1999

Asiatic Herpetological ResearchVol. 8, p. 81

Food Consumption and Growth of Juvenile Chinese Soft-shelled Turtles(Pelodiscus sinensis) in Relation to Body Weight and Water Temperature
CUIJUAN NlU, TlNGJUN ZHANG AND RUYONG SUN
Department of Biology. Beijing Normal University; Beijing 100875, China

Food consumption and growth of juvenile Chinese soft-shelled turtles {Pelodiscus sinensis) withbody weight were measured in the laboratory at 22, 26, 28, 30, 32 and 35 °C. At 30 °C, the daily=maximum consumption C max (J/ind. day) showed the following relationship with body weight(g): C max

Abstract.differentW•

47.58 W^.

The correlation between the maximum daily food consumption rate R max•(J/gday) of a turtle

with a standard body weight of 40 g, and temperature could be described as: logR max = -0.01 36T 2 + 0.8372T 1•

1.42. At ± 31 °C. a turtle with a standard body weight of 40 g has the biggest daily consumption rate of 447 J/g

The daily growth rate GR (g/day) had a functional relationship with body weight at 30 °C: GR =day.

0.04

W

8 - 48-.

For a turtle with a standard body weight of 40 g, GR showed the following relationship with water- 3.671T + 0.147T 2
temperature: GR = 30.138"0.002T 3 and at 30 °C, turtles had the biggest daily growth rate,of 1.06 g/day. Gross conversion rate of the juvenile
temperature had a distinct effect on it.

turtles(9-109 g) did not vary with body weight, but

Key words.- Reptilia, Testudines, Trionychidae, Pelodiscus, China, bioenergetics.

Introduction

30, 32The Chinese soft-shelled turtle (Pelodiscus sinensis)
an aquatic chelonian of great commercial importance, widely distributed in China. Resource of thisisand 35 °C). The photoperiod was 12L:12D.

Turtles were fed to satiation twice a day at 8:00 and
16:00. Each turtle was acclimated at the test temperature for at least one week before the feeding experi-ment started.

species has decreased sharply in recent years. There-aquaculture has become more and more
important. Basic information on the biology of P. sinfore,

its

ensis is very important in developing the technologyof its cultivation. Bioenergetics of this species is one
aspect that has not been well-studied yet (Niu et al.
1994). The purpose of this study was to investigate theeffects of body weight and water temperature on foodconsumption and growth of juvenile soft-shelled turtles.

Experimental process
Before thestartof the feeding experiment, turtles

were not offered food for 48 hours and weighted. In
the experiment, turtles

were fed to satiation with apre-weighted amount of food. The uneaten portionand feces were collected with a decompression concentrition equipment and dried with control diet at 65°C to a constant weight. Food consumed by a turtle

was the difference between the dry weight of preweighed amount of food and the uneaten portion. The
feeding regime lasted for a month followed by two

Material and Methods
The experimental animals were juveniles with a live
weight ranging from 7 g to 1 12 g reared in the laboratory. The diet used in the experiment contained 50%days of fasting. After the experiment, fresh weight
was measured again and some of the experimental
animals were sacrificed and dried to a constant weightcrude protein, 3% crude fat, 9.5% carbohydrate andon 65 °C. Caloric value of the dried diets, feces, and

15% ash. Energy value of the diet was 14.64 KJ/g.

turtles

wereallmeasured with a Schimdzu CA-4P

caloric meter.

Rearing conditions
Each experimental animal was housed in a 4.6

1glassData analysis

aquarium filled with clean tap water. 6-8 aquariums
were placed in a water bath with water temperature

The daily maximum consumption, C max is an averagecontrolled to an accuracy of ± 0.5 °C. The animals
were tested at six different temperatures (22, 26, 28,C max/W. W is the mean value of the initial and final

value during the whole experimental period.

weight of theturtle.

R^^ =The daily growth rate in wet

Vol. 8, p. 82

Asiatic Herpelological Research 1 999

3.6
22

y = -0.01 36x + 0.8372X - 1 0.8 r = 0.83

• Standard value

2.6-°

oo

0.6

Measured value—r~—3040

20i

Temperature (°C)
Figure 1. Relationship between the daily maximum consumption rate. R max (J/gday) of a turtle with a standardof40
valueofall
body weightg (averageexperimental animals) and water temperature.

weight,GR = (W, _ W)/t,where W, andW

istheend and the beginning of the
body weight
experiment, respectively, and t is the experimental
attheperiod. The gross conversion efficiency, CE— namedthe biggest daily food consumption rate of 447 J/g•day. The daily growth rate, GR (g/day) also had abody weight and water temwhich
could
beshowed as the following: GR
perature,close relationship withas the percent of energy used for body growth to con-= 0.0165W + 0.9142T - 0.0156T2 " 13.16 (r = 0.89,sumed energy
was calculated. All data were analysed with SPSS/PC statistical software.

n = 45, P < 0.01).

