This approach was justified constant temperatures demonstrate the acclima- tory responses of animals to these specific condi- Abbreviations: G ~2 gravid females; NG ~ nongravid females tions, their usefulness in predicting the responses * Present address : Department of Biology, Chancellor College, of reptiles to seasonal temperature changes in the University of Malawi, P.O. Box 280, Zomba, Malawi field must be questioned. 312 J.W. Patterson and P.M.C. Davies: Metabolic rate of Psammodromus hispanicus

We report here on the acclimatory responses Temperature relations during the light period. In order to set of Psamrnodromus hispanicus, a small Spanish liz- an upper limit to the temperature at which metabolic rate was to be measured, body temperatures of Psammodromus hispani- ard. In this study, the lizards were acclimated to eus allowed access to a source of heat were measured in a four different night time temperatures but were 41 x 26 x 26 cm high glass aquarium kept in a room maintained able to raise their body temperatures by basking at the night time temperature of the season under study. Cover, during the day. In addition, data are presented food and water were constantly available, and a 100 W light on the effect of sexual condition on metabolic rate. bulb attached to the underside of the lid served as a source of both light and heat. For testing, lizards were placed in the aquarium in the evening. The light bulb was switched on at 10.00 h the following day and left on until 18.00 h. The body Materials and methods temperature of each lizard was measured five or six times at regular intervals, from one hour after the light bulb was turned Origin and laboratory maintenance of animals. Adult Psammod- on, by inserting the bulb of a Schultheis fast-registering mercury romus hispanicus were collected in the vicinity of Calpe on the thermometer into the lizard's cloaca. The mean body tempera- Mediterranean coast of Spain (latitude 38~ longitude ture of individual lizards was computed as the mean of these 0~ between 1st and 11 th April 1975. readings. In the laboratory, the lizards were housed in glass aquaria These tests were run with three or four lizards in the aquar- 92 x 31 x 31 cm high in a constant temperature room with facili- ium at the same time. At no time did there appear to be compe- ties for the automatic control of photoperiod. Each aquarium tition for basking sites, nor were any aggressive interactions was covered with a wooden lid. A 100 W light bulb which observed between the lizards. Therefore it is considered that was attached to the underside of the lid was turned on for the mean T b of individual lizards was unaffected by the presence the whole of the light period so that the lizards were able to of other lizards (see also Patterson and Davies 1978b). raise their body temperatures by behavioural thermoregulation during this period. During the dark period, the lizards' body Measurement of metabolic rate. In order to study the effect temperatures fell to the temperature of the constant tempera- of sexual condition on metabolic rate, lizards were classified ture room. Food (small larvae of Tenebrio molitor and second as either males (3), nongravid females (NG~) or gravid gemales instar larvae of Locusta migratoria) and water were constantly (G(?). G(~ were those in which the posterior part of the abdomen available, and were supplemented once a week with calcium was much distended and which were therefore in the terminal and multivitamin preparations. phases of egg maturation; G~ were present only in spring and summer because only at these seasons are eggs produced. NG? Seasonal acclimation. Climatic data for the different seasons were those females in which the posterior part of the abdomen were obtained from Meteorological Office (1964) and List was not distended; in spring they were in the early stages of (1968). For the purposes of this study, spring is defined as egg maturation whereas at other seasons they were not matur- March to May, summer as June to August, autumn as Sep- ing eggs. tember to November and winter as December to February. Metabolic rate was measured as the rate of oxygen con- The mean night time temperature for each season was assumed sumption. All measurements of oxygen consumption were per- to be the mean of the daily minimum temperatures for each formed in constant pressure respirometers, having both of the months which make up that season. For each seasonal and compensation chambers, immersed in a constant tempera- acclimation regime, the temperature of the constant tempera- ture water bath in which temperature was regulated by both ture room was set at the mean night time temperature for that a heating and a cooling unit. season and lights were turned on in the room every day for Prior to being used for respirometry, Psammodromus a period corresponding to the mean photoperiod of that season. hispanicus were fasted for three to seven days. After this fast, Photoperiodic and night time temperature data for the four experimental lizards were held overnight at the temperature seasons are shown in Table 1. Psammodromus hispanicus were of the constant temperature room and then, in the morning, allowed to acclimate to these seasonal regimes for at least four placed in the animal chambers of the respirometers which were weeks before any measurements were made. Since it is likely then fully assembled and placed in the water bath. Small bags that lizards show circannual rhythmicity (Lieht 1972; Cuellar of soda lime were present in both animal and compensation and Cuellar 1977a, b) and since this might affect metabolic chambers to absorb carbon dioxide. After the apparatus was rate, it was considered desirable to study lizards under different set up, a period of at least one hour was allowed to elapse seasonal acclimation regimes at the time of year when those before any measurements were made; this is adequate time for seasons actually occur. Therefore spring acclimated lizards were equilibration and for animals to recover from the effects of studied from March to May, summer acclimated lizards from handling. After this period, the taps were closed and five or June to August, and so on. six measurements of oxygen consumption were made. A close watch was kept on animals in the respirometers both during the period of equilibration and after the taps were closed, and Table 1. Photoperiod and night time temperature acclimation the results were used only if the animals did not move. Similarly, regimes for the four seasons where successive readings from the same animal were erratic, the results were discarded. Since it was necessary to watch the Season Photoperiod Night time animals during the course of the experiments, respirometry was Light : Dark temperature conducted with animals at a low level of illumination rather (h) (~ than in darkness. At the end of the experiment, the taps were opened, the respirometers taken out of the water bath and the Spring 13:11 10 lizards removed and weighed. Oxygen consumption rates were Summer 14:10 20 calculated in ILl g- 1 h-1 and converted to standard conditions Autumn 11:13 15 by the method of Scholander et al. (1952). Oxygen consumption Win~r 10:14 5 rates were measured in this way on five lizards of each sexual J.W. Patterson and P.M.C. Davies: Metabolic rate of Psammodromus hispanieus 3t 3

