Microcalorimetric investigations of the energy metabolism of some reptiles

ThermochzmzcaActa,

94(1985)

161

161-167

ElsevierSciencePublishersB.V.. Amsterdam

MICROCALORIMETRIC

INVESTIGATIONS

- Printed

OF THE ENERGY METABOLISM

I.H.D. LAMPRECHT' and F.-R. MATUSCHKA' 1 Institut fiir Biophysik, Freie Universitat D-1000 2

Berlin

Institut

in The Netherlands

Berlin,

OF SOME REPTILES

Thielallee

63,

33 (Germany)

fur Angewandte

Haderslebener

StraBe

Zoologie,

9, D-1000

Freie Universitat

Berlin,

Berlin 41 (Germany)

ABSTRACT Energy metabolism of 16 lacertide lizards and 12 snakes was investigated by Heat production is compared with oxygen means of two Calvet microcalorimeters. consumption, rendering a value near to the theoretical value (19.3 J/ml oxygen) predicted for food mainly composed of lipids and proteins. Electrical stimulation of some of the experimental lizards and snakes showed burst-off behaviour and a strong increase in anaerobic metabolism with a consequent compensation of the oxygen debt. The experiments are discussed in connection with the usual indirect calorimetry.

INTRODUCTION In recent years lizards tiles

no direct

and snakes.

All knowledge

has been derived

graphy)

of oxygen

piratory

calorimetric

of indirect

known to calculate

The aim of the present thermic

reptiles

under complete Reptiles

ano&iosis

(ref.4, ref.5).

As direct

heat production, the animals cal tests

ref.2).

is that the form of metabolism

must be

In

it is an ideal method

animal's

the ability

time was of special

to anaerobic

under stress without

the individual

this context

calorimetry

heat production

metabolism

interest

while escaping

to investigate

weight

of reptiles

is not bound to gas exchange

sacrificing

of poikilo-

anaerobic

(ref.3).

or hunting but detects

metabolism

them, as is necessary

and

to live

in

for biochemi-

(ref.6).

Therefore, aerobic

(ref.1,

resin

from gas exchanges.

for a certain

are able to switch

of repor polaro-

concentration

for several minutes

on the species,

temperature.

on

air) of so-called

the lactate

study was to investigate

depending

the environmental

stressed

metabolism

(Warburg manometry

(in the inlet and outlet

calorimetry

heat losses

have been performed

and anaerobic

measurements

face masks or by determining

blood and body tissue of animals The disadvantage

about aerobic

from respiratory

concentration

chambers,

experiments

it seemed worthwhile

metabolism

in lizards

to measure

heat production

of the Calvet type (ref.7). 00406031/85/$03.30

of aerobic

and snakes with a usual isoperibolic

0 1985 Elsevier Science Publishers

B.V.

and an-

calorimeter

162 METHODS

AND MATERIALS

Animals Calorimetric

experiments

were performed

on the following

lizards

- 4 Milos wall lizards (Podarcis milensis) - 2 Common wall lizards

(Podarcis muralis)

- 3 Sand lizards

(Lacerta agilis) ~lizards (Lacerta lepida) --

- 3 Ocellated

- 3 Libanon wall -1

lizards

(Lacerta laevis) ~(Lacerta viridis) ___-

Green lizard

and the following - 1 Smooth

snakes

snake

(Coronella

- 1 Balkan whip snake -10 Aesculapian The weight

(Coluber

snakes

of the animals

gemonensis)

(Elaphe longissima). ranged between

ratory reared and increased ing maintenance

austriaca)

their weight

have been reported

4 and 18 g. All individuals during

previously

the experiments.

(ref.8,

were

labo-

Details concern-

ref.9).

