Vol. 8, pp. 1-6

Asiatic Herpetological Research

1999

The Activity and Thermal Biology of the Fossorial Reptile, Diplometopon
zarudnyi (Amphisbaenia: Trogonophiidae) in Central Saudi Arabia

AWADH M. AL-JOHANY
Department of Zoology, College of Science, King Saud University, P.O.Box 2455, Riyadh II 45 1, Saudi Arabia.
Abstract .- The nocturnal activity of the fossorial amphisbaenid Diplometopon zarudnyi was studied in the field

and its thermal selection and tolerance were determined in the laboratory. During the study period (summer) the
animals commenced activity at 20.00 hrs (ground temperature 30-32°C) and finish their foraging between 3.00 to
4.00 hrs (ground temperature 28-26°C) before the break of dawn. The mean activity temperature determined in
the field was 31.5°C, which was usually 0.5 to 1°C higher than the ground temperature. The mean selected bodytemperatures in a gradient during day and night were 26.4°C (range 15-38°C) and 26.3°C (range 14-38°C)
respectively. The Critical Thermal Maximum was 47.6°C and the Critical Thermal Minimum was 7°C. D.

zarudnyi tolerates a wide range of temperatures while maintaining its mean body temperature within a narrow
range. The role of Selected Body Temperature is discussed in relation to metabolism.

Key words.- Amphisbaenia, Trogonophiidae, fossorial reptile, Diplometopon zarudnyi, Saudi Arabia, Central
Arabia, activity, thermal preference, thermal tolerance.

Introduction
The amphishaenian family Trogonophiidae is represented in central Arabia by the single species Diplom-

etopon zarudnyi ( Al-Sadoon, 1988). The range of thisspecies extends to northern Arabia and the coastal

Arabian Gulf (Arnold, 1986). D. zarudnyi is an oscillating digger, commonly found burrowing in low sanddunes in open terrain and in sub-surface soils of datepalm farms. This amphisbaenian is a nocturnal forager, sometimes occupying ant and termite tunnels.
In this study the nocturnal activity of D.

zarudnyi

was studied in the field, and its thermal selection and

Figure 2. Setup used to measure the selected bodytemperature tolerance were determined in the laboratory. A comparison of results of this study has been

temperature: (1) Telethermometer, (2) Thermal gradient, (3) Thermostat heater, (4) Cooling coil in water

made with the results of other species from different

bath, (5) Refrigerant machine, (6) 10 cm thick sandgeographical habitats.

layer, (7)tored every hour from dusk to dawn.

Several field trips were made during the summer sea-son (July- August.) to habitats of D. zarudnyi

locatedaround Riyadh city (Thummama and Dilam). Noctur-

activity

period.

was observed during the

Rechargeable

W heating bulb, (8) Thermistor probe.

U.S. A). Air and ground temperature were also moni-Material and Methods

nal activity of the animals

100

fluorescentlanterns

Thirty D. zarudnyi (adult animals of both sexes)

were used in the laboratory study (mean mass = 7.63

SD ± 2.54; mean SVL=182 mm, SD ± 13.4; mean
VTL=14 mm, SD ± 2.0). They were collected fromg,variouslocationsaround Riyadh

city.

They were

were employed to illuminate the area being studied.

maintained for short periods in Plexiglass boxes filled

When tracks appeared on the sand surface, they werewith 10 cm of clean sand. The sand was sprinkled
periodically with water. Mealworms and water were

followed up to the location of the animal, which waseither dug out of its subsurface position byusing a small

hand orhand shovel. Soil temperature (T s ), airtemperature (Ta ) and cloacal body temperature (T b )were taken within 15 seconds of capture by a quick
reading cloacal thermometer (Millar and Weber Co.,available ad lib. The laboratory temperature was 23 ±1.5°C.

The Selected Body Temperature (SBT) of ten
amphisbaenians was determined in a metal thermal

1999

Asiatic Herpetological ResearchVol. 8, p.

minute). The probe remained inserted in the cloaca
and the body temperature was monitored continuously while the test chamber sand was gradually

heated or cooled.