—

Results
Analysis of covariance showed that the maximum
food consumption of a turtle was greatly affected bybody weight and water temperature. Multiple regression

analysis

showedthefollowing

relationships

among the daily maximum consumption, C max (J/ind.day), wet body weight,

T0.0136T

W(g) and water temperature,logC max = 0.73381ogW + 0.83541ogT -(°C):

Figure 2 shows the relationship between the daily

growth rate, GR (g/day) of a turtle with a standard
body weight of 40 g and water temperature. At 30 °C,

2 "1

1.00; (r = 0.98, n = 45, P < 0.01). At 30°C, C max (J/ind.- day) showed the following relation-ship with body weightW

C max = 47.58W 7907-(g):;

a turtle with a standard body weight of 40 g has thebiggest daily growth rate of 1.06 g/day. At 30 °C,
had a functional relationship with body weight as:

GRGR= 0.04W08248 (r = 0.78, n = 39). At five different
body weight groups ranging from 9-109 g, no distinct
differences were found among their gross conversion

CE (F4,20 = 0.96, P > 0.05), but the temhada distinct influence on CE (F5.20 = 4.21,peratureefficiency,

P < 0.01 At 22 °C, CE was about 59%. At 26-32 °C,
CE ranged from 21-27%. At 35 °C, CE declined to).

12%.

(r = 0.92, n = 30).
Figure 1 shows the relationship between the daily
maximum consumption rate, R max (J/g day) of a tur•

tle with a standard bodyweight of 40 g (average valueof all experimental animals) and water temperature.
Their relationship could be described as: logR max = 2

0.0136T + 0.8372T - 1 1.42 (r = 0.83, n = 45). At ±3 1 °C, a turtle with a standard body weight of 40 g has

Discussion
According to the present work, temperature has a posmaximum food consumption

itive effect on the dailyand growth under 3 1 °C, but above 3 1 °C, the effectbecomes negative. Temperature for maximum growthrateisslightly

lower than the temperature for maxi-mum food consumption. This phenomenon has also
been observedin similar studiesof the lizards Uta

Asiatic Herpetological Research

1999

Vol. 8, p. 83

r' = 0.99
y = -0.0019x + 0.1469x -3.6708x + 30.138
23v2P2O

Temperature CC)
Figure 2. Relationship between the daily growth rate,

GR (g/day) of a turtle with a standard body weight of 40 gand water temperature.
stansburiana (Waldschmidt et al. 1986) and Takydro-

showed that under 109 g body weight, CE values ofmus septentrionalis (Ji et al. 1993), and the southern

the juvenile turtles

catfish (Silurus meridionalis) (Xieand Sun 1992).

This study indicates that effects of temperature on
food consumption and growth of soft-shelled turtles

were similar. Temperature has adistinct effect on CE. The relatively highCE (59%) at

22 °C may be explained by the distinctly low meta-

resemble that of most fishes (Brett and Groves 1979)

From 26-32 °C, CE
was relatively similar, but declined at 35 °C. Smith etand some lizards. More comparative studies should beal.

conducted for other reptile species.

The body weight has a double logarithm relationship with C max and the slope of the regression line is,0.79. This valueisvery similar to the exponent b

metabolic rate to body weight
lineforturtles(Bennett and Dawson 1976).
regression
value

0.75

in

thebolic cost at a low temperature.

(1981) found that for juvenile walleye pollock(Theragra chalcogramma), CE was higher at coldertemperatures. Cui et al. (1995) showed that water temperaturehad noeffect(Ctenopharyngodononidella).

CEinthegrass

carp

Perhaps the relationshipof temperature with CE varies with different species.
In

thiswork we present mathematical models

This phenomenon suggests that food consumption isrelating maximum food consumption and growth rate

related to metabolic rate of the turtle. As energy loss

to water temperature and body weight. The results canthrough metabolism is a large component in theenergy budget, metabolism level may affect energy

be utilized for estimating daily amount of food needed

intake to remain an effective budget. Studies on thebody weight in a turtle-culture farm.

by juvenile turtles according to water temperature andrelationship of food consumption and metabolic rate
arerecommended. Perhaps the maximum consump-tion rate can be defined as an index of daily

metabo-lism level of the animals.

The gross conversion rate, CE is a reflection of theconsumed energy alloted to body growth. Our work

Acknowledgments
We thank Mrs. Xihuang Cheng for her assistance inthe experiments. Thanks are due to Dr. Balazs Farkas
for improving the manuscript. We also thank Dr. Yibo
Cui for his valuable comments on the paper. The work

Asiatic Herpetological Research\999

Vol. 8, p. 84

was supported by the Chinese National Foundation of
Natural Science and the Foundation of State Key Laboratory for Freshwater Ecology and Biotechnology ofChina.

Zhang and R.Y Sun 1994. Energy
metabolism of the soft-shelled turtle Trionyx sinensis
Niu, C.J., T.J.

— Aquatic

respiration, relative to body weight andwater temperature. Journal of Beijing Normal University 30:536-539.

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York.

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