Leptobrachella dong, Liu & Shi & Li & Zhang & Xiang & Wei & Wang, 2023

Liu, Jing, Shi, Shengchao, Li, Shize, Zhang, Mengfei, Xiang, Sunjun, Wei, Gang & Wang, Bin, 2023, A new Asian leaf litter toad of the genus Leptobrachella (Amphibia, Anura, Megophryidae) from central south China, ZooKeys 1149, pp. 103-134 : 103

Leptobrachella dong sp. nov.

Figs 3 , 4 , 5

Type materials.

Holotype. CIB SSC1757, adult male (Figs 3 , 4 ), collected by Shengchao Shi in Tongdao County (26.206674°N, 109.952695°E, ca. 790 m a.s.l.), Hunan Province, China on 2 April 2017.

Paratypes. Four adult males CIB SSC1754, CIB SSC1758, CIB SSC1759, CIB SSC1760, one adult female CIB SSC1755 and one tadpole CIB WB2020277 from the same place as holotype collected by Sheng-Chao Shi. Two adult males CIB LB20220305001 and CIB LB20220305003 and five adult females CIB LB20220306003, CIB LB20220306005, CIB LB20220305010, CIB LB20220306008 and CIB LB20220306009 collected by Shize Li from Congjiang County (25.572492°N, 108.274189°E, 1200 m a.s.l.), Guizhou Province, China on 6 March 2022. Two adult males CIB LB20220311001 and CIB LB20220311002 collected by Jing Liu from the same place as Congjiang County, Guizhou Province, China on 11 March 2022; One adult female CIB ZNY2022003 and two adult males CIB ZNY2022001 and CIB ZNY2022002 collected by Fu Shu and four adult males CIB ZNY2022010, CIB ZNY2022011, CIB ZNY2022012 and CIB ZNY2022013 collected by Keji Guo from the same place as Suining County (26.401561°N, 110.093467°E, 620 m a.s.l.), Hunan Province, China on 15 March 2022.

Diagnosis.

Leptobrachella dong sp. nov. is assigned to the genus Leptobrachella , based on molecular data and the following morphological characters: medium size, rounded finger tips, the presence of an elevated inner palmar tubercle not continuous to the thumb, presence of macroglands on body (including supra-axillary, pectoral and femoral glands), vomerine teeth absent, tubercles on eyelids and anterior tip of snout with vertical white bar ( Dubois 1983; Fei et al. 2009).

Leptobrachella dong sp. nov. could be distinguished from its congeners by a combination of the following characters: (1) body of medium size (SVL 29.2-32.0 mm in 15 adult males and 37.4-43.1 mm in seven adult females); (2) distinct black spots present on flanks; toes rudimentary webbed, with wide lateral fringes; (3) ventral belly white with distinct nebulous brown speckling on ventrolateral flanks; (4) skin on dorsum shagreened with fine tiny granules or short ridges; (5) heels overlapped when thighs are positioned at right angles to the body; (6) tibia-tarsal articulation reaches the middle eye; (7) dorsal surface of tadpole semi-transparent light brown, spots on tail absent, keratodont row formula I: 3+3/2+2: I; (8) calls with two types, at dominant frequency (5.1 ± 0.4 kHz).

Description of holotype.

Adult male. SVL in 32.0 mm. Head width almost equal with head length slightly (HDW / HDL 1.03); snout rounded in both ventral view and lateral view, projecting slightly beyond margin of the lower jaw; nostril closer to snout than eye; loreal region oblique; canthus rostralis indistinct; eyes large (ED / HDL 0.40), eye diameter slightly longer than snout length (ED / SL 1.07), eyes notably protuberant in both dorsal and lateral views, pupil vertical; tympanum distinct, rounded, tympanum diameter smaller than eye (TYD / ED 0.38), upper margin of tympanum in contact with supratympanic ridge; vomerine teeth absent; tongue notched behind; supratympanic ridge distinct, extending from posterior corner of eye to supra-axillary gland.

Fore-limb relatively long (LAL / SVL 0.46), fingers long and slender (ML / SVL 0.25), webbing absent, lateral fringes on fingers narrow; relative finger lengths II <I <IV <III; tips of fingers rounded and slightly swollen; subarticular tubercles absent on fingers, inner metacarpal tubercle large and rounded, separated from the smaller, round outer metacarpal; supra-axillary glands oval.

