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ACTIVITY METABOLISM IN THE LIZARD
SCELOPORUS OCCIDENTALIS
A L B E R T F. B E N N E T T A N D T O D D T . G L EE SO N
Schoo l of B iological Sciences, Un ivers ity of Ca liforn ia, Irv ine, Californ
Accepted 12/17/75)
Stan dard levels of oxygen consu mp tion an d oxygen consum ption an
duction during and after burst activity were measured in the iguanid
p us
occidentalis. T h e activ ity cap acity of this animal is restricted; it s
ous movem ent for only 1-2 min. Th e contribution of aerobic metabolis
tivity is strongly therm ally dep end ent. Maximal levels of oxygen con
achieved during activity at
3 0 4 0
C .
At lower temperatures, significant
oxygen up take , which app ear t o result from restricted ventilation. T
aerobic increase above resting levels occurs a t 5C, preferred body tem p
species. Repa ym ent of th e initial stages of oxygen d eb t is also mo st r
Lactic acid concentration reaches high levels during activity, and its
g r ea te st a t
30 C.
Anaerobic metabolism represents
62 -82y0
of th e e
during bu rst activ ity, accounting for nearly all of th e carb oh yd rate ca
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LBERT
F ENNETT ND
TODD T
GLEESON
accumulated lactate, and the capacity
for further activity is strongly curtailed
during the recovery period. These
generalizations also pertain to th e ac tivity
metabolism of many other reptilian
groups, b u t not to all Bartholomew an d
Tu cke r 1964; B en ne tt 1973b).
Certain methodological difficulties
hav e hampered th e examination of to ta l
energy metabolism, both anaerobic and
aerobic, during activity in the lower
vertebrates. Anaerobic energy produc-
tion can be estimated by the lactic acid
concentration in whole-body homoge-
nates, a procedure which avoids the
during and after stim
activity. These intervals
to permit a n accurate
con tributio n of aerobi
In addition, they can y
on th e therm al depende
eratio n of oxygen con
activity and of maxima
Sceloporus occidenta
fence lizard, is one of t
reptiles in southern C ali
in a gre at variety o
animals are territorial a
during the day on an
site of o ld lumber or
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CTIVITYMET BOLISM IN
LIZ RD
moths (Galleria sp.) and had access to
water a d libitum. Th e animals remained
healthy and active and were generally
held in captivity for less than 1 wk.
Animals were fasted for a t least 2 days
before experimentation.
In the experiments which determined
oxygen consumption and lac tate produc-
tion simultaneously during activity, a
single animal was weighed and measured.
Electrical leads were implanted
in
the
base of its tail. T h e lizard w as then
placed in a rectangular Lucite metabo-
lism cham ber (volume 534 cm3)
equipped with ports for air flow and
decrem ent was used to d
consumption according
Depocas and H a rt (195
The environmental
opened and incurrent a
po rts were closed, isola
the airtight chamber.
stimulated to maxim
electrical shocks of lo
livered with a Harvar
the implanted leads.
chamber was hit a nd s
the animal, which respo
of rapid running. Stim
tinued for 5 min. Air s
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68
ALBERT F BENNETT
AND
TODD
T
GLEESON
analyzer (see Depocas and Hart 1957).
Oxygen consumption during each minute
interval of activity and recovery was
calculated according to the formula
where
V volume of chamber (cm3) volume
of animal (cma)
V, volume of gas sample removed from
chamber (cm3)
RH
relative humidity in the cham-
figure 1. The thermal d
function is complex.
consumption is very s
ture dependent (Qlo
and 35 C but is essent
independent at 20-25 C
Such zones of therma
oxygen consumption
viously observed in o
Bennett and Dawson
nounced decrement i
consumption occurred
ning: the average eveni
below that in the af
decrease is not signific
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ACTIVITY METABOLISM
IN
A
LIZ RD
stimulation are reported in figure 2. The Qlo 30-35 C = 2.2, Q
total amount of oxygen consumed during
In addition to the gre
the period of stimulation increases with
consumption the rate
increasing temperature up to
35
C :
consumption increase
Qlo 20-25 C
=
2.9 Qlo 25-30 C
1.4
levels is also temperatu
ce lo ~o ru s occidental is
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70
LBERT F.
BENNETT
AND TODD T. GLEESON
20
C, maximal levels are not attained consumption are coinc
until after the cessation of activity and activity burst at
30-40
stimulation. As body temperature in- acceleration of oxygen c
creases, the rate a t which maximal rates ing the first minute of
of oxygen consumption are achieved also great between 20 and 2
increases until maximal levels of oxygen Ventilation during burs
TABLE
THE EROBIC I N C R E M E N T D U R I N G 2 M I N
OF
BURST ACTIVITY AND
SCOPE (MAXIMAL
MINUTE
AEROBI C
I N C R E M E N T )
IN
SCELOPO
OCCIDENTALIS
TIMULATED FOR MIN
AEROBIC
SCOPE
AEROBIC
I N C R E ~ N T
Time
TEW. URING ACTIVITY tion
( C) N
(cma
O d k hl) (cmr OdIg hl
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ACTIVITY M ETABOLISM I N A LIZARD
TABLE
INCREMENTS ABOVE PRESTIMULATION
LEVELS
DURING MI
STIMULATION AND
MIN
OF RE OVERY I N
L ' S ~ ~ ~ ~CCIDENTALIS
Inc r emen t Increment
during during Change in
Temp.
