2004

Asiatic Herpetological ResearchVol. 10, pp. 298-305

Karyological Studies on Amphibians in China
YUHUA YANG
Molecular Biology Labortary, Department of Bioengineering, Sichuan University, Chengdu, 610064, R.P.China
Abstract. - Since 1978, 79 species of anurans have been studied karyotypically using conventional Giemsa staining
and various banding techniques. The chromosome numbers are 2n=22-64 and the karyotypes are variable. The homomorphic and heteromorphic sex chromosomes of some species have been identified.The mitotic and meiotic chromosomes of 14 species in two families of Urodela have also been investigated. The family Hynobiidae is karyotypically more primitive than the family Salamandridae.
Key words. - Karyology, amphibian, Anura, Urodela.

Introduction
Karyological studies of amphibians in China were pioneeered by two scholars. In 1952, famous cytologist T.
C. Hsu, an American of Chinese origin, developed the
hypotonic technique for chromosome separation andobservation. In 1956, cytogeneticist J. H. Tjio, a Swedeof Chinese origin, reported that the number of humanchromosomes is 46, not 48. In China, karyological studies of amphibians began in 1978. Ninety-three species ofamphibians have been studied so far, about 42% of the
220 living amphibian species in China (Table 1).
Changes of chromosome numbers. - Kuramoto (1990)
summarized the chromosome numbers of 983 species ofanurans from 21 families (2n=14-64). Chromosome
number changes occurred in 12 of 21 families with polyploids in some species. In China, the chromosome numbers of 79 species from seven families are 22-64 andvariations of chromosome numbers were found in four
genera, three families (Table 2).
Only two species in the family Discoglossidae havebeen studied: Bombina orientalis and B. maxima. Tianand Hu (1985) subdivided the genus Bombina into two
subgenera, Bombina and Glandula. Bombina (B.) orientalis has 2n=28 chromosomes (Zhao, 1986), consistent
with the chromosome number of Discoglossus pictus inEurope (Morescalchi, 1965; Schmid et al., 1987).
Bombina (G.) maxima has 2n=24 chromosomes (Jiang
et al., 1984), as reported by Okumoto (1974) andSchmid et al. (1987).
The geography of the Hengduan Mountain Ranges
greatly influence the evolution of pelobatid frogs, providing refugia for some species as well as discontinuous
population distributions that promote allopatric speciation (Yang et al., 1983; Hu et al., 1985). The pelobatids
distributed in the Hengduan Mountain region have distinct morphological differences adaptive to the unusual
geographic conditions. These species belong to two subfamilies, Megophryinae (Brachytarsophrys and© 2004 by Asiatic Herpetological Research

Atympanophrys) and Oreolalaxinae (Scutiger,
Vibrissaphora, Leptobrachium, and Oreolalax).
Available karyotypical information showed that species
studied have 2n=26 chromosomes, but karyotypical differentiations are prominent in the family. The subgenus
Vibrissaphora is the most specialized, all five species
have 2n=26, consisting of six pairs of large chromosomes and seven pairs of small ones, NF=52 and one
stable secondary constriction is located in 6q (in the
NoRs region; Zhao et al., 1983). The karyotypes of three
species in genus Scutiger are similar to those of subgenus Vibrissaphora, except the secondary constriction
located in 2P not in 6q. Polymorphic chromosome number occured in Oreolalax. Two of the three specimens ofO. schmidti are 2n=28 and one is 2n=26 (Zheng andWu,
1989). A similar phenomenon was found in O. liangbeiensis and C-banding showed that the extra pair ofsmall chromosomes is C-band negative and not B chromosome (Li et al., 1990). Polymorphic chromosome
numbers were also found in three genera ofMegophryinae. Wu (1987) observed one male triploid in
Atympanophrys shapingensis. Tan et al. (1987) reported
the karyotypes of Brachytarsophrys carinensis. Among
12 individuals examined, seven males and one female
have 2n=26, three males have 2n=27, and the remaining
male has 2n=28. The extra chromosomes are metacentric and between No.10 and No.11 in size. In addition,
there are four pairs of small chromosomes which aretelocentric in the2n=26 karyotype and two pairs of small
telocentric chromosomes were observed in M. omeimontis (Wu, 1987; Zheng and Wu, 1989).
The karotypes of pelobatids reported by foreignauthors are 2n=26, NF=52 with no polymorphic chromosome numbers found, except Leptolalax pelodytoides with 2n=24 (Morescalchi, 1973; Morescalchi etal. 1977; Schmid, 1980, 1987). It is interesting that a
special karyotype was observed in Rana phrynoides distributed in Hengduan Mountains. In this species, 2n=64
consisting of all telocentric chromosomes. Only one
homologous pair of NORs being found in interstitialVol. 10, p. 299