Figure 2. Method employed to tie the thermistor; theprobe (1) inserted inside the animal's cloaca andlooped to be held on the tail (2) with bands of adhesive

To determine the CTMax and CTMin, the amphisbaenian was observed until the animal lost its righting
response when it was turned on its back. During the

CTMin experiments, after initial cooling (9.5°C), thetape.

animal lost its ability to right itself but, after its belly

gradient which measured 200 x 25 x 40 cm (Fig.l).
Sand was spread evenly to a depth of 10 cm on thewas touched by a fine paint brush, the animal exhibited a wave of convulsions down the body. Further

base of the gradient. A temperature gradient from 10-

50°C was achieved by fitting a thermostatic hot plate
below one end and by placing an insulated ice container constantly frozen by an immersion refrigerant
coil on the other end. The surface sand at the cool end

wassprinkled with water intermittently to prevent
desiccation. The gradient was illuminated by two 100

watt bulbs suspended 80 cm from the surface of thesand controlled by an electronic timer to maintain thephotoperiod. The animals were left in the gradient for
one day prior to the start of the experiment for accli-

cooling led to total loss of all responses, and the temperature at which this occurred was designated as theCTMin.

All but

one experimental animal survived

after returning to room temperature. After 10 days, theanimals which were used for

CTMax experiments

were used to measure CTMin. The CTMin of theseanimals was compared to that of the first group.
Statisticalanalysis

was performed using

GLM

procedure of Minitab package (version 8.2). Two-way
analysis of variance (ANOVA) with interaction(unbalanced) was used for data analysis (P=<0.05).

mation.

The cloacal body temperature (Tb was monitored)

probes (Model 511; Yellow
Theprobes were connected to a multiSprings Inc.).
channel YSI Telethermometer, and an Omniscribe
Houston Instruments continuous chart recorder. The
with highsensitivity

Results
The nocturnal activity of the animals is clearly defined
during summer nights. Emergence for foraging activthe air temperature is 30ity begins at 22.00 hrs when

cm into the cloaca and held in place with 3-4 mm

32 °C and the ground temperature is 32-34°C. The
foraging activity subsides between 03.00 to 04.00 hrs
when the air temperature is 28-26°C and the groundbands of adhesive tape (Fig. 2). The probes remainedin place even when the animal burrowed below thetemperature is 27-25°C. After this the animals movedeeper into the sand surface (presumably to their bur-sand. Twenty four hour continuous recording of T brows or refuges) and no kind of activity is observed

was obtained for three days on each animal and one
measurement for each hour was recorded.

during the daylight hours.

flexible tip of the pre-calibrated probe was inserted for
1

The animals

wereactivebetweenadjacently

These instruments were also used to measure thelocated shrubby small sand dunes. Most of these sand

Critical Thermal Maximum (CTMax) and the Criticaldunes hosted colonies of ant and termite mounds.
Movement is typically a combination of sub-surface

Thermal Minimum (CTMin).

CTMax is thearith-

metic mean of the collective thermal points at which

locomotor activity becomes disorganized and the ani-

mal loses its ability to escape from conditions thatwill promptly lead to its death. CTMin is the low temperature that produces cold narcosis and prevents
sheet metal
locomotion (Pough and Gans, 1982).

A

box (25 X 20 cm) filled with a layer of sand and kept
above a thermostat heater was employed to measure
CTMax. For CTMin, a Plexiglass box (25 X 15 cm)
with a layer of sand held inside a larger insulated box
surrounded by ice cubes was employed. Twenty different animals ( 10 for each category) were used. Eachanimal was gradually heated or cooled inside theexperimental chambers 1 °C increase or decrease per(and surface locomotion. Undisturbed movement of
the animal over the surface of the sand was observed
only two instances. On the rest of the occasions theanimals were tracked by their impressions in the sand.
The animals move just below the surface of the sandfor two or three meters by piercing and wiggling bystrong head and body movement (probably in searchof termites). After that they come out on the surface

and effortlessly glide on the sand surface for several
subsequent spring action. This wasVdone by making an S' shape of the body and flicking
meters by

fast

forward. Consequently this kind of activity leaves a
distinct pattern of tracks on the sand surface which

Asiatic Herpetological Research

1999

Vol. 8. p. 3

35 0-ir= 0.6648

32.5

P=0.0132
n=13

E

i

s
I

30.0

M
%C

E
a

m

27.5

——

250

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

i

27

28

29

30

31

32

33

34

Figure 4. Representation of body temperature selec-

35.0

r=06588

O 32.5tion (%) by Diplometopon zarudnyi in the thermal gra-

P=0.0143n=13

dient during day and night periods.

gradual decrease of body temperature tovalue by the end of the light period.

