AmphibiaChina 中国两栖类.

Description
Leptobrachella laui is a small frog that has a snout-vent length range in adult males of 24.8 – 26.7 mm and a single adult female is 28.1 mm. The head is slightly longer than wide, and the snout looks rounded from above but is relatively truncated on the side. The nostrils are closer to the tip of the snout than to the eyes. The canthus ridge is distinct and bluntly rounded. The lores are slightly concave. The eyes are large with vertical pupils. The eardrums are smaller than the eyes, distinct and round, and with a raised rim. Supratympanic folds are present. The finger tips are rounded, without nuptial pads or finger webbing. Relative finger lengths are I < IV < II < III. There is a big, round inner pad and a small, round outer pad on each palm. The toe tips are rounded and webbed at the base. Relative toe lengths are I < II < V < III < IV. Longitudinal ridges under toes II – V are extended on the plantar side of phalanges and do not interrupt at articulations. Subarticular tubercles and outer metatarsal tubercles are absent whereas large oval inner metatarsal tubercles are present. The skin on the back is shagreened with fine, round, and scattered tubercles. Skin on the underside is smooth. The femoral glands on the posteroventral surface of the thigh are oval, with a greatest width of 0.8 mm and a greatest length of 0.9 mm, closer to the knee than to the vent. Axillary glands are 1.0 mm in width and 1.8 mm in length. Ventrolateral glands are present, forming a complete line on the side (Sung et al. 2014).

DIAGNOSIS: (How this species is differentiated from similar species)

Leptobrachella laui differs from congeners by a combination of physical traits. 1) They are medium size. The snout-vent length of adult males is 24.8 – 26.7 mm and of a single adult female is 28.1 mm; 2) The species has a completely creamy-white chest and belly, while other species have a stained underside that varies from brown to dark brownish red; 3) Their fingers have broad lateral fringes but congeners have little or no fringes. For example, L. laui has fringes on both sides of the finger II, III and IV, while L. firthi only has wide dermal fringes on finger II; 4) The head of L. laui is longer than or as long as wide, however, congeners all have heads wider than long; 5) L. laui has distant dark brown spots on the flank, of which L. eos lacks; 6) Compared to L. liui that has a grayish-brown dorsum, L. laui has a brown or reddish brown dorsum; 7) The skin of L. laui is scattered with rounded granular tubercles and without glandular folds, while L. liui has glandular folds; 8) L. laui has thin traverse brownish grey bars on the dorsal surface of tibia and lower arms, versus the wider bars in L. liui; 9) The dorsum of L. laui lacks light markings in preservative, which contrasts with the dorsal large dark markings edged with light margins in L. liui; and 10) The longitudinal ridges under toes of L. laui are not interrupted at the articulations, but the ridges are interrupted in L. liui (Sung et al. 2014).

COLORATION: (In life and/or in preservative)

A live specimen has a brown dorsal surface scattered with tiny buff spots, but no distinct darker markings. Faint transverse brownish grey bars are found on the dorsal surface of its fingers, lower arms, tarsus, thigh and tibia. Fingers, toes and elbow to upper arm are pale copper. The ventral surface of chest and belly is opaque creamy-white with little brown dusting along the margins of ventrolateral glands. The throat is transparent pink with brown dusting along the anterior margin. The ventral surface of its arms and thighs is pink with brown dusting along lateral sides, and the ventral surface of tarsus and tibia is brownish pink with creamy white flecks. The axillary, femoral and ventrolateral glands are pale copper. The iris is uniformly coppery orange with fine black reticulations throughout (Sung et al. 2014).

A preserved specimen has a brown dorsal surface and a creamy-white chest and belly. Brown pigments are found on the belly along the edge of the ventrolateral glands. The underside of all limbs is brown (Sung et al. 2014).

Tadpoles are greyish-brown or dark-brown and about 30 mm long. The tip of their tails is round with a transparent tail fin (Programmes of Ecology and Biodiversity 2021).