Hind-limb relatively long (HLL / SVL 1.53), heels overlapping when the tibias perpendicular to the body axis; tibio-tarsal articulation of adpressed limb reaching middle of eye, tibia length about half of snout-vent length (TL / SVL 0.49); relative toe length: I <II <V <III <IV; toe tips rounded and slightly swollen; rudimentary webbing present between all five toes; wide lateral fringes present on all toes; dermal ridges under fourth toes interrupted; subarticular tubercles distinct under the base of II, III and IV toe; inner metatarsal tubercle oval and distinct, outer metatarsal tubercle absent (Fig. 3C ).

Dorsal skin relatively smooth with small tubercles and short folds; supra-axillary gland distinct and yellowish; pectoral gland small and indistinct; round femoral glands present and protuberant on rear of thigh, closer to knee than to vent; femoral adipose glands distinct, attached to inner side of skin on posterior ventral surface of thigh; ventral skin smooth; ventrolateral glands forming a distinct white line on flanks.

Colouration of holotype in life.

In life, dorsal surface of head and trunk yellowish-brown, with distinct olive reverse-triangle dark markings between eyes connecting to a dark W-shaped marking between axillae that are fringed with greyish-white colour; elbow to upper arm distinctly yellowish-orange in colour on the dorsum; four transverse black bars present on dorsal surface of thighs and three on dorsal surface of lower arm; one dark blotch between nostril and eyes on loreal region and a dark blotch under the eye; supratympanic ridge reddish and a large black marking under supratympanic ridge; distinct dark blotches on flanks from groin to axilla, longitudinally in two rows; ventral surfaces light coloured; throat and ventral arms pinkish with cream speckling on margins; chest and belly cream white, on the lateral belly with dense brown speckling; ventral hind-limbs pinkish with sparse white glands; upper iris copper, lower iris silver.

Preserved holotype colouration.

Dorsum of body and limbs fading to brown copper; transverse bars on limbs becoming more distinct. Ventral surface of body and limbs fading to cream white. Supra-axillary, femoral and pectoral glands fading to cream yellow.

Variations.

Measurements and basic statistics of adult specimens are presented in Suppl. materials 1, 3, respectively. Females larger than males (29.2-34.2 mm in 15 adult males and 34.4-43.1 mm in seven adult females) and, in CIB LB20220311002, dark blotch between nostril and eyes on loreal region absent (Fig. 5A ); in CIBSCC1754, a patch on the outside of the reverse-triangle dark markings between eyes (Fig. 5B ); in CIB LB20220305005, no longitudinal stripes along dorsolateral body (Fig. 5C ); in CIB LB20220306008, the colouration of head and anterior dorsum is darker than the posterior (Fig. 5D ).

Bioacoustics.

(Fig. 6 ; Suppl. material 3). Calls recorded at temperatures 11.2 to 15.0 °C. Descriptions based on six sequenced adults (Suppl. material 3) and 157 calls were measured. Dominant frequency of all type of calls is 4.4-5.6 kHz (5.1 ± 0.4) kHz, call duration is 203.783 ± 161.7 ms, call interval is 1238.3 ± 2034.5 ms, call repetition rate is 1.61 ± 0.9 (calls/s). Additionally, the calls were of two types. The first type (type A) consists of repeated short notes (Fig. 6A, B ), and the second type (type B) consists of two repeated short notes and with longer call duration (524.2 ± 64.2 ms) and shorter call interval (148.8 ± 72.8 ms) than type A (Fig. 6C, D ). Amplitude of type A was largest at first pulse, drastic reducing in the following pulses; amplitude of second note of type A about half of the first note; amplitude of type B with highest pulse at the beginning of each note and decreasing towards to the end.

Comparisons.

Compared with the 26 known congeners occurring south of the Isthmus of Kra, Leptobrachella dong sp. nov. could be distinguished from them by several characters: by having supra-axillary and ventrolateral glands, the new species differs from L. arayai , L. dringi , L. fritinniens , L. gracilis , L. hamidi , L. heteropus , L. kajangensis , L. kecil , L. marmorata , L. maura , L. melanoleuca , L. picta , L. platycephala , L. sabahmontana , and L. sola (vs. absent in the latter); by having rounded fingertips and moderate body size (29.2-34.2 mm in 15 adult males and 34.4-43.1 mm in seven adult females), the new species differs from the following species with pointed fingertips and smaller body size: L. baluensis (14.9-15.9 mm in males), L. bondangensis (17.8 mm in male), L. brevicrus (17.1-17.8 mm in males), L. fusca (16.3 mm in male), L. itiokai (15.2-16.7 mm in males), L. juliandringi (17.0-17.2 mm in males), L. mjobergi (15.7-19.0 mm in males), L. natunae (17.6 mm in one adult male), L. palmata (14.4-16.8 mm in males), L. parva (15.0-16.9 mm in males) and L. serasanae (16.9 mm in female).

