G une 1995

Asiatic Hcrpetological ResearchVol. 6, pp. 151-156

Studies on the Physiological Ecology of Incubation in Chinemys

reevesii

Eggs
pei-Chao Wang, Wei Ma, bo lu and wen-Hui you
Department of Biology, East China Normal University, Shanghai 200062, China

Abstract: -The length of incubation period in Chinemys reevesii eggs is 66.91±3.70, 62.29±9.00 and56.57±2.85 days at 28°C, 30°C and 33°C, respectively. The values of effective accumulative temperatureapproximate to a range of constant (1871 to 1903 C-day) during different incubation temperatures. The massof eggs buried in wet sand through incubation increased slightly about an average 0.48% to 3.66%. The massof turtle hatchlings just after hatching at 28°C, 30°C, and 33°C averaged 59.76±6.85%, 59.12±5.33% and56.3115.36% of pre-incubation egg mass, respectively. The total lost rate of energy substances increased
with the temperature of incubating and lost 25.9219.67% at 28°C, 32.5616.77% at 30°C, and 34.3515.67%
at 33°C. The metabolic rate of C. reevesii eggs was measured through incubation at 28, 30 and 33°C. The
pattern of metabolic rate of embryonic development in C. reevesii is peaked, similar to the conditions of someother fresh water turUes. Maximum VO2 occurred when its incubation is 65% to 80% of total incubationTotal

V0 2 of C. reevesii eggs was 94.61 mL/g at 28°C, 112.88 mL/g at 30°C and 152.22 mL/g at

Key Words:

Reptilia, Testudines, Chinemys reevesii, incubation period, hatchlings, effective accumulativetimes.

33°C.

temperature, oxygen consumption.

Methods and Materials

Introduction

The metabolicrateof developingin reptiles reflects the energetic

embryosdemands of both growth and maintenance(Wang et al., 1988). The ontogeny ofembryonic metabolic rate in reptiles has beenshown to have three patterns (Thompson,1989). The metabolic rate during most of
the incubation period has been reported inseven species of snakes (Clark, 1953;
Dim'el, 1970; Black et al., 1984), tenchelonians (Lynn and von Brand, 1945;
Ackerman, 1981a; Thompson, 1989;1984), three crocodilians(Thompson, 1989; Whitehead 1987), andone lizard (Wang et al., 1988). So far, that

Gettinger et al.,Fresh eggs of the turtle (Chinemysreevesii) were collected in the morning, after
being laid in the sandbox of the turtle farmnear our University. When each fresh egg

was removed from the sandbox on the dayof laying, it was marked and weighed with atorsion balance (±0.01 g) to determine thefresh egg mass. A total of 350 eggs wereexamined and divided into three groups inwhich the eggs of each group were buried ina dish of moist sand and incubated atof 28, 30 and 33°C
The
relative humidity of sandrespectively.
in the dish was maintained at a range of 98to 100%.

temperaturesof the common turtle (Chinemys reevesii)
has not been reported.
Ecological and heat energy metabolicThe,determinationofoxygen

consumption of eggs in C. reevesii during
the period of incubation was carried out withand closed system
was described by Wangstudies on adult turtles (Chinemys reevesii)ahave been reported before (Wang and Lu,respirometer that

1985; Wang et al, 1988). In this paper, we
will attempt to deal with the length of theincubation period and the metabolic rate ofDuring determination, the ambient
temperature also identified with theincubation temperature of each group. The

embryonic development inside the eggs ofChinemys reevesii in relation to ambient
temperature from July to September, 1988
and 1989.

experimental period was limited at 8:30 to10:30 in the morning and each experimentlasted an hour with recording every fiveminutes. The carbon dioxide (CO2) wassmall,simple(1986).

absorbed by© 1995 by Asiatic Herpetological Research

10%

NaOH solution. The

Vol. 6, p. 152

Asiatic Herpetological Research

April 1995

TABLE 1. T-test on differences of mean times from incubation to hatching in C. reevesii eggs at 28°C,30°C, and 33°C
Tjncub. - C

Different values (days)

28 v. 30
28 v. 33
30 v. 33

10.34

4.63
5.71

18.37

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Asiatic Herpetological ResearchVol. 6, p. 153

TABLE 5. A comparison between the mass of pre-incubation eggs and one of C. reevesii hatchlings during
incubation at 28, 30, and 33°C.