VARIATION:

From the observation of 11 specimens, indistinct darker markings similar to the holotype are common with variation of color between individuals. One of the paratypes collected from Hong Kong has a distinctive darker greyish-brown triangle between the eyes, w-shaped dark marking on shoulder region and scattered large greyish-brown flecks over the iliac region (Sung et al. 2014).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: China

View distribution map in BerkeleyMapper.

This species was first recorded in 1979 on Lantau Island, Hong Kong (Karsen et al. 1998). They can be found in New Territories and Outlying Islands of Hong Kong, including Tai Po Kau, Tai Mo Shan, Kadoorie Farm and Botanic Garden, Ho Chung and Shing Mun, and at Sunset Peak and Lantau Peak on Lantau Island (Sung et al. 2014). More recent sightings were made in Ma On Shan Country Park (Hui 2019) and Lion Rock Country Park (Lagwan 2018). They were also recorded in Wutongshan, Shenzhen, Guangdong Province. However, the exact distribution of this species in mainland China is unknown (Sung et al. 2014).

Leptobrachella laui inhabits rocky, mountain streams in forests located at an elevation of 100 – 800 m (Sung et al. 2014). They prefer streams with moderate to complete canopy cover, regardless of stream width (Karsen et al. 1998).

Life History, Abundance, Activity, and Special Behaviors

Leptobrachella laui is strictly nocturnal and feeds on ants, termites and other small insects. Adults burrow and have adhesion discs on their forelimbs to help climbing on steep surfaces in rocky streams which they inhabit.

The breeding season is from February to September in Hong Kong. During this period, males advertise by making high pitched, cricket-like chirps for territorial defense and attracting females [Listen to frog call in the reference] (Agriculture, Fisheries and Conservation Department 2021). Advertising males can be located at the entrance of burrows or on top of boulders, and within two meters from streams (Karsen et al. 1998, Chan et al. 2005). Females exhibit sex-reversed inguinal amplexus by clasping onto the back of a chosen male, which carries the female to a concealed rock crevice for external fertilization and egg deposition (Sung et al. 2021).

As of 2021, L. laui is the only known species in which the females exhibit sex-reversed inguinal amplexus. All other known amplexus involve the male on top of or in line horizontally (cloacal apposition) with the female. It is postulated that limiting suitable oviposition sites or strong competition for males among females could be evolutionary drivers for the development of this behavior (Sung et al. 2021).

Tadpoles are bottom dwellers and complete metamorphosis in approximately 20 days (Programmes of Ecology and Biodiversity 2021).

Predators include snakes and bigger frogs that also inhabit high-altitude mountain streams and are distributed in similar areas, such as the Asiatic Water Snake (Trimerodytes aequifasciatus), Striped Stream Snake (Opisthotropis) and Lesser Spiny Frog (Quasipaa exilispinosa) (Karsen et al. 1998). When disturbed, an adult is able to expand its body and secrete sticky mucus (Chan et al. 2005).

Trends and Threats
Susceptible to habitat loss and destruction and water pollution.

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Urbanization
Predators (natural or introduced)

Comments
Leptobrachella laui in Hong Kong was originally identified as Leptolalax pelodytoides pelodytoides by Pope (1931) because it was morphologically similar to L. pelodytoides found in Fujian Province, China. This species name was applied to other species geographically close to the Fujian population (Ohler et al. 2011). It was later distinguished as a new species, Leptolalax liui, based on data from morphology, osteology, and larval stages (Fei et al. 1990a). In 2014, Leptolalax liui was renamed as L. laui after a molecular study by Sung et al. (2014) based on a 412 bp fragment of the mitochondrial 16S rRNA locus. The team found that specimens collected in Shenzhen and Hong Kong represented the same species, L. laui, which is genetically close but separated from L. liui. Finally, Chen et al. (2018) did a large-scale test that examined multiple nuclear DNA markers of the formerly known Leptolalax species, and Leptolalax laui was assigned to the genus Leptobrachella, hence, the current name Leptobrachella laui.

