Tadpole of the Critically Endangered Sterling’s Toothed Toad (Oreolalax sterlingae)

Abstract

Sterling’s Toothed Toad, Oreolalax sterlingae (Nguyen et al. 2013), was described from near the summit of the highest peak in Vietnam, Mount Fansipan, Lao Cai Province. The species is the only member of the genus in Vietnam and is presently known from a single stream system on Mount Fansipan at about 2800 m elevation. The closest congener occurs more than 200 km away in China (Fei et al. 2010), and the relationship of O. sterlingae within the genus is not known. Because of its extremely small range and profound habitat modifications and pollution at the site, O. sterlingae was recently assessed as Critically Endangered (IUCN SSC 2015).

Full text

Accepted by F. Candioti: 28 Mar. 2017; published: 31 May 2017
579
ZOOTAXA
ISSN 1175-5326 (print edition)
ISSN
1175-5334
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Copyright © 2017 Magnolia Press
Zootaxa 4272 (4): 579
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Correspondence
https://doi.org/10.11646/zootaxa.4272.4.6
http://zoobank.org/urn:lsid:zoobank.org:pub:CA1F30C9-559B-4E76-9D90-EC99AD8949A7
Tadpole of the Critically Endangered Sterling’s Toothed Toad
(Oreolalax sterlingae)
JODI J. L. ROWLEY
1,2,6
, BENJAMIN TAPLEY
3
, NGUYEN THANH CHUNG
4
& RONALD ALTIG
5
1
Australian Museum Research Institute, Australian Museum, 1 William St, Sydney, NSW, 2010, Australia
2
Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney NSW
2052, Australia.
3
Zoological Society of London, Regent's Park, London, United Kingdom, NW1 4RY
4
Hoang Lien Center for Rescue and Conservation of Organism, Sa Pa, Lào Cai, Việt Nam
5
Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762 U.S.A.
6
Corresponding author. E-mail: jodi.rowley@austmus.gov.au
Sterling’s Toothed Toad, Oreolalax sterlingae (Nguyen et al. 2013), was described from near the summit of the highest
peak in Vietnam, Mount Fansipan, Lao Cai Province. The species is the only member of the genus in Vietnam and is
presently known from a single stream system on Mount Fansipan at about 2800 m elevation. The closest congener occurs
more than 200 km away in China (Fei et al. 2010), and the relationship of O. sterlingae within the genus is not known.
Because of its extremely small range and profound habitat modifications and pollution at the site, O. sterlingae was
recently assessed as Critically Endangered (IUCN SSC 2015).
The original description is the only publication pertaining to this species, and the reproductive behavior and life
history of the species are unknown. We present a description of the tadpole based on live specimens that were not
preserved. During surveys in Hoang Lien National Park from 11‒14 September 2015 (~22.315 Nº, 103.766 Eº, ~2800 m
asl), we captured two tadpoles in small pools in the stream at the type locality of O. sterlingae, a steep stream with a
gravel and rock substrate.
TABLE 1. Measurements (mm) of two Oreolalax sterlingae tadpoles from a stream at ~2800 m asl on Mount Fansipan,
the type locality of the species.
We observed fewer than 10 tadpoles at the stream despite surveys along about 200 m of the stream; tadpoles were
observed during both day and night. Garbage left by tourists was obvious throughout the stream (Fig. 1). We
photographed both tadpoles in water in lateral, dorsal and ventral view with a metric scale in view. We photographed the
mouthparts by holding the tadpole out of water briefly. We removed a small amount of tail tissue from one individual for
molecular analysis, and returned the tadpoles to the collection site. Sterile, nitrile gloves were worn at all times, and we
changed gloves between individuals handled. Although we strongly believe in the importance of voucher specimens, we
chose not to take them in this instance because of the conservation status of the species, ongoing threats and the small
Tadpole 1
(Gosner stage 28)
Tadpole 2
(Gosner stage 29)
TL 34.2 35.3
BL 12.8 13.9
IND 2.3 2.5
HBW 6.2 6.4
IOD 3.4 3.2
TW 2.9 2.6
ODW 2.9 2.8
TH 6.7 6.1
TMH 2.8 3.9

