1999

Asiatic Herpetological ResearchVol. 8. pp. 48-52

Correlations of Reproductive Parameters of Two Tropical Frogs from Malaysia

Ibrahim H. Jaafar

1,

Ahmad Ismail 2 and Abd-rahman Kurais 2,

Biological Sciences Program, School Of Distance Education, Universiti Sains Malaysia, 11800, Minden,

Penang, Malaysia. "Department of Biology, Faculty of Science and Environmental Studies, Universiti Putra
Malaysia, 43360. UPM, Selangor, Malaysia.

A study on the relationships of reproductive parameters such as fecundity, egg size, clutch weight andbody size of two frogs, Rana cancrivora (Gravenhorst) and R. limnocharis (Boie), from Malaysia was carriedout in February 1992. The results showed that all the parameters quantified were greater in R. cancrivora than in
R. limnocharis. No correlation was found between the spawned clutch size and egg size for both species.

Abstract.-

However, correlation analyses of unspawned clutch showed that there exist positive relationships between female
size and clutch size, female size and clutch weight, female size and egg weight, clutch size and clutch weight,
and clutch weight and egg weight in R. cancrivora. For R. limnocharis positive correlations were found between
clutch size and clutch weight, and clutch weight and egg weight for the unspawned complement. The advantages,

non-advantages, correlation and non-correlations of these parameters with respect to their reproductive strategies

and success of these frogs are discussed and compared with the current information from the literature.

Key words.- Aiiura, Ranidae, Rana cancrivora, R. limnocharis, Malaysia, reproductive parameters, female size,
clutch size, egg size, clutch weight, egg weight.

Introduction

species, while four species of frogs

The fecundity or clutch size in amphibians is highlymode(Salthe,on body

and reproductive
1969: Salthe and Duellman, 1973:

variable depending

size

Kaplan, 1980). As a general rule, large species pro-

duce more eggs than smaller ones and species thathave generalized reproductive modes have larger
clutches than those with specialised modes (Duellman

and Trueb, 1986). The fecundity and hatching successof an amphibian population play an important role in
the propagation and future survival of the population(Ibrahim and Ahmad, 1992). Reproductive success ofa female depends upon the number of eggs produced

and their quality, but are constrained by physiologicalcapacities of the female and the trophic quality of theenvironment (Rafinska, 1991). The number of eggs
deposited by amphibians varies greatly from species
to species

andthis large disparity in fecundities is

explained by differences among amphibians in sizesof eggs, patterns of development, sizes of females andreproductive behaviour (Porter, 1972: Salthe andDuellman. 1973: Kuramoto, 1978; Kaplan, 1980).

Studies on the fecundity of temperate frogs have generated considerable data on this facet of amphibian

reproduction (Collins, 1975: Kuramoto, 1978; Duellman and Trueb, 1986), but information on tropicalfrom Malaysia

also showed differences in fecundities both between

and within species (Ibrahim and Ahmad, 1992). Inger
and Bacon (1968) found that four large ranids in
Borneo have clutch sizes in excess of a thousand eggs,
while Yorke (1983) reported that the average clutch
size for a rhacophorid in Malaysia to be 225 eggs.

Ovum size is another important aspect of anuran
reproductive biology. Large ovum size is generally
associated with large female body size and thus
directly hints of better fitness and survival value. Egg

size variability in amphibians has been interpreted as

adaptive since, where breeding habitats vary unpredictably, production of a wide range of sizes may

enhance adult fitness more than does the output of asingle 'optimal' egg size (Tejedo and Reques, 1992).

The egg size of numerous temperate anurans are well
documented in the literature (e.g. Salthe, 1969; Salthe
and Duellman, 1973; Bell and Lawton, 1975; Collins,
1975; Kuramoto, 1978; Jorgensen, 1981; Duellman
and Trueb, 1986; Reading, 1986; Rafinska, 1991;
Tejedo and Reques, 1992), but again however, only a

few reports concerning this parameter are available
for tropical species (e.g.