Leptobrachella dong sp. nov. could also be identified from 65 known Leptobrachella species occurring north of the Isthmus of Kra by some characters (see Table 4 ).

By having medium size of body (SVL 29.2-34.2 mm in males) Leptobrachella dong sp. nov. differs from the smaller males L. aerea (25.1-28.9 mm), L. alpina (24.0-26.4 mm), L. applebyi (19.6-22.3 mm), L. ardens (21.3-24.7 mm), L. aspera (22.4 mm), L. bashaensis (22.9-25.6 mm), L. bidoupensis (23.6-24.6), L. crocea (22.2-27.3 mm), L. feii (21.5-22.8 mm), L. flaviglandulosa (23.0-27.0 mm), L. isos (23.7-27.9 mm), L. graminicola (23.1-24.6 mm), L. khasiorum (24.5-27.3 mm), L. lateralis (26.9-28.3 mm), L. laui (24.8-26.7 mm), L. liui (24.8-26.7 mm), L. maculosa (24.2-26.6 mm), L. mangshanensis (22.22-27.76 mm), L. maura (26.1 mm), L. melica (19.5-22.8 mm), L. murphyi (23.2-24.9 mm), L. niveimontis (22.5-23.6 mm), L. pallida (24.5-27.7 mm), L. petrops (23.6-27.6 mm), L. pluvialis (21.3-22.3 mm), L. puhoatensis (24.2-28.1 mm), L. pyrrhops (25.0-27.5 mm), L. rowleyae (23.4-25.4 mm), L. tadungensis (23.3-28.2 mm), L. tengchongensis (23.9-26.0 mm), L. ventripunctata (23.7-27.7 mm) and L. yingjiangensis (25.7-27.6 mm) and differs from the larger in males L. nahangensis (40.8 mm), L. platycephala (35.1 mm), L. sungi (48.3-52.7 mm in males) and L. zhangyapingi (45.8-52.5 mm).

By having a larger size of body (SVL 34.4-43.1 mm in females), Leptobrachella dong sp. nov. differs from the smaller females L. alpina (31.7-32.5 mm), L. applebyi (21.7 mm), L. ardens (25.4 mm), L. aspera (25.0-26.4 mm), L. bashaensis (27.1), L. botsfordi (30.0-31.8 mm), L. graminicola (28.6-32.9 mm), L. isos (28.6-31.5 mm), L. kalonensis (28.9-30.6 mm), L. khasiorum (31.2-33.4 mm), L. liui (24.5-27.8 mm), L. macrops (30.3 mm), L. maculosa (27 mm), L. mangshanensis (30.2 mm), L. maoershanensis (29.1 mm), L. murphyi (29.3-32.1 mm), L. macrops (30.3 mm), L. maoershanensis (29.1 mm), L. niveimontis (28.5-28.7 mm), L. oshanensis (31.6 mm), L. pluvialis (25.5-33.5 mm), L. puhoatensis (27.3-31.5 mm), L. rowleyae (27.0-27.8 mm), L. shimentaina (30.1-30.7 mm), L. suiyangensis (30.5-33.5 mm), L. tadungensis (32.1 mm), L. tamdil (32.3 mm), L. tengchongensis (28.8-28.9 mm) and L. tuberosa (30.2 mm).

By having black spots on flanks, Leptobrachella dong sp. nov. differs from L. aerea , L. botsfordi , L. crocea , L. eos , L. firthi , L. isos , L. pallida , L. petrops , L. tuberosa and L. zhangyapingi (vs. lacking distinct black spots on the flanks in the latter).

By having rudimentary webbing, Leptobrachella dong sp. nov. differs from L. ardens , L. jinshaensis , L. kalonensis , L. maculosa , L. oshanensis , L. pallida , L. petrops , L. rowleyae , L. shiwandashanensis and L. tadungensis (vs. absent webbing in the latter).