The genus Leptobrachella is diverse and new species have been frequently described in Asia, up to 86 species (Frost 2021, Wang et al. 2020, Luo et al. 2020, Chen et al. 2019, Wang et al. 2018). There are currently 29 species in China. Phylogenetic studies by Chen et al. (2019) and Luo et al. (2020) yielded similar results from reconstructing a Bayesian tree based on DNA sequences of partial 16S rRNA mitochondrial locus (~530 bp). The results showed that L. laui belongs to the same clade as L. liui, L. mangshanensis, L. maoershanensis and L. yunkaienesis. Another study analyzing 2527 bp sequence of mitochondrial 12S rRNA and 16S rRNA loci inferred that L. laui is the same clade as L. ventripunctatus, L. minimus and L. bourreti (Matsui et al. 2017).

The 29 species of Leptobrachella confirmed in China: L. alpina (Fei, Ye, and Li 1990), L. aspera (Wang, Lyu, Qi, and Wang 2020), L. eos (Ohler et al. 2011), L. feii (Chen, Yuan, and Che 2020), L. flaviglandulosa (Chen, Wang, and Che 2020), L. niveimontis (Chen, Poyarkov, Yuan, and Che 2020), L. pelodytoides (Boulenger 1893), L. purpurus (Yang, Zeng, and Wang 2018), L. tengchongensis (Yang, Wang, Chen, and Rao 2016), L. ventripunctata (Fei, Ye, and Li, 1990) and L. yingjiangensis (Yang, Zeng, and Wang, 2018) from Yunnan; L. bashaensis (Lyu et al. 2020), L. bijie (Wang, Li, Li, Chen, and Wang 2019), L. chishuiensis (Li, Liu, Wei, and Wang 2020), L. dorsospina (Wang, Lyu, Qi, and Wang 2020), L. jinshaensis (Cheng, Shi, Li, Liu, Li, and Wang 2021), L. purpuraventra (Wang, Li, Li, Chen, and Wang 2019) and L. suiyangensis (Luo, Xiao, Gao, and Zhou 2020) from Guizhou; L. yunkaiensis (Wang, Li, Lyu, and Wang 2018) from Guangdong; L. mangshanensis (Hou, Zhang, Hu, Li, Shi, Chen, Mo, and Wang 2018) and L. wulingensis (Qian, Xiao, Cao, Xia, and Yang 2020) from Hunan; L. maoershanensis (Yuan, Sun, Chen, Rowley, and Che 2017), L. shangsiensis (Chen, Liao, Zhou, and Mo 2019), L. sungi (Lathrop, Murphy, Orlov, and Ho 1998) and L. wuhuangmontis (Wang, Yang, Wang 2018) from Guangxi; L. bourreti (Dubois 1983) from Yunnan and Guangxi; L. laui (Sung, Yang, and Wang 2014) from Guangdong and Hong Kong; L. liui (Fei and Ye 1990) from Guizhou, Guangxi, Guangdong, Hunan, Fujian, Jiangxi and Zhejiang; and L. oshanensis (Liu 1950) from Gansu, Sichuan, Chongqing, Guizhou, and Hubei.

ETYMOLOGY

References

Agriculture, Fisheries and Conservation Department. (2021, April 23). “Amphibians of Hong Kong.” https://www.afcd.gov.hk/english/conservation/hkbiodiversity/speciesgroup/speciesgroup_amphibians.html#calls Downloaded in April 2021

Chan S.K.F., Cheung K.S., Ho C.Y., Lam F.N., Tang W.S. (2005). A Field Guide to the Amphibians of Hong Kong. Agriculture, Fisheries and Conservation Department, Friends of the Country Parks and Cosmos Books Ltd., Hong Kong.