Liem, 1959; Alcala, 1962;

Inger and Bacon, 1968; Uchiyama et al., 1990).

Rana cancrivora (Gravenhorst) andoriental species are few and far between. Berry (1964)

cluiris (Boie) are

reported that seven anuran species in Singapore
exhibited difference in fecundities between and within

realm (Church,R.

limno-

two species of anura that have awide distribution across the oriental zoogeographical
Inger, 1966;

1960: Alcala, 1962; Berry 1964;
Kuramoto, 1978). In spite of this only a

1999

Asiatic Herpetological Researchhandful of information have been published concern-

fecundity). Thising the fecundity and size of their eggs (Alcala, 1962;(

Berry, 1964; Kuramoto. 1978). It is also evident fromVol. 8, p. 49

isa modified

Indomalayan frogs the eggs in the ovary are esscn
two size classes an enlarged or developing

the literature that there exist considerable variations intially in

the relationships of body size, egg size and fecundity

set and a much smaller,

within thelatterAmphibia(Salthc,

1969; Collins,

1975;

method of Kuramoto1978). Inger and Bacon (1968) reported that in most:contributes

white "undeveloped set'no significant portion

Kuramoto, 1978; Jorgensen, 1981; Reading, 1986;
Duellman and Trueb, 1986). This paper therefore

volume of the ovary.

determines the fecundity and egg size of both R. can-Results;

theto the total

crivora and R. limnocharis and then examines theexisting relationships in the reproductive parametersof both frogs.

Forty-two spawned batches of R. cancrivora eggs andthirty-four of R. limnocharis were collected from the

The Study Site

February 1992. These were investigated forfecundity and size of spawned eggs. In addition thirty-

The

two batches of R. cancrivora eggs and thirty of R. lim-

field inplace chosen for the study is a rice growing
region near the small town of Tanjung Karang (3°20'N. 101° 10'E), in the state of Selangor, elevation
about 3 m above mean sea level. It is situated about
100 km to the northwest of Kuala Lumpur, the Malaysian capital. Previously this area was a freshwater peatswamp forest which was opened up and converted to
paddy fields by settlers in the 1920's. Presently due tothe improved and upgraded irrigation and drainage
system, the farmers are planting two rice crops a year.

were

nocharis

obtainedfromsacrificed

gravidfemales.

The results showed that the average number of
eggs laid by R. cancrivora females from Tanjung
Karang is 1077.9 (sd = ± 238.97, range 662 tol677).
That for R. limnocharis 405.5 (sd = ± 92.45, range

233

to 657). Weighted t-test for unequal variance(Cochran and Cox, 1957) showed that the number of

eggs oviposited byR.

cancrivora

issignificantly

greater than that laid by R. limnocharis (t = 16.751, p

Material and Methods<0.001,df=74).

To determine the fecundity and egg size of spawned

mm (sd = ±0.091, range 1.16 to 1.53) while the mean
diameter of R. limnocharis eggs
1.15 mm (sd = ±eggs, newly deposited egg clutches of both species
were collected from recently innundated rice fields.

Breeding choruses were visited, amplecant pairs offrogs were located and their positions marked withwooden pegs. Male frogs usually start calling as soon
as dusk sets

and individuals of both species usuallymating as soon as the males begin clasping
the females. This usually occurs at around OlOOhrs or
initiated

0200 hrs. The pairs will then move into the flooded
rice paddy and egg laying will occur around 0500 hrs.
The number of eggs in each clutch were then recorded
and the eggs collected and preserved in 4% formalin
and kept in labeled, airtight plastic 40 dram bottles. In
the laboratory,

30 to 50 eggs from each clutch werethen randomly chosen and their diameters measured

under a stereo microscope with an ocular micrometertodetermine the mean size of eggs of each species.

All eggs measured were between Stages 3 and 9 ofGosner(1960).