Incubation

Asiatic Herpetological ResearchVol. 6, p. 154

TABLE 6. Equations relating VO2 (ml/g-'day"
incubation to hatching in C. reevesii eggs.

T-Before Peak1)

to incubation days, total VO2, andApril 1995

VO2 of peak during

June 1995

Asiatic Herpetological Research

The average values of those were taken by ttest and the results of those exhibited nosignificant differences (Table 3), in otherwords, the values of effective accumulative

temperature for the embryonic developing
inside the egg of C.
reevesii areaofconstant
approximately
range
duringdifferent incubation temperature.

Changes of Incubating Egg Mass
During incubation, C. reevesii eggs
in wet sand (RH, 98-100%)
increased slightly in mass (Table 4). Thismay be due to the intake of water throughthe egg shell from the substrate (wet sand)and egg shell type.
buriedOn changes of egg mass (weight) in C.
during incubation which areconsidered due to a net water intake fromsurroundings or of export. For an egg toabsorb water, the potential of water insubstrate must exceed the algebraic sum of
reevesiipressure potential and the osmotic
potential of the egg contents (Packard et al.,1977). So that the viable egg contacting wet
substrates experienced net increases in mass
during incubation, that reflects on net fluxesof water across its egg shell (Packard et al.,
1977, 1982, 1985; Gutzke and Packard,1987). The egg shell type of C. reevesii is athehard shell, so the water contents of intake
from its wet substrates must be controlled orlimited to its egg shell type.

Vol. 6, p. 155

The losses were 25.92+9.67%
28°C, 32.56±6.77% at 30°c and34.75±5.67% at 33°C (Table 5).

incubation.
atPattern and Rate of Metabolism

The ontogeny of embryonic metabolic
been reported with three patterns:
peaked, sigmoid and exponential. The eggsof C. reevesii during incubation at threedifferent temperatures had an extreme
peaked pattern of oxygen consumption,
similar to the conditions of some fresh water
turtles (Gettinger et al., 1984; Lynn and vonBrand, 1945; Thompson, 1989; Webb etal., 1986), Crocodylus (Whitehead, 1987),
Alligator (Thompson, 1989), and somebirds (Vleck et al, 1980) but different frommany other reptiles (Ackerman, 1981; Blacket al., 1984; Clark, 1953; Dmei'el, 1970;
rate has

Wang et al., 1988).
The patterns of embryonic metabolic
ontogeny appear

to be

associated withdifferent patterns of growth, egg shell types

and environmental conditions of incubation(Thompson, 1989; Whitehead andHowever, peaked orof
sigmoid patternembryonic metabolic
bedue
to the fact that theontogeny maySeymour, 1990).

energy expenditure for embryonic growth isdecreased as the growth rate of embryo inlate incubation period declines. This canpossibly facilitate synchronous hatching in
clutches.

The Ratio between Mass of P re-incubation

Acknowledgments

Egg and of Hatchlings
ThisThe mass of C. reevesii hatchlings justafter hatching at 28°C, 30°C and 33°C
averaged for 59.76%, 59.12% and 56.37%
of pre-incubation egg mass (Table 5),
respectively. The values of those were less25.64%, 26.28% and 29.03% less thanstandard rate of pre-incubation egg mass(Table 5). However, the algebraic sum formass of egg shell and of hatchling just after
hatching in C. reevesii is also less than one
Thisof pre-incubation egg (Table 5).
insubstances
thataofenergy
suggests
partincubation.
islostor
consumed
throughegg
The total lost rate of energy substances
increased with the temperature of

Scientificwork was supported by theFund of the State Educational

Committee of China and East China NormalWe would like to thank Dr.
Muth and Dr. Gary C. Packard forproviding some literature, and also thankDr. M. B. Thompson for comments on themanuscript and Professor Ermi Zhao forUniversity.

Allan

helpful discussion and encouragement.

Vol. 6, p. 156

Asiatic Herpetological Research

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