condition and at each season and temperature. The rates in cant difference in mean T b between summer and all cases can be assumed to approximate resting metabolic rate. autumn or between spring and winter but both spring and winter were significantly lower than ei- Statistical analysis'. Statistical analysis of the results was con- ducted using methods in Steele and Torrie (1960) and Sokal ther summer or autumn mean T b. In view of this, and Rohlf (1969). Differences between treatment means were it was decided to measure rates of oxygen con- considered significant when P< 0.05. sumption in all four seasonal acclimation groups in 5 ~ steps from 5 ~ to 30 ~ 5 ~ approxi- Results mates the lowest temperature to which this species is exposed at any season while 30 ~ approximates Temperature relations during the light period the maximum to which the lizards raise their body temperatures during winter and spring. In addi- Mean T b maintained by Psammodromus hispanicus tion, rates of oxygen consumption were measured during the four seasons are shown in Table 2. at 35 ~ in the summer and autumn groups since Analysis of variance (ANOVA) demonstrated a these animals maintained slightly higher body tem- significant effect of season on mean T b (P< 0.001). peratures. Further analysis with Duncan's 5% New Multiple Range Test demonstrated that there was no signifi- Metabolic rate Rates of oxygen consumption for lizards of differ- Table 2. Mean T b maintained by Psammodromus hispanicus al- ent sexual condition determined under conditions lowed access to heat lamps at different seasons of different seasonal acclimation and at different Season N Mean T b (~ measuring temperatures are shown in Table 3. It 97-+ SD is evident that, as with other ectotherms, in general metabolic rate increases with temperature although Spring 12 30.6 -+ 1.0 in most cases the magnitude of these increases (ex- Summer 5 32.6-+ 1.2 pressed by Qlo) is greater at low temperatures than Autumn 6 32.3 + 0.7 Winter 6 29.0-+ 1.5 at high temperatures. Therefore it is likely that also the resting metabolic rate of Psammodromus

Table 3. Rates of oxygen consumption for Psammodromus hispanicus. 2-+ SD

Season Sexual Weight Oxygen consumption rate (pl O 2 g-1 h-1) at temperature (~ condition (g) 5 10 15 20 25 30 35