By having wide fringes on toes, Leptobrachella dong sp. nov. differs from L. applebyi , L. ardens , L. aspera , L. bashaensis , L. bidoupensis , L. bijie , L. botsfordi , L. bourreti , L. chishuiensis , L. crocea , L. damingshanensis , L. dorsospina , L. feii , L. flaviglandulosa , L. fuliginosa , L. jinshaensis , L. kalonensis , L. lateralis , L. macrops , L. maculosa , L. mangshanensis , L. melica , L. minima , L. nahangensis , L. namdongensis , L. niveimontis , L. nyx , L. oshanensis , L. pallida , L. pelodytoides , L. petrops , L. pluvialis , L. puhoatensis , L. purpuraventra , L. pyrrhops , L. rowleyae , L. shangsiensis , L. shiwandashanensis , L. sungi , L. tengchongensis , L. tuberosa , L. ventripunctata , L. verrucosa , L. wuhuangmontis , L. wulingensis , L. yeae and L. yunyangensis (vs. fringes on toes narrow or absent in the latter).

By having dorsal surface shagreened with fine tubercles, Leptobrachella dong sp. nov. differs from L. applebyi , L. bidoupensis , L. kalonensis , L. melica , L. minima , L. nahangensis , L. pingbianensis , L. shangsiensis and L. tadungensis , all of which have the dorsum smooth and L. bourreti (dorsum smooth with small warts), L. fuliginosa (dorsum smooth with fine tubercles), L. liui (dorsum with round tubercles), L. macrops (dorsum roughly granular with large tubercles), L. maoershanensis (dorsum shagreened with tubercles), L. minima (dorsum smooth), L. neangi (dorsum with small, irregular bumps and ridges), L. nyx (dorsum with round tubercles), L. nokrekensis (dorsum tubercles and longitudinal folds), L. pelodytoides (dorsum with small, smooth warts), L. tamdil (dorsum weakly tuberculate, with low, oval tubercles), L. tuberosa (dorsum highly tuberculate), L. yunkaiensis (dorsum with raised warts) and L. wuhuangmontis (dorsum rough with conical tubercles).

The advertisement calls of Leptobrachella dong sp. nov. (Results and Fig. 3 ) differs from all other congeners occurring north of the Isthmus of Kra for which comparable acoustic data are available consisting of uniform and continuous calls with four to five pulses in each note. Of the congeners in the region with known calls, the new species can be separated from L. purpurus , L. tuberosus , L. puhoatensis and L. yingjiangensis by not having an invariably single-note call with irregular intervals. In addition, the dominant frequency of 4.4-5.6 kHz (at 11.2-15 °C) further distinguishes the call of Leptobrachella dong sp. nov. from that of the higher frequency calls of L. aereus (6.2-7.9 kHz at 22.4-25.7 °C), L. yingjiangensis (5.7-5.9 kHz at 19 °C), L. isos (5.9-6.2 kHz at 22.4-22.8 °C) and L. ventripunctatus (6.1-6.4 kHz at 15 °C) and the lower frequency calls of L. applebyi (4.0-4.3 kHz at 21.5 °C), L. ardens (3.1-3.4 kHz at 21.4-24.7 °C), L. bidoupensis (1.9-3.8 kHz at 19-21 °C), L. botsfordi (2.6-3.2 kHz at 14 °C), L. croceus (2.6-3.0 kHz at 21.6-25.1 °C), L. fuliginosus (2.1-2.8 kHz at 19.3-19.6 °C), L. kalonensis (2.8 kHz at 26.4 °C), L. maculosus (2.7-2.8 kHz at 23.3-24.1 °C), L. melicus (2.6-4.0 kHz at 26.1-26.2 °C), L. pallidus (2.4-2.7 kHz at 14.0-21.4 °C), L. pyrrhops (1.91-2.2 kHz at 25 °C), L. rowleyae (3.3-3.5 kHz at 21.5 °C), L. tadungensis (2.6-3.1 kHz at 12.9-22.3 °C) and L. tuberosus (2.6-2.8 kHz at 22.5-24.5 °C).