St imu la t ion
Recovery
Inc re me nt R e c o v e 0
( C)
( c m J
O r l k h l ) cma
O z l k h l ) ( c m a
O r l k h l )
Nore.-Values shown are means of 5-8 animals.
stricted at low body temperature: no
costal movements are evident during
Lactate formation
the bout of bu rst a
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7
ALBERT
P BENNETT
AND TODD T. GLEESON
blood most rapidly at 35
C
All of these
iguanids have preferred thermal levels
of 35-38 C The interrelationships of
oxygen debt, lactate elimination, and
recovery in reptiles have not been
examined, however, and it would be
premature to speculate about their
interdependence or physiological signifi-
cance.
2 5
The delay at low b
in achieving maximal
consumption is not
pected, considering the
logical systems involve
port. A similar lag ha
reported for the marin
rhynchus crist tus Be
The low oxygen con
Sc eloporu s occidental s
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ACTIVITY XETABOLISM IN A
LIZ RD
TABLE
3
WHOLE-BODY LACTATE CONCENTRATIONS
OF
SCELOPORUS
OCCIDENTALIS BEFORE DUR-
ING,
AND
AFTER SPECIFIED
PERIODS OF
AC-
TIVITY
AT
35 C
Lactate Concen tra t ion
Condition IV h s s
w t )
Unstimulated. 4 0.40+0.04
min active..
4
1.34+0.16
2
min active.
4
1.73 0.10
5 min active. .
4
1.70_+0.25
5 min active+
5 min recovery. 6 1.82f 0.08
NOTE.-Valueshown are means+SE.
temperatures in active Scelopmus is not,
examining aerobic wo
aerobic increment duri
The thermal depend
activity metabolism in
more complex than wa
posed. A low temper
over a wide range of b
was postulated on the
tions on whole-body
(Bennett and Licht 19
lactate concentrations
Bennett et al. 1975). T
of whole-body lactat
narrow thermal increm
and Dipsosaurus (Ben
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c e l o ~ o r u soccidentalis
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ACTIVITY METABOLISM I N LIZARD
hydrate catabolized enters anaerobic
pathw ays see Be nn ett e t al. 1975).
Energetic ou tpu t during burst ac tivity
is maximal over th e range of 30-35 C in
S.
occiderttalis. Body temperature of
animals in the field appears to have
some seasonal lability over this range
McGinnis 1966). Groups of anim als
caugh t in th e field during spring through
fall have mean body temperatures of
34.3-35.9 C. A similar group of winte r-
active animals, however, had a mean
body temperature of 30.4 C. All groups
tested in the laboratory had preferred
Sceloporus, in spite
Dipsosaurus is 2-3
Maximal anaerobic en
almost identical in the
production occurring a
rus and 40 C in D
output is maximized
modes at preferred b
40 C, in Dipsosaur
output is consequent
species 52 vs. 40 pmo
this increment is as
sup po rt of m uscular a
locom otory efficiency
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76
ALBERT
F BENNETT A N D TODD T
GLEESON
D A W S O N .
R .
1975. On the physiological signifi- cidentalis. Comp. Biochem
cance of the preferred body temperatures of rep-
FR Y F.
E
J 1947. Effects
tiles. Pages 443-473
i n
D. M. GATES nd R.
B
animal activity. pu b. O
SCHMERLds. Perspectives in biophysical ecol-
8:1-62.
ogy. Springer-Verlag New York.
D A W S O NW.
R.
and G. A. BARTHOLOMEW.956.
Relatio n of oxygen cons um ption to body weight
temperature and temp erature acclimation in
lizards
Uta slansburiana
and
Sceloporus occi-
dentalis. Physiol. 2001. 29:40-51.
DEWCAS.F.. and T S HART.1957. Use of th e Pau l-
M c G r N ~ r s N 1966. Scel
ferred bod y temp era ture
lizard. Science 152 : 1090
IMOBERLY . R. 1968a. The
the common iguana
Igu
under restraint. Comp.
ing oxygen analy zer for measu remen t of oxygen
consum ption of an imals in open-circuit system s
19686. T h e metab ol
and in a short-lag closed circuit apparatus
mon iguana Igztana igzc
J
Appl. Physiol. 10:388-392.
ing. Com p. Biochem. Ph
FRANCIS . and G. R . BROOKS.970. Oxygen con-
WILSON
K. J
1974. T h e
sump tion rat e of heart beat and ventilatory
supply for act ivi ty to bo
rate of parietalectomized lizards
Sceloporzrs oc-
species of lizards. Copei