Instrumentation Heat production of 100 ml vessels duction

was measured at changing

in two Calvet microcalorimeters

temperatures

rates of several mW and fivefold

the recording

system

(Micrograph

ever, it had to be increased power-time

curves

production,

the calorimetric

signal

The calorimetric

of

was set to 2mV. How-

temperatures. integrated

folded with the instrumental

vessels

The obtained

to find the mean heat

time constant

were open to air or hermetically

oxygen

determination

in the air. Without continuously

BD5; KIPP & ZONEN/Delft)

at low environmental

heat pro-

rates the sensitivity

to 'desmeare"

(ref.10).

nected to a polarographic simultaneous

higher maximum

(P-t curves) were mechanically

in some cases

(SETARAMILyon)

from 18 to 35°C. With mean

sensor

(Monitor System,

of heat production

larger disturbances

by means of a peristaltic

sealed and then con-

BECKMAN/Irvine)

and decrease

of oxygen

for a

concentration

the air in the vessel could be exchanged pump or discontinuously

by a larger sy-

ringe. The animals calorimetric high voltages

were electrically

vessel.

an electrode

cream

smeared

on the animals.

voltage

of 30 V was sufficient

to keep it moving. "appropriate" electrodes.

stimulated

In oder to facilitate

(HELLIGE/Freiburg)

to cause an explosive

of the animal

extending

into the

and to avoid dangerous

as used for EEG and ECG was

With the help of the electrode

Prior to stimulation

position

by two electrodes the experiments

the voltmeter

cream a stimulating

movement

pulsed

of the animal and

was used to monitor

by means of the resistance

an

between the two

163 RESULTS Figure 1 exhibits and its "desmearing"

the P-t curve of a Milos wall lizard by the Tian equation

(Podarcis milensis)

(ref.10).

t P/mW

b

80

60

40

20

0

t/min

Fig. 1. Power-time curve (strong line) of a Milos wall lizard (Podarcis milensis) and the original signal (thin line) calculated by means of the -equation (see text). There are periods of high activity can be determined. zards and snakes

and of rest from which

included

in these

investigations

stimulation

experiments.

and minimum

rates of heat production

has recently Table

the basal metabolism

Table 1 shows the mean rates of heat production

A detailed

been reported

(ref.8,

analysis

except

of the result together

and the correlation

for all li-

those animals

to oxygen

used for

with maximum consumption

ref.9).

1

Mean weights m(g) and mean specific rates of heat production p (mW/g) with standard deviation (mW/g) at 25'C for the different lizards and snakes in these investigations (n = number of experiments)

P.milensis P.muralis L.agilis C.austriaca C.gemonensis t.longissima

108 26 50

4.18 t 0.24 2.05 f 0.13 7.91 * 0.44

2.01 f 0.43 2.56 f 1.00 1.46 t 0.12

19 18 49

7.41 * 0.45 9.20 f 0.29 14.06 f 3.79

0.51 * 0.29 0.59 t 0.42 0.73 t 0.26

164

Fig. 2. Power-time curve (structured line) and change of oxygen concentration with time for an Aesculapian snake (Elaphe longissima) at 25°C. Figure 2 compares crease

the calorimetric

in oxygen concentration

longissima)

at 25'C. The oxygen

as much information

naturally

bic degradation

of glucose

are less structured

consumption

occuring

lizards

from the vessel

does not offer

Fig. 2 shows that the

are mainly

run by anaero-

P-t curves of snakes

because of the lower locomotor for many

down to an oxygen

activi-

hours.

concentration

mainly

coefficient

to the expected

of lipids and proteins.

found values

of anaerobic

In the stimulation

sharply

fermentation experiments

After thermal Usually

if the oxygen concentration

equilibration

At very low oxygen pointing

to energy metabolism

the two-electrode

the resistance

with the electrodes.

for a

concentrations

to a predominant

con-

(ref.9).

vessel allowed

to those obtained between

it is in the MOhm range and dropped

the animal was in contact

the limits of

value of 19.3 J/ml oxygen

increase,

are similar

decreased

of 18.6 f 3.2 J/ml oxygen

and 20.4 & 5.8 J/ml for snakes; within

to move around and the P-t curves

determined.

signal. Moreover,

keep their normal metabolism

for lizards

the experimentally

trodes.

snake (Elaphe

In the present study the animals became more active and ap-

error these figures correspond

tribution

for an Aesculapian

the snakes did not move

below 16%. In most cases an oxycaloric

food composed

line) with the de-

as an integral method

down to lactic acid. Usually,

temperature

parently tried to escape

was calculated

(structured

bursts of activity

than those of lizards

ties. At their prefered Lacertid

(smooth slope)

as the calorimetric

non-stimulated,

of 16% (ref.11).