Asiatic Herpetological Research

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Table 1. A list of amphibian species studied karyologically.
FamliesNumber of
species Known

Number of
species studied

Number of
species Banded

Anura:
Discoglossidae
Pleobatidae
Bufonidae
Hylidae
Ranidae
Rhacophoridae
Microhylidae
Total anurans

4
46
13
6
77
32
14
192

2
18
4
4
35
7
9
79

0
12
4
1
24
3
4
48

Caudata:Hynobiidae
Salamandridae
Total caudates

17
17
34

7
7
14

0
2
2

segment of No.20 chromosome, i.e, position of the solesecondary constriction, and No.32 being sat-chromosomes (Liu and Zan, 1984; Wu and Zhao, 1984). This
karyotype is unique for anurans.
Karyological Studies on wood frogs in China. - In
China, wood frogs include five species (R. altaica, R.
amurensis, R. japonica, R. chaochiaoensis, and R.
chensinensis; Tian and Jiang, 1986). Rana chensinensis
had been called R. temproaria chensinensis (Pope andBoring, 1940; Liu and Hu, 1961). Wu (1981) reported
the karyotype of R. chensinensis from Beijing, whichhas 2n=24 chromosomes, including six pairs of large
chromosomes (relative length>7%) and six pairs ofsmall ones (relative length<6%), while R. temporaria in
Europe has 2n=26 (Guillemin, 1967), including fivepairs of large chromosomes and eight pairs of small
ones. Consequently, he suggested that R. chensinensis
should be a good species, not a subspecies of R. temporaria. Wei et al. (1990) compared the C-bands andNORs between R. chensinensis from type locality and R.
temporaria in Europe. As a result, in the former species,
centric C-bands located in Nos. 9 and 10 chromosomes
and telocentric C-bands in the terminations of a few
chromosomes, 28 interstitial C-bands, one pair of standard NORs in 11q, and small additional NORs arefound. However, in the latter species, both centric andtelocentric C-bands are located in all chromosomes andonly three interstitial C-bands and 1 pair of NORs in 10q
were developed (Schmid, 1978). Evidently, this comparison supports Wu’s suggestion.
Jiang et al. (1984), Luo and Li (1985) and Ma(1987) indicated that R. chensinensis from different
localities have the same 2n=24 pattern, but the numbersof subtelocentric chromosomes and the positions of secondary constrictionas are locality specific by comparing
the karyotypes of R. chensinensis from Beijing,

Qingdao, Lanzhou, Harbin, Hongyuan and Yanbei.
Consequently, it was suggested that R. chensinensis
might contain different subspecies .
The five species of wood frogs have 2n=24 or
2n=26 chromosomes and may be divided into twogroups: R. japonica, R. chaochiaoensis and R. amurensis belong to 2n=26 group and R. chensinensis and R.
altaica to 2n=24 group. The karyotypic differences
between two groups are listed in Table 3.
Rana japonica from Hiroshima, Japan has 2n=26
chromosomes, Nos. 8 and 9 are subtelocentric and thesecondary constriction is located in 9q; R. amurensis
coreana from Korea has 2n=26, Nos. 10 and 13 subtelocentric and secondary constriction in 9q; while R.
chensinensis from Hokkaido, Japan has 2n=24, No.11 is
subtelocentric and the secondary constriction in 10q(Nishioka, et al., 1987). Matsui (1991) described R.
chensinensis from Hokkaido as a new species, R. pirica,
based on morphometric and electrophoretic studies.
The No.6 chromosome of the species having 2n=24
is nearly the same in relative length as the sum of chromosomes No.11 and No.12 or No.13 of the species with
26 chromosomes, For instance, the average relative
length of No.6 chromosomes of R. chensinensis and R.
altaica is 8.19, while the average relative lengths of
Nos.11, 12 and 13 chromosomes of the other three
species are 4.52,4.31 and 3.82 respectively. In addition,
it is clear from Table 3 that there are more subtelocentric chromosomes and secondary constrictions in thespecies having 26 chromosomes than those in thespecies having 24 chromosomes, and they are concerned with small chromosomes. Accordingly, it isspeculated that all wood frog species would have a common ancestor, from which the species having 26 chromosomes were derived and the species having 24 chromosomes evolved via fusion of two pairs of small chromosomes of the former. Then, the species possessing

2004

Asiatic Herpetological ResearchVol. 10, p. 300

Table 2. A summary of chromosome numbers of 79 anuran species.
* = Polymorphic chromosome number occurs in some species.