Spring ~) 1.734 21.40 31.56 84.48 127.8 250.3 398.5 -+0.197 -+2.84 +11.29 _+16.06 +30.6 -+47.2 _+62.8 NG~2 1,265 25.21 31.43 97.65 117.0 168.3 363.2 +0,174 _+3.99 _+7.47 _+43.08 -+13.5 _+ 27.9 _+133.1 G~ 1.426 22.10 36.99 102.7 174.9 231.6 328.8 +0.152 _+4.77 _+8.48 _+52.1 4-54,8 _+85.9 _+ 50.7 Summer ~ 1.804 37.11 48.05 66.75 114.4 211.9 366.9 465.8 -+0.233 +3.09 +7.22 _+11.09 _+34.1 +38.4 -+69.1 • 127.3 NG9 1.161 26.64 40.58 72.25 151.9 262.5 404.2 442.9 _+0.146 _+4.11 _+4.62 +10.86 _+19.2 -+88.0 -+111.9 _+ 70.0 G~ 1.591 31,52 40.44 60,30 118.3 240,8 424.6 382.1 -+0.345 -+5.24 _+11.09 _+18.42 _+22.3 ___73.9 _+85.1 _+57.8 Autumn ~ 1.861 27.89 43.85 68.50 124.5 235.2 346.2 390.1 _+0.174 +4.49 -+10.14 -+7.90 _+27.0 -+41.9 _+60.1 __+72.1 NG~ 1.318 26.67 45.31 51.27 135.3 250.6 287.3 418.2 _+0,180 _+6.61 +5.74 _+6.11 _+27.8 -+30.1 _+ 52.2 _+ 24.4 Winter c~ 1.906 15.55 34.62 74.17 122.8 234,8 338.4 _+0,203 _+2.02 _+3.03 _+13.20 _+29.1 _+36.2 • 47.4 NG~ 1.400 14.52 32.99 59.30 129.9 212.4 314.5 _+0.195 _+1.33 -+2.65 _+9.06 +21.8 _+10.0 +39.7 324 J.W. Patterson and P.M.C. Davies: Metabolic rate of Psammodromus hispanicus

Table 4. ANOVA P-values for rates of oxygen consumption of Psammodromus hispanicus (N.S. = non-significant, i.e. P > 0.05)

Source of variation Temperature (~

5 10 15 20 25 30 35

Between seasons < 0.001 <0.001 0.005-0.001 N.S. N.S. N.S. N.S. Between sexual conditions N.S. N.S. N.S. N.S. N.S. N.S. N.S. Interaction 0.025-0.01 N.S. N.S. 0.025-0.01 0.025-0.01 N.S. N.S.

Table 5. Summary of Duncan's 5% New Multiple Range Test on rates of oxygen consumption of Psammodromus hispanicus a