300-

Temperature "CitslowestDuring the CTMax trials, animals below the soil
27.5-

surface emerged when the sand temperature reached

B
25.04
27

40°C. The CTMax
trials,

28

29

33

31

34

Body Temperature 'C
Figure 3. A. Relationship between body temperature(Tb) and soil temperature (Ts). B. Relationshipbetween body temperature (Tb) and air temperature(Ta). (The regression line, significance value and sample size are as indicated).

can be easily differentiated between the tracks ofother animals of the habitat.

The mean field body temperature for the active
animals captured was 31.5°C (range 29.5 - 32.5°C;
n=13). Regression analysis showed a significant difference between the T\, - Ta and T^, - T s (P<0.05; Fig.

The mean selected temperatures in the gradientduring the day and night were 26.4°C (SD ± 5.2) and26.3 °C (SD ± 5.7) respectively; the temperatures
selected during day ranged between 15 and 38°C andbetween 14 and 38°C during the night (Fig.4). About3).

was 47.6°C. During the CTMin

the animals lost the righting reflex

at

9.4°C

(SD±1) and CTMin was 7°C (SD±0.6). The second
group of animals used in measuring CTMin lost therighting reflex at 11.3°C (SD±1.1) and CTMin wasreached at 9.5°C (SD±0.5).

Discussion
D. zarudnyi come out of their refuges at night when
the air temperature and the soil surface temperature
are favorable. By employing two kinds of locomotion
the task of foraging

isaccomplished. They expend

vigorous efforts on their foraging activity, since they

have to accomplish it in a short duration: multiple
tracks crossing each other were observed for a single
in a wide area, giving a false impression ofanimals
manybeing active. This lead to many deadanimalends while following the leads of the tracks.
Previous reports (gradient studies) assumed thatthe body temperatures of amphisbaenians are equal toninety percent of D. zarudnyi selected temperaturessoil

between 23 and 36°C during the day and between 21

the soil surrounding the animals. For a more accurate

and 36 C during the night. Temperature selected did
notdiffersignificantly

between

day

and

night

(F=0. 14, P=0.705). However, individuals differed sigselected(F=l 27.37,
temperatures
P=0.001 ). Also, there was a highly significant interacnificantly

intion between individuals and the time of day (F=7.72,

P=0.001 ). The average hourly temperature pattern of
D. zarudnyi showed a gradual increase of body temperature (in the gradient) and reached its highest level
just before the end of the dark period (Fig. 5), and atemperatures, since readings were obtained from

evaluation,

here,

we

recordedbodytemperatures

direct and continuously in the thermal gradient.

The selected mean temperature in the gradient(26°C) measured in this study explains the Metabolic
rate-Temperature curve (M-T curve) reported for D.
zarudnyi; in which both the adults (mean wt.6.34 g)
and sub-adults (mean wt.3.15 g) showed stable Ot

consumption1986).

rates

between25-30°C(Al-Sadoon,

1999

Asiatic Herpetological ResearchVol. 8, p. 4

28.0

n=10

27.5

O

27.0

a

I

26.5

Q.

E

26.0

«
255
25.0

24 5
_i

24.0

— ——
i

i

1_

6h

24 h

18 h

12h

18 h

Time
in the thermal gradient during
Figure 5. Mean selected body temperature pattern of Diplometopon zarudnyi
hours. Numbers at each point indicate the SEM.

The body temperature for active D. zarudnyi arethan in the laboratory because thehigher in the field

24

13.4 -27.8°C which is low and as well clearly indicates thermoregulation.

animals were deprived of food during the experiment,

The low temperature selection of D. zarudnyi

and also may be the result of confinement to a limited

also in line with the observations made on other bur-spacein the gradient.

strated that the

Van Berkum (1980) demon-

SBT is lower in lizards with decreasedfood consumption. It is recommended to measure
metabolism during the post absorptive state of digestion, so as to minimize any contribution of specificdynamic action (Eckert and Randall, 1983).
temperature (26°C) could extend activity and stabilize

present

resultsinthesub-surface

supplement

thespecies

habitat.