Chen, J. M., Poyarkov, N. A., Suwannapoom, C., Lathrop, A., Wu, Y-H, Zhou, W-W, Yuan, Z-Y, Jin, J-Q, Chen, H-M, Liu, H-Q, Nguyen, T. Q., Nguyen, S. N., Duong, T. V., Eto, K., Nishikawa, K., Matsui, M., Orlov, N. L., Stuart, B. L., Brown, R. M., Rowley, J. J. L., Murphy, R. W., Wang, Y-Y, Che, J. (2018). "Large-scale phylogenetic analyses provide insights into unrecognized diversity and historical biogeography of Asian leaf-litter frogs, genus Leptolalax (Anura: Megophryidae)." Molecular Phylogenetics and Evolution 124: 162–171. [link]

Chen, W., Liao, X., Zhou, S., Mo, Y. (2019). "A new species of Leptobrachella (Anura: Megophryidae) from southern Guangxi, China." Zootaxa 4563(1): 67–82. [link]

Frost, D. R. (2021). “Leptobrachella Smith, 1925.” In: Amphibian Species of the World: an Online Reference. Version 6.1. Retrieved April 23, 2021, from https://amphibiansoftheworld.amnh.org/index.php. American Museum of Natural History, New York, USA. doi.org/10.5531/db.vz.0001

Hui, T. (2019, March 27). “Leptobrachella laui”. iNaturalist. https://www.inaturalist.org/observations/21658143 Downloaded in April 2021

Karsen, S.J., Lau, W.-N. M., Bogadek, A. (1998). Hong Kong Amphibians and Reptiles. Provisional Urban Council, China.

Lagwan. (2018, April 30). “Leptobrachella laui”. iNaturalist. https://www.inaturalist.org/observations/11767164 Downloaded in April 2021

Luo, T., Xiao, N., Gao, K., Zhou, J. (2020). "A new species of Leptobrachella (Anura, Megophryidae) from Guizhou Province, China." ZooKeys 923: 115–140. [link]

Matsui, M., Eto, K., Nishikawa, K., Hamidy, A., Belabut, D., Ahmad, N.,Panha, S., Khonsue, W., Grismer, L. (2017). "Mitochondrial phylogeny of Leptolalax from Malay Peninsula and Leptobrachella (Anura, Megophryidae)." Current Herpetology 36(1): 11–21. [link]

Pope, C. H. (1931). ''Notes on amphibians from Fukien, Hainan, and other parts of China.'' Bulletin of the American Museum of Natural History, 61, 397-611.

Programmes of Ecology & Biodiversity (2021, April 23). “Images of Amphibians of Hong Kong”. Programmes of Ecology & Biodiversity, University of Hong Kong, Retrieved. https://www.biosch.hku.hk/ecology/hkamphibians/index.htm Downloaded in April 2021

Sung, Y. H., Lee, W. H., Ng, H. N., Crump, M. L., Karraker, N. E. (2021). "Novel reproductive behavior in an Asian frog: sex‐reversed inguinal amplexus." Ecosphere 12(3):e03407. [link]

Sung, Y. H., Yang, J., Wang, Y. (2014). "A new species of Leptolalax (Anura: Megophryidae) from southern China." Asian Herpetological Research 5(2): 80–90. [link]

Wang, J., Lyu, Z. T., Qi, S., Zeng, Z. C., Zhang, W. X., Lu, L.-S., Wang, Y. Y. (2020). "Two new Leptobrachella species (Anura, Megophryidae) from the Yunnan-Guizhou Plateau, southwestern China." ZooKeys 995: 97–125. [link]

Wang, J., Yang, J., Li, Y., Lyu, Z., Zeng, Z., Liu, Z., Ye, Y., Wang, Y. (2018). "Morphology and molecular genetics reveal two new Leptobrachella species in southern China (Anura, Megophryidae)." ZooKeys, 776, 105-137. [link]

Species Account Citation: AmphibiaWeb 2021 Leptobrachella laui: Lau's Leaf-litter Toad <https://amphibiaweb.org/species/8201> University of California, Berkeley, CA, USA. Accessed Jun 18, 2021.

Citation: AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Jun 2021.

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