Temper- Season and sexual condition ature (~ Spring Summer Autumn Winter

NG9 Gq? d' NG~ G~ c~ NG• ~ NG~

5 21.40 25.21 22.10 37.21 26.64 32.52 27.89 26.67 15.55 14.52

10 31.56 31.43 36.99 48.05 40.58 40.44 43.85 45.31 34.62 32.99

15 84.48 97.65 102.7 66.75 72.25 60.30 68.50 51.27 74.t7 59.30

20 127.8 117.0 174.9 214.4 151.9 128.3 124.5 135.3 1~2.8 229.9

25 250.3 168.3 231.6 212.9 262.5 240.8 235.2 250.6 234.8 212.4 a Each figure in the body of the Table is the mean rate of oxygen consumption for that group. Those means not underscored by a common line or a line at the same level are significantly different from each other (i.e. P<0.05). hispanicus is more temperature sensitive at the rates than summer and autumn animals at 5 ~ lower than at the higher temperature ranges. At 10 ~ winter and spring animals have a lower To test for effects of season and sexual condi- metabolic rate than summer and autumn animals tion on metabolic rate, these data were analysed while at 15 ~ animals in spring have significantly by means of ANOVA. Two way ANOVA was per- higher metabolic rates than at other seasons. At formed on data for each temperature and the P- 20 ~ gravid females in spring respire at higher values are shown in Table 4. At no temperature rates than any others except NG~? in summer, and did sexual condition alone have any significant ef- at 25 ~ NG~ in spring have a lower metabolic fect on metabolic rate. However, season showed rate than any others apart from c~ in summer and significant effects at 5 ~ 10 ~ and 15 ~ and NG? in winter. It is evident from the above that, interaction (season x sexual condition) showed sig- apart from temperature, the major effect on meta- nificant effects at 5 ~ 20 ~ and 25 ~ No signifi- bolic rate is season, and that seasonal effects occur cant effects were demonstrated at 30 ~ or 35 ~ mainly at low temperatures. For those temperatures at which ANOVA demon- strated significant effects, the data were analysed Discussion further with Duncan's 5% New Multiple Range Test to test for significant differences between There is considerable variation in the temperature treatment means. The results are summarised in sensitivity of metabolic rate. In some spe- Table 5. At 5 ~ the metabolic rate in winter is cies, Qlo is constant over a wide range of tempera- significantly lower than that of animals at any tures (Prieto and Whitford 1971; Snyder 1975), other season, while the metabolic rate of males whereas in others the Q10 varies, usually having in summer is significantly higher than all others; lower values at the higher temperatures (Snyder in general, spring animals have lower metabolic and Weathers 1976; Fitzpatrick et al. 1978). Psam- J.W. Patterson and P.M.C. Davies: Metabolic rate of Psammodromus hispanicus 315 modromus hispanicus belongs to the latter group. dest seasons (spring and winter) are also the sea- Such a pattern of temperature sensitivity presum- sons when there are the longest periods of heavy ably allows the animal to have relative metabolic cloud cover (see Meteorological Office 1964) dur- independence from temperature changes around ing which the lizards are unable to raise body tem- the preferred temperature (hence the low Qlo) perature by basking and thus must spend long peri- while allowing energy to be conserved during inact- ods at low temperature without being able to feed. ivity at low temperatures (Bennett and Dawson This study demonstrates that in Psammodro- 1976). mus hispanicus acclimated to seasonal conditions Sexual condition had little effect on resting of night time temperature and photoperiod, differ- metabolic rate of Psammodromus hispanicus. It is ences in metabolic rate between acclimation groups known that in some species of amphibians (Dunlap occur only at low temperatures. These tempera- 1969; Fitzpatrick 1971) and reptiles (Dutton and tures are experienced during the dark period by Fitzpatrick 1975), including other species of Euro- some acclimation groups but not by others. Thus pean lacertid lizards (Patterson and Davies, in it appears that the biologically important thermal preparation), the metabolic rate of G~2 is higher difference between the seasons is the level to which than that of NG~ and d~, but no such effects are the temperature drops at night. During the day, evident for Psammodromus hispanicus. providing that the sun shines, the lizards are able Apart from temperature, the major influence to raise body temperature by basking to a level on metabolic rate is seasonal acclimation, and an which is relatively independent of season. examination of Tables 4 and 5 demonstrates that seasonal effects are most evident at low tempera- Acknowledgements'. This study was supported by a grant from tures (5 ~ and 10 ~ In general, resting metabol- the Science Research Council, UK. We thank an anonymous reviewer for comments on an earlier draft of the manuscript. ic rate at 5 ~ and 10 ~ is lower in spring and winter than in summer and autumn acclimated ani- mals. The spring and winter groups were accli- mated to lower night time temperatures than the References summer and autumn groups, so it is possible that Avery RA (1971) Estimates of food consumption by the lizard acclimation to low night time temperature reduces Lacerta vivipara Jacquin. J Anim Ecol 40:351 366 low temperature metabolic rate. However, photo- Bennett AF, Dawson WR (1976) Metabolism In: Gans C0 Daw- period as well as night time temperature was varied son WR (eds) Biology of the reptilia, vol 5, Physiology A. Academic Press, London, pp 127-223 between the seasonal acclimation groups so it is Cuellar HS, Cuellar O (1977a) Refractoriness in female lizard possible that the difference in metabolic rate be- reproduction: a probable circannual clock. Science tween the seasons may have been induced, at least 197 : 495-497 in part, by photoperiodic differences. Photoperiod Cuellar HS, Cuellar O (1977b) Evidence for endogenous rhyth- micity in the reproductive cycle of the parthenogenetic lizard affects the metabolic rate of some animals (Whit- Cnemidophorus uniparens (Reptilia: Teiidae). Copeia ford and Hutchison 1965) but not others (Wood 1977:554-557 and Orr 1969; Fitzpatrick 1971). However, if the Dunlap DG (1969) Influence of temperature and duration of seasonal effects on low temperature metabolism acclimation, time of day, sex, and body weight on metabolic are due to differences in night time temperature, rates in the hylid frog, Acris crepitans. Comp Biochem Phys- iol 31 : 555-570 acclimation to low night time temperature reduces Dunlap DG (1971) Acutely measured rate-temperature curves low temperature metabolism in Psammodromus in the cricket frog, Acris crepitans. Comp Biochem Physiol hispanicus and therefore this species at low temper- 38A:1-16 ature appears to exhibit Precht type 5 or inverse Dutton RH, Fitzpatrick LC (1975) Metabolic compensation to seasonal temperatures in the rusty lizard, Sceloporus oli- acclimation (Precht 1958; Prosser 1958, 1973). In- vaceus. Comp Biochem Physiol 51A: 309-318 verse thermal acclimation has been recorded in a Fitzpatrick LC (1971) Influence of sex and reproductive condi- number of other animals, including some reptiles tion on metabolic rates in the Allegheny Mountain salaman- (Jacobson and Whitford 1970; Patterson and Da- der Desmognathus ochrophaeus. Comp Biochem Physiol vies 1978a, b) and has usually been interpreted 40A: 603-608 Fitzpatrick LC, Bristol JR, Stokes RM (1972) Thermal acclima- as a method of energy conservation at tempera- tion and metabolic rates in the dusky salamander Desmo- tures too low for the animal to be able to gather gnathusfuscus. Comp Biochem Physiol 41A:89-96 food effectively (Dunlap 1971; Fitzpatrick et al. Fitzpatrick LC, Hughes JL, Venables BJ (1978) Relations be- 1972; Hazel and Prosser 1974; Patterson and Da- tween preferred body temperatures and metabolic compen- sation in the rusty lizard Sceloporus olivaceus. Comp Bio- vies 1978 b). A similar explanation will account for chem Physiol 59A: 13-16 the results of this present study since in the area Fry FEJ, Hochachka PW (/970) Fish. In: Whittow GC (ed) where Psammodromus hispanicus occurs, the col- Comparative physiology of thermoregulation, vol II. Inver- 316 J.W. Patterson and P.M.C. Davies: Metabolic rate of Psammodromus hispanicus