To

investigate therelationship between

femalebody size and, (a) the number of unspawned eggs, (b)weight of unspawned egg clutch and (c) the weight ofunspawned eggs, the snout-urostyle length of gravid
females with large pigmented ova in the oviducts
were measured, the unspawned egg complement were

weighed (clutch weight) and counted (clutch size or

The mean diameter of R. cancrivora eggs is 1.35
is0.027, range 1.10 to 1.21). Again a weighted t-test forunequal variance showed that the egg size for both= 12.980, p <0.001, df =74). However, no correlation was foundisspeciessignificantly

different(tbetween the spawned clutch size and egg size for both
species.

For clutch complement of unspawned R. cancrivora eggs, the average clutch size was 2904.6 (sd = ±1600.6, range 889 - 7573), the average clutch weightwas 2.25 g (sd = ± 1.726, range 0.37 - 5.71) and theaverage egg weight was 0.75 mg sd = ± 0.257, range
0.28 - 1.35). The same parameters for R. limnocharis
was 702.6 (sd = ± 306.49, range 312 - 1659), 0.40 g
sd =(sd = ± 0.264, range 0.074 - 1.04) and 0.55 mg((± 0.249, range 0.237 - 1.01) respectively. Weighted tunequal variance on the clutch size, clutch
andweightegg weight between the two species
showed that these parameters were significantly diftests forferent (t= 7.634, p < 0.001, df = 60; t = 6.799, p <0.001, df =60; and t = 3.019, p < 0.05, df = 60 respectively).

Correlation analyses carried out on the reproduc-parameters of unspawned eggs for each species
showed that for R. cancrivora there is a positive corretiveVol. 8, p. 50

Asiatic Herpetological Research

1999

lation between female size and clutch size (p < 0.001,

ticular= 0.6333), female size and clutch weight (p< 0.001, r= 0.6867), female size and egg weight (p < 0.05, r =0.4073), clutch size and clutch weight (p < 0.001. r =0.8870) and clutch weight and egg weight (p < 0.001.
r = 0.5983). There was no statiscally significant corre-

Salthe and Duellman. 1973; Jorgensen, 1981). Thererenvironment

exists a positive(Pettuscorrelation

and Angleton,

between egg

1967;

size

and

hatchling size in frogs (Salthe and Duellman, 1973)

and a large metamorphic size is important because of
the interrelationship of body size, time of metamor-

lation between clutch size and egg weight. For R. lim-

phosis, age at first reproduction and fecundity ( Wil-nocharis however, there exists positive correlation
between clutch size and clutch weight (p < 0.001, r =bur, 1972; Wilbur and Collins, 1973; Doty, 1978).
Thus the observed larger egg size of R. cancrivora

and clutch weight and egg weight (p < 0.001,

over R. limnocharis could probabaly be assumed to0.7501r)= 0.6818)

no correlation was foundonly, while

between female size and clutch size, female size andweight, female saize and egg

clutchweight, andclutch size and egg weight.

The interspecific differences in the sizes of eggs in

The number of eggs oviposited by breeding femalesof both species were lower than that found in theiris

not unexpected because presumably

the breeding females were depositing the complementof eggs that were mature and retaining the unripe ones
for later oviposition
Inger and Bacon, 1968; Telford
and Dyson, 1990). It is likely that both females of/?.
(cancrivora and R. limnocharis in Tanjung Karang
may breed more than once during the breeding season. Wells (1976) concluded that one of the majoradvantages of a prolonged breeding period may be thecapacity for females to breed twice or more in a single
season. Hence it is possible that as a security measure
the females only release a portion of eggs from theirovarianThe

complement.

incidenceof

multiple

uncommon in amphibians and havebeen reported in anumber of anuran species (Collins,

clutchesisand could probably also be assumed to do thesame with respect to metamorphic size, post metadity,

morphic growth and age at first reproduction.

Discussion

ovaries. Thisconfer reproductive advantage with respect to fecun-

not1975; Howard, 1978; Perril and Danial, 1983; Telford
and Dyson, 1990; Rafinska, 1991).

