2008

Asiatic Herpetological Research, Vol. 11

pp.57–61

The Biology and Taxonomic Status of theSunken Ear Frog (Rana tormotus Wu, 1977)
PIPENG LI* AND YUYAN LU
Liaoning Key Laboratory of Biodiversity and Evolution, Shenyang
Normal University, Shenyang 110034, P. R. China.
*Corresponding author E-mail: lipipeng@yahoo.com
Abstract.- The biology and taxonomic status of the sunken ear frog, Rana tormotus Wu, 1977, are reviewed andbriefly discussed. This is a rare species restricted the mountain streams and rivers of Anhui and Zhejiang provinces
in East China, and is characterized by a sunken tympanic membrane that forms an external ear canal, similar to thatseen in birds. The male, which is known to produce ultrasonic sounds when calling, has a more deeply sunken membrane. The karyotype of this frog is 2n = 26, having five pairs of large, eight pairs of small and seven pairs of submetacentric chromosomes. The frog is active during the night and females are uncommonly encountered. Specimens
are often found in the same habitat as Megophrys boettgeri, Bufo gargarizans, Rana limnocharis, R. schmackeri, Paa
spinosa, Amolops wuyiensis and A. ricketti. This frog was first described within Rana, but it was recombined in
Amolops because its tadpole was of the “Amolops type”, even though the tadpole was unknown at the time. The
recently-discovered tadpole has no abdominal sucker and the poison glands, smaller than and similar to those of R.
schmackeri with LTRF (I:4-4/III:1-1), making it distinct from the “Amolops-type” tadpole. Adult and larval morphology, as well as developmental characters, support the placement of this species in Wurana, a new genus setup recently.
Keywords.- Amphibia, Ranidae, Rana, tormotus, Wurana, Amolops.

Introduction
Rana tormotus Wu, 1977 is a characteristic frog with asunken ear membrane that is particularly distinct in themale, giving this species the common name of “sunken
eared frog” or “concave-eared torrent Frog,” the formerof which translates to “Ao Er Wa” or “Wa Er Wa ” inChinese. In 1972 and 1974, Ermi Zhao, Guanfu Wu andtwo assistants collected one female and 18 male frogs
with sunken tympana at Taohua Creek on Mt. Huanshan.
These frogs were subsequently described as members of
the new species Rana tormotus (Sichuan Institute ofBiology [Wu, G. F.]). During the next 23 years, only afew reports on this frog’s taxonomy and karyotype werepublished (Chen, 1991; Fei et al., 1991; Guo and Dong,1986; Huang et al., 1990). The species was subsequently
moved to Amolops by Fei et al. (1991), because its tadpole might be of the “Amolops type”, even though thetadpole was unknown at the time. The correct taxonomic
placement of this species is currently ambiguous (GlobalAmphibian Assessment, 2005; Zhao and Adler, 1993;
Zhao and Zhao, 1994; Zhao et al., 2000;).
Recently, the ecology, bioacoustics and evolutionary history of this species have been explored by Liu andHua (2001), Wu and Wu (2002) and Feng et al. (2002,2006). We have also completed surveys on its distribution and habitat (at Jiande, Zhejiang and its type locality
at Huanshan, Anhui), which are presented below. We© 2008 by Asiatic Herpetological Research

further placed this species in the new genus Wurana on
the basis of developmental characters and adult and larval morphology (Li et al., 2006).
Distribution and habitat.- This sunken ear frog is a rareendemic species restricted to the mountain streams andrivers of East China at elevations between 150 and 750
m. It is currently known only from the type locality(Taohua Creek, Hotspring Creek, Fu Creek and Xiang
Creek of Huanshan, Anhui Province) and two locations
in Zhejiang province (Huang, et al, 1990, personal communication with Prof. Qinghui Gu): two small creeks inthe Jiangde Forestry Centre and the creeks of Anji
County. The latter creeks are filled with large rocks andare surrounded by trees, brushes and grass (Figs. 1–3).
All frogs were collected at night since they could
not be found during the day. Adult males were found on
rocks in the river and in the surrounding trees andshrubs, and were located by their calls. No females wereobserved; in Liu and Hua (2001), it was reported thatfemales were collected only after midnight following theappearance of males. It was suggested that the females
were not commonly found because they occupied higher
tree branches (Wu and Wu, 2002). Neither sex wasobserved following the breeding season.
Wu and Wu (2002) reported that the frogs were only
found in shrubs along the flat parts of the river. In comparison, at the bases of mountains we found that trees