The

previous publishedreports of lower temperature selection in amphisbaenians. Avery (1982) noted that many fossorial snakes,

amphisbaenians, sea snakes, fresh water and marine

selected body temperatures were also reported for

Anguis fragilis (Gregory, 1980).

A previous study showed that D. zarudnyi had noendogenous circadian rhythm and no periodicity inalternating light and darkness although it was more
activeat1979).

The

was reported by Abe(1984); mean field body temperature and preferredtemperature in the gradient was 21.1°C and 21.4°C
al.

(1990)

reported

marked field thermoregulation in Blanus cinereus andbody temperatures. Gatten and1981) reported the low mean body temperMcClung (itselected low fieldature for Trogonophis weigmanni in a range of 21.7°C
to 23.4°C.

A field study of Bipes biporus demon-

strated that thisworm lizard can thermoregulate if

necessary, by vertical and horizontal changes in substrate positioning (Papenfuss,

et al.,

1982).

Bolgooyen

Uropeltidae also appear to select a low body temperabetween 18°C and 20°C (Gans,1973). Low

appear not to thermoregulate and that many

et.

and

tures

low temperatures. Evidence of thermoregula-MartinBuryof small snakes to select lower temperatures than sur-selectrespectively. Also,

reptiles.

25°C. Clark ( 1968) reported five subterranean species

turtles,tion in Amphisbaena mertensiof(1976) determined the thermal preferendum of the
24legless burrowing lizard Anniella pulchra to be

face dwelling species. Burrowing snakes of the family

As D. zarudnyi is fossorial, the low mean selectedbody metabolism

rowingisMore recently,(1995) during a field study ofDiaz-Paniagua
seasonal and diel activity of Blanus cinereus, reported

an activity range of ground temperatures between

high temperatures (Cloudsley-Thompson,
finding in the present study wherein

Diplometopon showed no significant difference
between day and night time temperature selection isconsistent with the lack of an endogenous circadianrhythm in temperatures selected in day and night.
However, in the present results there is a highly significant difference among individuals. This is probain body weight,
bly due to individual differences
health status, age and sex of the animals tested.

In the gradient D. zarudnyi elevated its body tem-of the night, a time
perature slightly in the second halfwhen they were seen to forage actively in the field. In
T. wiegmanni tested in a thermal gradientelevatedshowedtemperatures in the afternoon andearly evening (Gatten and McClung, 1981). Foraging

contrast,

activity at dawn and in early morning

also is reported

Asiatic Herpetological Research

1999

Vol. 8, p. 5

for Agamodon anguliceps from Somalia; the animals

Al-Sadoon. M. K. 1988. Survey of the reptilian fauna

were located in the top 2-3 inches of the soil at dawn,of theappearing to have

moved upwards

during the night.

Kingdom of Saudi Arabia II. The lizard andamphisbaenian fauna of Riyadh province. Bulletin

As temperatures rose, most animals disappeared fromofMaryland Herpetological Society 24: 58-76.

the top 6-12 inches of the ground (Gans and Pandit.

Arnold, E. N. 1986. A key and annonated check list to1965).

the lizards

The CTMax value for Diplometopon is similar tothat of certain terrestrial lizards of Central Arabia, but

and Amphisbaenians of Arabia. Fauna of

Saudi Arabia. 8: 385-432.

CTMin was higher than that reported for most

Avery, R. A. 1982. Field studies of body temperatureand thermoregulation. Pp 93-166. In: C.Gans andother sympatric lizards (Al-Johany, 1986). The relatively high CTMin might be related to the subterra-

F.H.Pough (eds), Biology of the Reptilia Vol 12, Academic Press, London.

thetemperatures encountered by Diplometopon
which seldom fall below freezing, unlike the surface

neanBury, R. B. and T.G. Bolgooyen. 1976. Temperature
selectivity in the legless lizard, Anniella pulchra.