P-t curve

the animals

without

elec-

the electrodes

was

to some IO kOhms when

This was the moment

the voltage

165

. ..-12.5

i 0

20

60

10

80

t/h

Fig. 3. Simulation of an Ocellated lizard (Lacerta lepida) at 30°C for 30 s with 30 V. The area between the P-t curve and the extrapolated heat production (dotted line) corresponds to 22.9 J, the maximum deviation of the oxygen slope after stimulation to 1.1 ml oxygen. was switched response

on for 30 s leading

is seen immediately

rographic

to the burst of activity

in strong oscillations

signal due to the vehement

the slopes of heat production the thermal

inertia

of the instrument

nal of a short pulsed

heat production

to the level prior to stimulation. literature

consumption

20.8 J/ml oxygen

is specific

If the duration additional observed.

Figure 3 exhibits

is smeared

consumption

to the typical

(steepness

the obtained

in the

of slope) oxygen

value of

Further

to the burst-off

sig-

decline

described

this additional

of glucose.

Due to

exponential

to observations

by stimulation,

contributions

information

metabolism

will

(ref.12). of the stimulation

heat production Sometimes,

the animals

in oxygen

for the metabolism

and anaerobic

be given elsewhere

heat output

with an approximately

The

and pola-

after stimulation.

of the oxygen debt. Comparing

with the heat production

about the aerobic

of the animal.

consumption

In contrast

there is a quick response

and a slow compensation

movement

and oxygen

of the reptiles.

of the calorimetric

these longer

find a position

is increased,

by the burst-off lasting

in which

a linear dependence

behaviour

stimulations

on this duration are without

of the can be

effect

because

they touch only one electrode.

DISCUSSION Except (ref.13)

for one very early calorimetric no direct calorimetric

experiments

investigation

on a lacertid

lizdrd

are found in the literature.

There-

166 fore, it seemed

interesting

energy metabolism

calorimetrically

with those obtained

vestigations

concern

experiments.

In the present

which would

to compare

reptiles

from respiratory

that were much heavier

study it was necessary

not only fit into the calorimetric

find space to move around and have enough crease

in oxygen

concentration.

bolism and weight be compared;

motory

the P-t curves

activity;

taneously

when

heat production

(ref.4) to the energy output

naturally

The P-t curves exhibit dissipation

debt

bolism of the animals.

heat output.

consumption

activities

ties of snakes were As lizards lism strongly

depends

30°C (ref.8,

was observed

by temperature

meta-

to the basal meta-

heat production

under investigation

Within

due to the "temperament"

animals

temperature.

the locomotory

one species of the indiactivi-

(ref.8, ref.9).

their energy metaboIn most cases a para-

temperature activity

than the basal metabolism

and

and from

the locomotory

than those of lizards

with a flat optimum

ren-

to the total

for the lizards

for the snakes.

to poikilothermic

ref. 9). For lizards

that these

by anaerobic

activities

on the species

upon the environmental

are

and of low levels of energy

to 79% for P.muralis

found to be smaller

activity

only over a longer period oftime.

from 65% to 88%. In general

and snakes belong

bolic dependence

depends

simul-

metabolism

it can be assumed

of locomotory

differences

e.g. in E.longissima

size can

are measured

are sustained

of high activities

to 81% for C.austriaca

there are often considerable

between meta-

about the loco-

of anaerobic

The ratio of the mean to the minimum

This figure strongly

74% for C.gemonensis

fluenced

and oxygen consumption

about the contribution

from 68% for P.milensis

viduals,

render information

is compensated

periods

also

values agree quite well

(Fig. 1 and 2). The latter ones can be attributed

ders information

changes

relation

of different

(Fig.2). As the bursts of locomotory

not stimulated

bolism and that the oxygen

of 100 ml, but would

the problem of a fast de-

for animals

to the contribution

in the slopes of oxygen

occuring,

Most in-

(ref.2).