58

Asiatic Herpetological Research, Vol. 112008

Figure 2. Type locality of Rana tormotus, Taohua Creekof Mt. Huanshan in Anhui province, China.

surrounding areas included Rana nigromaculata,
Microhyla heymonsi, R. livida and R. japonica (Wu andWu, 2002). Tadpoles of Rana schmackeri, Paa spinosa
and Amolops wuyiensi were also collected from Taohua
Creek.
Figure 1. Distribution of Rana tormotus (red square) in
Anhui and Zhejiang province.

were preferentially chosen (57.32% at Taohua Creek and51.9% at Fu Creek), followed by shrubs (31.71% and40.51%) and then rocks in the water (10.98% and7.95%). Liu and Hua (2001) observed 11 of 53 frogs onbranches, four on sand near vegetation along the riverbank and the remainder on exposed sand and rock in theriver far from any vegetation. In the present study at
Taohua Creek, 20% of frogs were found on tree branches, 40% on shrubs, 20% on grass leaves and 20% onrocks; specimens were never found along sandy riverbanks, where they may have been excluded by Ranaspecies. The differences in observations between surveys may be due to climatic variation.
Males were kept in an aquatic box simulating thenatural environment. During the day, the frogs hid in
gaps between stones and vegetation, but at night they
emerged on the surrounding leaves and rocks despite
variation in weather (including rain).
The other frogs found in the same habitat as Rana
tormotus at the type locality were Megophrys boettgeri,
Bufo gargarizans, Rana limnocharis, Rana schmackeri(Boettger, 1892), Paa spinosa (David, 1875) andAmolops wuyiensis (Liu and Hu, 1975) (Liu and Hua,2001; Li, Lu and Lü, 2006). Amolops ricketti was foundinstead of A. wuyiensis at Jiande. Frogs observed in theKaryotype and Ag-banding pattern.- Guo and Dong
(1986) reported the karyotype and Ag-banding pattern ofRana tormotus. The karyotype is 2n = 26, consisting offive pairs of large and eight pairs of small chromosomes.
A secondary constriction is present near the centromere
on the long arms of chromosome 6 and 10. No heteromorphic chromosomes were present. One homologous
pair of NORs were found in the secondary constrictionof chromosome 10 using Ag-AS staining techniques.
There were also seven pairs of submetacentric chromosomes, the largest among frogs with a 2n = 26 karyotype
in the Raninae (Guo and Dong, 1986; Pan et al., 2002).
Calling and related morphological characters.Recently, Feng et al. (2002, 2006) detailed the extraordinarily rich vocal repertoire of the sunken ear frog. Thesefrogs produce countless vocalizations, some of whichshare features of bird songs or primate calls – e.g., ultrasonic frequency, multiple upward and downward FM
sweeps and sudden the onset and offset of selective harmonic components within a call note. Most frog calls goeither up or down, and no others are known to extend
into the ultrasonic range. Frame-by-frame video analysisof the frog's calling behavior suggests the presence oftwo pairs of vocal sacs that may contribute to its remarkable call-note complexity. Electrophysiological studiesof the frog’s auditory midbrain confirmed that its audible range extends into the ultrasonic (Xu et al., 2005).
This characteristic can likely be explained by the fact

2008

Asiatic Herpetological Research, Vol. 1159

Figure 3. Another locality of Rana tormotus at Jiande
county of Zhejiang province, China.