tebrates and nonmammalian vertebrates. Academic Press, temperature in the horned lizard, Phrynosoma cornutum and New York, pp 79-134 Phrynosoma douglassii. Copeia 1971:498-504 Gelineo S (1965) Metabolic adaptations of lizards to thermal Prosser CL (1958) General summary: the nature of physiologi- environment. Glas Srp Akad Nauka Urnet Od Priv Mat cal adaptation. In: Prosser CL (ed) Physiological adapta- Nauka 262:17-35 tion. American Physiological Society, Washington, DC, Hazel JR, Prosser CL (1974) Molecular mechanisms of temper- pp 167-180 ature compensation in poikilotherms. Physiol Rev Prosser CL (ed) (1973) Comparative animal physiology, 3rd 54:620-677 edn. Saunders Co, Philadelphia Jacobson ER, Whitford WG (1970) The effect of acclimation Scholander PF, Claff CL, Andrews JR, Wallach DF (1952) on physiological responses to temperature in the snakes, Microvolumetric respirometry. J Gen Physiol 35 : 375-395 Thamnophis proximus and Natrix rhombifera. Comp Bio- Snyder GK (1975) Respiratory and evaporative water loss in chem Physiol 35:439-449 a small tropical lizard. J Comp Physiol 104:13-18 Licht P (1972) Physiology of breeding cycles in reptiles. Gen Snyder GK, Weathers WW (1976) Physiological responses to Comp Endocrinol Suppl 3:477-482 temperature in the tropical lizard, Hemidaetylus frenatus List RJ (1968) Smithsonian meteorological tables, 6th revised (Sauria: Gekkonidae). Herpetologica 32:252-256 edition. Smithsonian Institution, Washington Sokal RR, Rohlf FJ (1969) Biometry: the principles and prac- Meteorological Office (1964) Weather in the Mediterranean, tice of statistics in biological research. W.H. Freeman and vol II, 2nd edn. H.M.S.O., London Co, San Francisco Murrish DE, Vance VJ (1968) Physiological responses to tem- Stebbins RC, Barwick RE (1968) Radiotelemetric study of ther- perature acclimation in the lizard, Uta mearsni. Comp Bio- moregulation in a lace monitor. Copeia 1968:541-547 chem Physiol 27 : 329-337 Steele RGD, Torrie JH (1960) Principles and procedures in Patterson JW, Davies PMC (1978a) Thermal acclimation in statistics. McGraw-Hill, New York temperate lizards. Nature 275:646-647 Vernberg F J, Vernberg WB (1970) Aquatic invertebrates. In: Patterson JW, Davies PMC (1978b) Energy expenditure and Whittow GC (ed) Comparative physiology of thermoregula- metabolic adaptation during winter dormancy in the lizard tion, vol I. Invertebrates and nonmammalian vertebrates. Lacerta vivipara Jacquin. J Thermal Biol 3:183-186 Academic Press, New York, pp 1-14 Precht H (1958) Concepts of the temperature adaptations of Whitford WG, Hutchison VH (1965) Gas exchange in salaman- unchanging reaction systems of cold-blooded animals. In: ders. Physiol Zool 38:228-242 Prosser CL (ed) Physiological adaptation. American Physio- Wood SC, Orr LP (1969) Effect of photoperiod and size on logical Society, Washington, DC, pp 50-78 the oxygen consumption of the dusky salamander Desmo- Prieto AA Jr, Whitford WG (1971) Physiological responses to gnathus ochrophaeus. Ohio J Sci 69:121 125