Taxon
Discoglossidae
Bombina
Pelobatidae
Atympanophrys
Brachytarsophy
Megophrys*
Oreolalax*
Scutiger
Vibrissaphora
Bufonidae
Bufo
HylidaeHyla
RanidaeRana
Amolops
Ooeidozyga
Altirana
Rhacophoridae
Rhacophorus
Philautus
Polypedates
Microhylidae
Microhyla
KaloulaKalophrynus
Total

Number of species
22

24

26

28

64

Total

-

1

-

1

-

2

-

-

1
1
2
6
3
5

-

-

1
1
2
6
3
5

4

-

-

-

-

4

-

4

2

-

-

6

1
-

2
-

21
7
2
1

-

1
-

26
7
2
1

-

-

5
1
1

-

-

5
1
1

5

4
11

1
1
60

1
2

1

5
1
1
79

different subtelocentric chromosomes and secondary
constriction positions were developed into two groups
through inversions and translocations. The high resolution R-bands of R. japonica were prepared and analyzed(Heng, 1984), providing a practical technique for studying karyotypic evolution of amphibians.
Sex chromosomes and sex-determining mechanisms.The first successful demonstration of sex-determining
mechanism was made by making use of reversal andbreeding experiments (Humphrey, 1942, 1945, 1957).
The applications of cytogenetic techniques, such as Cbanding, quinacrine mustard staining, Ag-NORs staining and in situ hybridization of nucleic acids, have been
helpful to the investigations on sex chromosomes andsex-determining mechanisms in amphibians. So far,eleven species with cytologically detected sex chromosomes, including XY and ZW systems, even an OW/OO
system of sex determination and multiple sex chromosomes in one genome(Schmid et al., 1992) were discovered. Few sex-specific chromosome pairs in heterogametic individuals are heteromorphic and most of them
are homomorphic.

The homomorphic chromosome pair No.4 in Ranaesculenta was identified as sex-specific chromosomes of
XX/XY type by BrdU replication banding technique. All
males have an extremely late-replication band in thelong arm of Y, which is lacking in the X (Schempp andSchmid, 1981). The homomorphic chromosome pair
No.10 in Bufo gargarizans was demonstrated to be sex
chromosomes of ZZ/ZW type. The Z chromosomes inall males replicated synchronously, while Z and W chromosomes of females revealed heteromorphic replication
bands at the late replication stage. There was a replication band on W chromosome’s long arm and Z chromosome lacked the band (Wen et al., 1982;Shang andDeng, 1982). Similarly, the chromosome No.6 pair in
Bufo raddei was identified as XX/XY sex chromosomes(Deng and Shang, 1984) and the No.9 chromosomes ofRana nigromaculata as XX/XY sex chromosomes (Wuand Zhang, 1985). The sex chromosomes of species
mentioned above are homomorphic and could only berecognized by BrdU replication banding. So they are at
the initial stage of sex chromosome differentiation.
The Y or Z chromosomes of homomorphic sex
chromosomes in some anurans heterochromatinized soVol. 10, p. 301

Asiatic Herpetological Research

2004

Table 3. karyotypic comparison between wood frog groups.
Species

2N

Subtelocentric pair(s)Position of S.C.