Alcala (1962) and Uchiyama (1990) reported thatthe clutch size for R. cancrivora was probably

morethan 2000 and1800 eggs respectively. Our study
found a lower clutch size than these two. Berry (1964)

presented data on the number of ovarian eggs in Singaporean R. limnocharis. Calculations based on her
data gave the average clutch size for her samples as

576.4 eggs (range 266-1318). This is comparable toamphibians is well documented in the literature (Inger
and Bacon, 1968; Collins, 1975; Kuramoto, 1978;
Duellman and Trueb, 1986). For example. Collins(1975) found that there

significant difference inisaverage egg diameter between Hyla versicolor, R. sylvatica, Bufo americanus and R. catesbeiana, while forH. crucifer and Psuedoacris triseriata there was no
significant difference. Generally this reflects the great

variety in amphibian species with respect to egg pro-duction, reproductivemodes and other demographic

parameters (Salthe and Duellman, 1973; Kuramoto,
1978; Kaplan, 1980; Duellman and Trueb, 1986) as
well as the diversity of adaptations to the different
array of environmental selection and pressure. Phenotypic plasticity related to female age, size, trophic

conditions and genetic factors also contribute to theobserved egg size variationinamphibians (Berven,

1982; Rafinska, 1991). Hence it is not surprising that
there exists significant difference in egg size between
R. cancrivora and R. limnocharis in this study since,

as mentioned earlier, a number of workers have con-cluded that within a reproductive mode, the greater
the female size, the larger will be the ovum size
(SaltheandDuellman,

1973;

Kuramoto,

1978;

Kaplan, 1980).

For R. cancrivora in this study, there exist positive
correlations

femalebetween female

size

and clutch

size,

size and clutch weight, clutch size and clutch

the results of this study.

weight, and clutch weight and egg weight. Since bodysize is an indication of body condition, the high corre-

ancy could be due to the clinal effect within the spe-

(Reading, 1986). Other workers also found that there
is a positive relationship between clutch size andHowever, Kuramoto (1978)
clutchsize, clutch weight and egg
reported larger
forR.
limnocfiaris
from Japan. This discrepweightcies(Duellman

andTrueb,
since

1986)

or

even

the

geographical differences,
Japanese frog
would be at the northernmost edge of its distribution.

The difference in egg size between different different populations ofamphibian species have been

attributed to adaptation of the population to their par-lationbetween body size and clutch size is expected

female body size (Pettus and Angleton, 1967; Salthe
and Duellman, 1973; Collins, 1975; Howard, 1978;

Kuramoto, 1978; Banks and Beebee, 1986; Gibbons
and McCarthy, 1986; Reading, 1986). The positive
relationship between clutch size and clutch weight.

Asiatic Herpetological Research

1999

and clutch weight and egg weight in R. cancrivora isbecauseVol. 8, p. 51

of reproductive strategies, they are thus subjected to

speaking, thegreater the egg number, the greater will be the clutch

variousweight, and the greater the egg weight, the higher the
clutch weight. Kuramoto (1978) also found the sameThis

some of his Japanese anurans andsimilarly Reading 19861 found that there was a trend

witness to today.

as a whole in the population of British B. bufo for egg

Acknowledgments

weight, egg number and ovary weight to increase withfemale size.

The authors wish to express their gratitude to Univer-also

anticipatedphenomenon

generallyindifferences

environmentalinpressurestowhich they must adapt in order to survive and prosper.
thenmanifests

into

the

huge

variabilityofamphibian reproductive demography as what we are

(

siti

Collins (1975) reported that there was positive
correlation between egg diameter and female bodysize in R. sylvatica, H. versicolor and B.

americanusfrom Michigan. Banks and Beebee (1986) found thatsnout-vent lenght

isMalaysian Government for financing the project
under the Intensified Research in Priority Areas Grant.

The participation of IHJ was made possible through astudy grant from the Univcrsiti Sains Malaysia.

correlated with egg size in B.

calamita from England and suggested that this was, in

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