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number of tadpoles observed at the only known locality for the species. Salifert test kits were used to measure ammonia,
nitrite, nitrate, alkalinity and phosphate of the water. Samples were taken in the mid-section of the stream at a depth of 10
cm and tests were carried out following the manufacturer’s guidelines. The pH was 7.5 and the NH
3
was < 0.25 ppm, and
NO
2
, NO
3
, PO
4
, and alkalinity all measured at 0.0 ppm. The water temperature was 14.2ºC.
FIGURE 1. (A) Stream at type locality of Oreolalax sterlingae, on Mount Fansipan, where tadpoles were observed (B‒C) Oreolalax
sterlingae tadpoles in situ.
The identity of the tadpoles was confirmed by analysing the tissue collected from one of the two tadpoles (Tadpole
1). Total genomic DNA was extracted with DNeasy tissue extraction kits (Qiagen), and we used the primers 16SAR and
16SBR of Palumbi et al. (1991) to amplify 550 base pairs of the 16S rRNA gene. Standard PC protocols were used and
PCR products were purified with ExoSap-IT (USB Corporation, OH, USA). Purified templates were sequenced directly
by Macrogen (Seoul, Korea). Sequences were validated with Sequencher 4.10 (Gene Codes, Ann Arbor, MI), aligned
with the Clustal option in MEGA-7, and refined by eye. The newly obtained sequence (GenBank accession number
KY459996) was identical to those from an adult Oreolalax sterlingae collected at the same site in 2012 (AMS R177528,
GenBank accession number KR018125). We used ImageJ 1.49 (Schneider et al. 2012) to measure the tadpoles from the
photographs, staging followed the Gosner (1960) table, and tadpole terminology is that of Altig and McDiarmid (1999).
The ovoid body was slightly flattened above with the snout rounded in dorsal and lateral views, the eyes were dorsal,
the vent was dextral with a long tube, the spiracle was sinistral, and the nares were round (Fig. 2). The large anteroventral
oral disc (ODW/HBW 0.44 and 0.59 in Tadpoles 1 and 2) was positioned anteroventrally. The labial tooth row formula

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was 5(2‒5)/5(1‒4) with LTR P-5 about half the length of P-1‒4. The jaw sheaths were coarsely serrated and notably
convex. The low tail fins taper to a rounded tip. In life, the body was black with obvious neuromasts in lines concentrated
around the nares and eyes, and the pale tail fins were mostly clear with a gold stripe along the anterior half of the upper
and lower margins. Tadpoles were Stage 26 (Tadpole 1) and 25 (Tadpole 2).
FIGURE 2. Tadpole of Oreolalax sterlingae (Tadpole 1) in (A) lateral view, (B) dorsal view, (C) ventral view, and (D) view of the
mouthparts.
Tadpoles of Oreolalax sterlingae conform with the Type A: Leptobrachiini type of Li et al. (2011) that correlates
with a lotic, benthic feeding mode. The tadpoles had a similar body form but were smaller than all Chinese species for
which the tadpoles are known, including those at similar stages (Fei et al. 2010). The black color of O. sterlingae
resembles that of O. granulosus (Fei et al. 2010).
The stream was mostly accessible, and we searched about 200 m of the stream for more than 30 person-hours during
the day and night during amphibian surveys in September 2015 and in July 2016. The discovery of so few tadpoles in
2015 and no tadpoles in 2016, despite observing adults at the site, likely means that reproduction is not common or
successful or that the larval period is short in duration. Other species of frogs that breed in this stream are Leptolalax
botsfordi and Megophrys sp. Nothing is known about the length of the larval life span, the oviposition sites, or egg
morphology.
We did not collect tadpole specimens as voucher specimens because of the conservation status of Oreolalax
sterlingae, the apparent rarity of tadpoles and the ongoing threats to the species. Even if certain details are not obtained

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by describing tadpoles from live specimens in the field, this method can certainly be used to verify the identity and
morphology of highly threatened tadpoles.
Acknowledgements
We thank Director Nguyen Quang Vinh and Mr. Luong Van Hao and all the management team at Hoang Lien National
Park for their assistance and collaboration and the Lao Cai People’s Committee for supporting this programme of
research. Our research was conducted under permit numbers 3155/UBND-NC, 249/VQG-TTCH and 1073/TCLN-BTTN
and animal ethics approval from the Zoological Society of London’s ethics committee (project AES47). This work was
supported, in part, by the Mohammed bin Zayed Species Conservation Fund.
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