that the frog lives by noisy streams that produce acoustic
signals with significant ultrasonic harmonics that would
mask normal calls; selective pressure on this species
could eventually produce a call that would not bemasked by the wideband noise produced by the river(Peter et al., 2003).
With regard to sound reception, the sunken ear frog
has a unique structural autapomorphy not seen in other
Anura – a sunken tympanic membrane that forms anexternal ear canal like that seen in birds. The tympanic
membrane is more deeply sunken in the male, suggesting that it receives the airborne sound in a manner somewhat different from that in the female (Feng et al., 2006;
Xu et al., 2005).
Tadpoles and taxonomic status.- Several different
species of tadpoles from the frog’s type locality werereared to metamorphosis in the lab. The first morphotype was identified as Amolops wuyiensis, which had an
abdominal sucker and poison glands; the second tofourth morphotypes were without either of these structures. Among latter, one identified as Paa spinosa had arelatively larger body and body-tail length, and frogletsthat very closely resembled the adult in general morphology. The remaining two morphotypes were significantly smaller and had the same LTRF (I:4-4/III:1-1); ofthese, one was externally similar to the adult of Ranaschmackeri and one was similar to the adult of R. tormotus (Fig. 4); the characters used to aid in the separationof these two species were those listed in Li et al. (2006)
and another paper discussing this species in the present
journal issue (Li et al., 2007).
These characters are enough to verify that Rana
tormotus does not have an Amolops-type larva, andFigure 4. Tadpole, froglets and adult male of Rana tormotus (Wu, 1977). (A) Adult male and froglets, (B) tadpoles,(C) froglet just after metamorphosis, (D) froglet in ventral
view.

should be placed elsewhere. This conclusion was verified by examining and comparing the skeletons of Rana
tormotus to the ranine genera Amolops, Pseudoamolops,Rana and Staurior (Li et al., 2006).
Li et al. (2006) designated Rana tormotus as thetype species of the new monotypic genus Wurana (etymologically, the specific epithet honors Wu Guanfu forthe research on this and other frogs), which is known
from Anhui and Zhejiang Provinces, China. Wurana isdiagnosed as follows:
ADULT.- Dorsolateral folds relatively thick andwide; tympanum deep, forming an external auditory canal that is pronounced in the male; no temporalfolds; male without humeral glands; tarsal folds
absent; tips of fingers and toes expanded into small
disks with circummarginal grooves on outer threedigits; width of crossbar on terminal phalanx muchless than 0.3 times phalanx length.
LARVA.- Small type tadpole with weak horny beak;two rows of lower labial papillae with bases originating in same line; oral disc emarginate laterally,
with single row of truncate marginal papillae inposterolateral margin of upper lip and with wide
rostral gap; labial tooth row formula (LTRF) usual-60

Asiatic Herpetological Research, Vol. 11

2008

ly I:4-4/III:1-1 (sometimes I:3-3/III:1-1); without
external gland groups; spiraculum on the left withfree tube.

Frost, D. 2006. Amphibian Species of the World 3.0, anonline reference. http://research.amnh.org/herpetology/amphibia/index.php.

From the general external morphological and skeletal characters, Wurana is closer to Rana, especially tosome of the odorous frogs, than Amolops.
The surveys done by Qinghui Gu, Pipeng Li andothers have shown that Wurana tormota is likely either
a threatened or “rapidly declining” species (Global
Amphibian Assessment, 2005; Liu and Hua, 2001). It
has a restricted distribution in a region that is heavilyimpacted by human activities such as sight-seeing,
therefore continued biological research and regional
conservation are strongly recommended.

Global Amphibian Assessment. 2005. Global
Amphibian Assessment - Amolops tormotus. an
onlinereference.
http://www.globalamphibians.org/servlet/GAA?sea
rchName=Amolops+tormotus.

Acknowledgments
This study was supported by Natural Science
Foundation of China (grant no. 30470206 to Pipeng Li).
We thank Prof. Ermi Zhao, Qinghui Gu, Guangfu Wu,Hui Zhao, Xisheng Tang, Song Huang and Shunqing Lϋ
for their help in field surveys and research.