°C. The 2.5 °C
temperatures which may drop below
increase in the CTMin for animals that had experi-

Copeia 1976: 152-155.

enced the CTMax might be attributed to a short-time

Clark, D. R. Jr. 1968. Experiments into selection ofheat-hardening effect (see Maness and Hutchison,soil type, soil1980).

Prior to this study there was no data available on
the held thermal ecology of D. zarudnyi. By the com-moisture level and temperature by fiveofsmall
snakes. Transactions of Kansas Acadspecies

emy of Sciences 70: 490-496.
Cloudsley -Thompson, J.L. 1979. Water loss and loco-

bined result of the field and laboratory study it is now

motory activity in Agarna persica and Diplometopon

confirmed that the animal is a thigmotherm but not in

zarudnyi from Kuwait. Journal of Arid Environments
2: 273-277.

its strict

sense. Since it was observed that the animal

C, M.C. Blazquez, C. Keller, A.C.
Andreu.G. Olmedo and J. A. Mateo. 1995. Observa-

manages (probably by metabolic activity) to keep its
body temperature a degree or half higher than the

Diaz-Paniagua,

ground temperature.

tions

on seasonal andamphisbaeniancinereus

Spain. Herpetological Journal Vol.5: 217-220.

AcknowledgmentsIsurface activity of thein south-western

dial

Blanusam thankful to Dr.Carl Gans, Department of Biol-ogy, University of Michigan, for helpfulcomments

andto Dr.Roger Avery, University of Bristol, formeticulous reading of the manuscript. Thanks are also

Eckert, R., and D. Randall. 1983. Animal Physiology,

Mechanisms and Adaptations, 2ndFreeman & Co., New York.

W.H.

Edition,due to Mr. Mohammed Yousuf for help in field work,

1973. Uropeltid snakes - survivors in aworld.
Endeavor. 32: 60-65.
changing

technical assistance in the laboratory and typing of theGans, C. and H.M. Pandit. 1965. Notes on a herpeto-manuscript.

logical

Literature Cited

amphisbaenian genus Agamodon Peters. Ann.
Zool., R.G. Mus. Afr. Cent. 134: 71-86.

Abe, A. S. 1984. Experimental and field record of pre-Gatten, R. E. Jr. and R.M. McClung. 1981. Thermal

ferred temperature in the neotropical amphisbaenid

selection by an amphisbaenian Trogonophis wiegmanni. Journal of Thermal Biology 6: 49-51.

Amphisbaena

mertensi

Stauch(Reptilia,

Amphis-baenidae). Comparative Biochemistry and Physiology

77A: 251-253.
Al-Johany, A. M. H. 1986. Ecology and reproductive
biology of Acanthodactylus schmiditi in Central Arabia.

Ph.D.Thesis. University of Southampton. U.K.

pp.

Al-Sadoon, M. K. 1986. Influence of a broad temperature range on the oxygen

consumption rates of threeGans, C.

collection

fromSomalirepublic

V.

The
in

8

Gregory, P. T. 1980. Physical factor selectivity in the
fossorial lizard Anguis fragilis. Journal of Herpetol-ogy 14: 95-99.
Maness, J.D. and V.H. Hutchison. 1980. Acute adjust-ment of thermal tolerance

in vertebrateectotherms

following exposure to critical thermal maxima. Journal of Thermal Biology 5: 225-233.
Martin. J., P. Lopez and A. Salvador. 1990. Field bodydesert lizard species. Comparative Biochemistry andtemperatures

Physiology 84A: 339-344.

cinereus. Amphibia-Reptilia

of

the

amphisbaenid
1

1:

87-96.

lizardBlanusVol. 8, p. 6

Asiatic Herpetological Research

Papenfuss, T.J. 1982. The ecology and systematics ofthe amphisbaenian genus Bipes. Occational
California Acadamy of Sciences 136: 1-42.

Paper,

Pough, F.H. and Gans, C. 1982. Biology of the Reptilia, Vol.12 Physiology C. Academic Press, London.
Templeton, J.R. 1970. Reptiles. Pp. 167-221. In:
Whittow, G.C (ed), Comparative physiology of thermoregulation. Vol. 1. Academic Press, New York.

van Berkum, F.H. 1980. The significance of preferredbody temperature of lizards. American Zoologist 20:734.

1999