In mitochondrial DNA trees, Leptobrachella dong sp. nov. was clustered as an independent clade and sister to a clade comprising of L. graminicola and L. yeae . The new species differs from L. graminicola by the following characters: body size larger with SVL 29.2-34.2 mm in adult males and 34.4-43.1 mm in adult females (vs. 23.1-24.6 mm in adult males and 28.6-32.9 mm in adult females); black spots on flanks present (vs. absent); ventral surface white with distinct nebulous brown speckling on ventrolateral flanks (vs. white with brown spots); dorsal surface shagreened with fine tubercles (vs. smooth, with many tubercles); and tibiotarsal articulation reaching to middle of eye (vs. anterior edge of eye). The new species differs from L. yeae by having wide fringes on toes (vs. narrow); dorsal surface shagreened with fine tubercles (vs. relatively smooth with fine tiny granules or short ridges); and males with a pair of subgular internal vocal sacs (vs. internal single subgular vocal sac).

Tadpoles

(in mm). Description based on sequenced tadpole CIB WB2020277 at Gosner stage 27 (Fig. 7 ). Body elliptical elongate in dorsal view; slightly depressed (BH / BW 1.5, BH 4.7, BL 14.7); eyes lateral (ED 0.9), nostril near to snout than eye (NE 2.9, RN 1.6, IND 2.4, SN 3.5); spiracle on left side of body (SS 7.8); keratodont formula I: 3+3/2+2: I; oral disc is cup-shaped with labial papillae (ODW 3.4); TOL 65.8 mm; tail fusiform, approximately 2.5 times as long as snout-vent length, tail height 18.2% of tail length (TH 6.4, TMH 4.6, TMW 3.8); dorsal fin low, arising behind the origin of the tail (SU 20.1); maximum tail depth near mid-length of tail and larger than body depth (TH / BL 1.4, UF 2.1, LF 1.3); the tip of tail rounded and without spots on dorsal of body.

Secondary sexual characteristics.

Adult males with a pair of subgular vocal sacs (Fig. 8B ), femoral adipose glands present on posterior surface of thigh and tiny transparent spines on chest during breeding season. Nuptial pads and spines absent on males.

Ecology notes.

Leptobrachella dong sp. nov. has been found in three localities: Tongdao County and Suining County, Hunan Province and Congjiang County, Guizhou Province, China. Elevations recorded range from 620 m to 1200 m. Population from the Tongdao County inhabited a torrent stream covered by evergreen shrubs and the new species always found on the stones (Fig. 8A, B ). Population from Congjiang County inhabited slow-flowing streams surrounded by evergreen broadleaf forest (Fig. 8C ). Populations from Suining County, Hunan Province inhabited broad mountain stream surrounded by evergreen broadleaf forest (Fig. 8D ). Tadpoles could be found at daytime and night. Gravid females were found by the streams in the type locality (2 April 2017) and Suining County (15 March 2022).

Etymology.

This specific name “dong” refers to the Dong people, as the new species distributed in the concentrated area of Dong people. We suggest its English common name "Dong leaf litter toads" and Chinese name "Dong Zhang Tu Chan ( 侗掌突蟾)”.

Figures

Figure 3. The holotype specimen CIB SSC 1757 of Leptobrachella dong sp. nov. A dorsal view B ventral view C ventral view of hand D ventral view of foot.

Figure 4. Photos of the holotype CIB SSC 1757 of Leptobrachella dong sp. nov. in life A dorsal view B ventral view C dorsolateral view D ventral view of hand E ventral view of foot.

Figure 5. Colour variation in Leptobrachella dong sp. nov. A dorsolateral view of the male specimen CIB LB 20220311002 B dorsal view of the male specimen CIB SCC 1754 C dorsal view of the female specimen CIB LB 20220305005 D dorsal view of the female specimen CIB LB 20220306008.

Figure 6. Advertisement calls of Leptobrachella dong sp. nov. A, B waveform and sonogram of the first call type (type A) over 2 seconds of the paratype CIB LB 20220311002, respectively C, D waveform and sonogram of the second call type (type B) over 2 seconds of the holotype CIB SSC 1757, respectively.

Figure 7. The tadpole CIB WB 2020277 of Leptobrachella dong sp. nov. in life A dorsal view B lateral view C ventral view D oral disc.

Figure 8. Habitats of Leptobrachella dong sp. nov. A landscape of the type locality Tongdao County, Hunan Province, China B a torrent mountain stream in the type locality (insert holotype CIB SSC 1757 in life in the field) C habitat at the Congjiang County, Guizhou Province, China D habitat at the Suining County, Hunan Province, China.