Literature Cited
Chen, B. H. 1992. The Amphibian and Reptilian Faunaof Anhui. Anhui Publishing House of Science andTechnology, Heifei, China.
Dubois, A. 2005. Amphibia Mundi 1. Alytes 23(1–2):
1–24.
Feng, A. S, P. M. Narins and C.H. Xu. 2002. Vocal acrobatics in a Chinese frog, Amolops tormotus.
Naturwissenschaften 89: 352–356.
Feng, A. S, P. N. Narins, C. H. Xu, W. Y. Lin, Z. L. Yu,Q. Qiu, Z. M. Xu and J. X. Shen. 2006. Ultrasoniccommunication in frog. Nature 440: 333–336.
Fei L, C. Y. Ye and Y. Z. Huang. 1991. Key to Chinese
Amphibia. Chongqing Branch, Science andTechnology Literature Publishing House,Chongqing, China. Pp 124–126.
Fei, L, C. Y. Ye, J. P. Jiang, F. Xie and Y. Z. Huang.
2005. An illustrated key to Chinese amphibians.
Sichuan Publishing Group - Sichuan Publishing
House of Science and Technology, Chengdu,China. Pp 150–158.

Guo, C. W. and Y. W. Dong. 1986. Studies on the karyotype and Ag-banding pattern of Rana tormotus
Wu. Acta Herpetologica Sinica 5: 181–184.
Huang, M. H, Y. L. Jin and C. M. Cai. 1990. Fauna
Zhejiang: Amphibia/Reptilia. Zhejiang Science andTechnology Publishing House, Hangzhou, China.
Pp. 77–78.
Li, P. P., Y. Y. Lu, A. Li and F. L. Yu. 2008. Tadpole of alittle-known frog, Wurana tormotus. Asiatic
Herpetological Research, 11:71–75.
Li, P. P, Y. Y. Lu and S. Q. Lϋ. 2006. Taxonomic statusof Rana tormotus Wu, 1977 with description of a
new genus of subfamily Raninae. Sichuan Journalof Zoology, 25(2): 206–209.
Liu, B. R. and T. M. Hua. 2001. Ecological research ofRana tormotus. Journal of Biology 18(3): 27–28.
Pang, Q. P., Y. Ye. and Y. T. Wen. 2003. Chromosome
data of Chinese amphibians. Chinese Journal ofZoology 37(4): 49–62.
Peter, M. N, A. S. Feng and W. Y. Lin. 2004. Old Worldfrog and bird vocalizations contain prominent ultrasonic harmonics. J. Acoust. Soc. Am. 115(2):910–913.
Sichuan Institute of Biology (Wu, G. F.). 1977. A newspecies of frogs from Huang-Shan, Anhui - Ranatormotus Wu. Acta Zoologica Sinica 23(1):
113–115.
Wu, H. L. and X. B. Wu. 2002. Habitat selection andfood habit of Rana tormotus. Herpetologica Sinica
9: 123-126.
Yu, Z. L, Q. Qiu, Z. M. Xu, J. X. Shen, A. Feng, P.
Narins and W. Y. Lin. 2005. A study of sound communication and hearing in the concave-eared torrent frog (Amolops tormotus). Herpetologica Sinica
10:266–268.

2008

Asiatic Herpetological Research, Vol. 1161

Zhao, E. M. and K. Adler. 1993. Herpetology of China.
Published by Society for the Study of Amphibians
and Reptiles in cooperated with Chinese Society forStudy of Amphibians and Reptiles. Oxford, Ohio,USA.
Zhao, E. M, H. W. Chang and X. L. Zhao. 2000.
Taxonimic bibliography of Chinese amphibia andreptilian, including karyological literature.
Herpetological Series 11: 215–238. Kaohsiung FuWen Publishing Co. Ltd, Taiwan, China.
Zhao, E. M. and H. Zhao. 1994. Chinese Herpetological
Literature - Catalogue and Indices. Chengdu
Science and Technology University Press,Chengdu, China.

Submitted: 16 October 2006
Accepted: 25 November 2007