R. japonica
R. chaochiaoensis
R. amurensis

26
26
26

No.7 or No.9
No.8 Nos.9,10,12,13

2-5p,6-7q
5-7p,8q,10p
8q

R. chensinensis (from type
locality)R. altaica

24

No.9

11q

24

--

1q

highly that they could be recognized by C-banding orother specific staining of constitutive heterochromatin,for example, the XX/XY sex chromosomes in genus
Triturus (Schmid, et al., 1979). Chinese scholars Wu andChen (unpublished data) determined the homomorphic
chromosome pair No.9 as XX/XY sex chromosomes in
Rana margaratae using C-banding and quinacrine mustard staining. There is one interstitial C-band, i.e, thebrightest fluorescense band, on both No.9 chromosomes
in females. The interstitial C-band is located only in one
No.9 chromosome, while one telocentric C-band in theother No.9 chromosome shows no fluorescense differentiation.
The first-discovered highly heteromorphic ZW typesex chromosomes occured in Pyxicephalus adspersus(Schmid, 1980). The W chromosome is much smaller
than Z chromosome and its short arm is completely heterochromatic. Wu and Zhao (1984) and Wu et al. (1987)
demonstrated that Amolops mantzorum has well-differentiated XY type sex chromosomes,the Y chromosome
is subtelocentric and mainly composed of euchromatin,but has strong C-band in the middle of long arm and X
chromosome is metacentric by conventional Giemsa
staining and C-banding methods.
Karyological studied in urodeles. - Only two species
were studied by C-banding and the others by conventional Giemsa staining. The karyotypic comparisons arelisted in Table 4. The family Hynobiidae has a wide geographical distribution. Twenty-six species in five genera
out of more than 34 species in eight genera have beenstudied karyologically. The chromosome number varyfrom 40 to 80 . Twelve species in Hynobius and one in
Salamandrella had been studied by C-banding, AgNORs staining, and R-banding. The relationships in thetwo genera were discussed by comparing banded karyotypes and Southern hybridizations. It is suggested thatthe family is the most primitive living caudate(Morescalchi, 1973; Kohno et al., 1991).The same conclusion is derived from morphological comparisons(Zhao and Hu, 1984).
There are 17 species in seven genera in Hynobiidae
known from China. The family can be divided into twogroups: Hynobius group and Ranodon group. The

Ranodon group evolved by adaptation towards two different life-forms: aquatic and terrestrial. Liua andBatrachuperus are aquatic and are closely related. Table
4 shows that seven species have high chromosome numbers: 2n=62-68. Their karyotypes are bimodal and symmetrical, with more microchromosomes (Yang, 1992).
Salamandrella keyserlingii has 2n=62 chromosomes,
the karyotype formula being 4M + 2SM + 10ST + 10T+ 36 m (Wang et al., 1983) in accordance with thatreported by Morescalchi (1975), Morescalchi et al.
(1979), Grafodatsky et al. (1978), Kuro-o(1986), andIkebe et al. (1990). The bivalent number in cells of male
Batrachuperus pinchonii in diakinesis is 31. We expect
the diploid chromosome number to be 2n=62 (Yang andZhao, 1984), but this species also has 2n=66 chromosomes (Kuro-o et al., unpublished data). There is little
detailed information on the cause of the difference.
The karyotypic differentiation of Hynobiidae ismore complex. First, variations in diploid chromosome
number occurred not only at the intergeneric level,but
also at the intrageneric level. For instance,
Salamandrella has 2n=62, Batrachuperus 2n=62-68,
both Liua and Pachyhynobius 2n=64. Secondly, thenumbers of microchromosomes vary from 36 to 46.
Finally, the morphology of microchromosomes are variable. The numbers of M, SM, and ST are species-specific. Telocentric macrochromosomes were found in S. keyserlingii, L. shihi and P. shangchengensis, but not in
Batrachuperus. The L. shihi and P. shangchengensis
studied were from the type localities (Zhao and Hu,
1983; Fei et al., 1983). Both two species have 2n=64
chromosomes, different from the known genera.
However, they are different in morphology ofmacrochromosome and microchromosome number(Table 4) . Therefore, the cytogenetic data provide evidence supporting those genera and species.
There are four species in Batrachuperus.
Batrachuperus karlschmidti and B. yenyuanensis are
only found higher than 3000M in the Hengduan
Mountains, having 2n=68, no telocentric macromosomes and 44 and 46 microchromosomes respectively.
Batrachuperus pinchonii and B. tibetanus distributed
higher than 1600M of Hengduan Mountains and adjacent areas have 2n=62. Obviously, the karyotypic differ-

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Asiatic Herpetological ResearchVol. 10, p. 302