of the reptiles

they allow deductions

never reflected

vessels

the limits of error the observed

with those cited in the literature Moreover,

measurements.

to chose small specimens

air without

figures

levels of

than those used in these

By means of the allometric

(ref.1) the obtained

within

determined

slightly

above

is more strongly

indicating

in-

that at lower tem-

peratures

the animals move more often or for longer times to find a place of

preferred

temperature

As direct processes trically

(ref.8).

calorimetry

in the absence stimulated

tric response

is a suitable

of gas exchange,

burst-offs.

heat production

area between

equals

to monitor

special

These burst-offs

(Fig.3) with a subsequent

getic level. The additional polated

means

attention

metabolic

was paid to elec-

showed an immediate

exponential

decrease

the observed

a stimulated

anaerobic

calorime-

to the former ener-

P-t curve and the extra-

heat production

of 22.9 J. As it

167 was provoked within

30 s i't corresponds

to an additional

higher than the value of 22 mW prior to stimulation, values

amount

servations

to 100.1 mW/g and 2.89 mW/g,

of Cragg

proximately

The results

movements

and attains

which

the larger volume

nel to the polarographic of oxygen

consumption

cate that an immediate the chosen

experimental

Direct calorimetry metabolism

of lizards response

that it takes apits usual,

in oxygen

consumption

of the slope changes 20 min. The time

as well as to the instrumental

retards

vessel

setup in

and the small connecting

the signal.

and snakes

Parallel

chan-

investigations

in a larger container

in the oxygen consumption

conditions

(ref.9) indi-

rate is observed

under

(ref.l2),

proves to be a suitable

of poikilothermic

other methods

observed

the steepness

of the calorimetric electrode

from 7.06 mW/g

with

a new steady state after approximately reasons

specific

vessel.

Nevertheless,

lag may be due to physiological

animals

tooi in the investigation

to render information

and to avoid the sacrifice

of the animal

of the

not obtainable

for anaerobic

by

analyses.

REFERENCES 1 2 3 4 5 6 7 8

A.F. Bennett and W.R. Dawson, in C. Gans (Ed.), Biology of the reptilia. Academic Press, London, vol 5A/3, 1976, pp. 127-223. A.F. Bennett, in C. Gans (Ed.), Biology of the reptilia. Academic Press, London, vol 130/3, 1982, pp. 156-199. D.A. Belkin, Science NY 139 (1963) 492-493. A.F. Bennett and P. Licht, J. Comp. Physiol. 81 (1972) 277-288. A.F. Bennett and P. Licht, J. Comp. Physiol. 82 (1973) 351-360. A.F. Bennett, R.B. Huey and H. John-Alder, J. Comp. Physiol. B154 (1984) 113-118. E. Calvet and H. Prat, Microcalorimetrie - Applications physicochimiques et bioloaiaues. Masson et Cie, Paris, 1956.

F.R. Matuschka and I.H.D. Lamprecht, submitted 9 I.H.D. Lamprecht and F.R. Matuschka, submitted 10 W. Hemminger and G. Hoehne, Grundlagen der Kalorimetrie. 11 12

13 14

fold

agree with ob-

of L.viridis

to recover and to continue

is not as promptly

(Fig.3).

results

Fig. 3 indicates

stimulation.

in the calorimetric

of stimulation

as in heat production immediately

at maximum

40 min for the animal

non-stimulated

The corresponding

resp. These

(ref.14) who found a stimulation

at rest to 173.7 mW/g

power of 763 mW,35

Verlag Chemie, Weinheim, 1979. B. Nielsen, J. Exp. Biol. 39 (1982) 107-117. I.H.D. Lamprecht and F.R. Matuschka, submitted L. Krehl and F. Soetbeer, Arch. Ges. Physiol. 77 (1899) 611-638. P.A. Cragg, Comp. Biochem. Physiol. 60A (1978) 399-410.