Table 4. Karyological comparisons of urodela in China. M-metacentric macrochromosomes; SM-submetacentric
macrochromosomes; ST-subtelocentric macrochromosomes; T-telocentric macrochromosomes; m-microchromosomes.
SpeciesHynobiidae
Salamandrella keyserlingii
Batrachuperus karlschmidti
B. yenyuanensis
B. pinchonii
B. tibetanus
Liua shihi
Pachyhynobius shangchengensis
Salamandridae
Tylototriton kweichowensis
T. verrucosus
Cynops cyanurus yunnanensis
C. orientalis
Paramesotriton chinensis
Pachytriton brevips
P. labiatum

2N

62
68
68
(62)
62
64
64
24
(24)
(24)
24
(24)
24
(24)

Number of
Bivalent

M

SM

ST

T

m

Band

4
6
4

2
2

10
18
16

10
-

36
44
46

6
4

2
-

4
2

10
18

42
40

--------

16

6

2

-

-

16

8

-

-

-

16

8

-

-

-

31

12
12
12
12
12

entiations in Batrachuperus are in conformity with thegeographic distribution.
Salamandridae is the advanced family in Caudata
either from the viewpoint of karyotypic information orfrom that of morphological characteristics (Morescalchi,
1973, 1975, 1979; Zhao and Hu, 1984; Yang,
1992).There are five genera of Salamandridae found in
China:
Tylototriton,
Echinotriton,
Cynops,Paramesotriton, and Pachytriton. Of the five genera,
Tylototriton is the most primitive and Pachytriton themost advanced . The seven species studied in five genera have the same chromosome number, 2n=24, without
microchromosomes. The karyotypes are unimodal andsymmetrical (Table 3). Interspecific differences were
found in Tylototriton. The karyotypic formula of T. kweichawensis is 16M+6SM+2ST, the same as that of T.
verrucosus. However, Nos. 6, 8 and 11 are submetacentric and no secondary constriction was found in the former (Yang, 1990), while Nos.6, 7 and 11 are submetacentric and secondary constriction were found at every
chromosomes except No.12 in the latter (Seto et al.,1982). Echinotriton andersoni has 2n=24 chromosomes,
14M + 8SM+ 2ST, one more submetacentric chromosome pair than both T. kweichowcensis and T.verrucosus(Seto et al., 1982). In addition, the relative length ofchromosome No. 1 is the longest and that of No.12 theshortest in E. andersoni among the three species mentioned above. The karyotypic formulas of Pachytriton
brevipes and Cynops orientalis are nearly identical andonly the differences of C-band patterns are found (Zhuand Wei, 1981).
The predominant mode of karyotypic evolution in
Caudata is that the unimodal symmetrical karyotypes
with fewer chromosome number are derived from the

---C
-C
--

bimodal and asymmetrical karyotypes with more chromosome number, via Robertsonian centric fusions andpericentric
inversions(Morescalchi,1975).
Robertsonian centric fusions, which could occur
between telocentric macrochromosomes, between stablemicrochromosomes,
andbetweentelocentric
macrochromosomes and stable microchromosomes,
cause reduction of the diploid number and themicrochromosome number and increase of the metacentric chromosomes. Consequently, the karyotypes tend
toward stability. Pericentric inversions do not change thediploid number, but could increase the number of metacentric chromosomes and the stability of karyotypes.
There are some differences in the evolutionary
trends of Hynobiidae and Salamandridae. The karyotypic evolution in Hynobiidae involves Robertsonian centric fusion as well as pericentric inversion. However, thephylogeny of the family could not be established on theavailable data. It is obvious that the karyotypes ofSalamandridae are more stable than those of
Hynobiidae. Morescalchi (1975) proposed that all
species studied possess similar karyotypes that differ
very little even at the intergeneric level. The differences
between the karyotypes mainly lie in the absolute size ofchromosomes and quantity of DNA. Accordingly, thekaryotypic diversity among the species has chiefly
resulted from pericentric inversions and reciprocaltranslocations that result in differences between individual chromosomes by changing the telocentric chromosomes into metacentric ones or changing the metacentricchromosomes into submetacentric, subtelocentric andtelocentric chromosomes.

Vol. 10, p. 303

Asiatic Herpetological Research

Acknowledgments
I want to express my thanks to three professors: Zhao
Ermi, Chen Wenyuan and Wang Xizhong. Under theirencouragement and guidence this paper was worked
out. Sincere thanks are also extended to professor
Zheng Xuejing, who read and made some corrections
to this paper.

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