Leptolalax applebyi, Rowley, Jodi J. L. & Trung, Cao Tien, 2009

Rowley, Jodi J. L. & Trung, Cao Tien, 2009, A new species of Leptolalax (Anura: Megophryidae) from central Vietnam, Zootaxa 2198, pp. 51-60 : 52-59

Leptolalax applebyi sp. nov.

Holotype: AMS R171703, an adult male, calling in leaf litter, 2 m from steep, narrow, rocky stream in Song Thanh Proposed Nature Reserve, Phouc Son district, Quang Nam Province, Vietnam (15.27394 º N, 107.76015 º E, 1402 m; Figure 1 ). Collected at 18:15 h on 23 July, 2007 by the authors.

Paratypes: AMS R 171704–171706 adult males from type locality ( Figure 1 ), collected between 18:16– 18:30 h on 23 July, 2007. All males were calling. AMS R 171707, one adult female collected at 19:00 h, on 24 July, 2007, from 15.26253 º N, 107.75759 º E, 1312 m. All specimens were found 1–2 m from steep, narrow, rocky streams in evergreen forest.

Etymology: specific epithet is a patronym honouring Robert Appleby, an investor in biodiversity conservation and scientific capacity building in Asia.

Diagnosis: Assigned to the genus Leptolalax on the basis of the following: small size, the presence of an elevated thenar tubercle not continuous to the thumb, chest glands present but not forming teats, vomerine teeth absent, anterior tip of snout with vertical white bar (Dubois 1980; Lathrop et al. 1998). Leptolalax applebyi is distinguished from its congeners by a combination of (1) body size (19.6–20.8 mm for five adult males; 21.7 mm for single adult female), (2) uniformly smooth dorsum lacking tubercles, (3) dark brown dorsal surface lacking distinct patterns and dark brownish pink ventral surface with white speckling (4) an absence of webbing and dermal fringes on fingers, (5) slight basal webbing and no dermal fringes on toes (6) short tibia (TIB:SVL 0.466–0.480), and (7) unique advertisement call consisting of 4–5 notes with a dominant frequency of 3962.1–4306.6 Hz, repeated at a rate of approximately 9 notes per second.

Description of holotype: Head longer than wide; snout rounded or truncate in profile, projecting slightly over lower jaw; nostril closer to tip of snout than eye; canthi rostralis rounded, constricted; lores sloping, concave; vertical pupil; diameter of eye less than length of snout; tympanum distinct, round, diameter smaller than that of the eye; anterioventral three-quaters of tympanic rim slightly elevated relative to skin of temporal region; vomerine teeth absent; pineal ocellus absent; vocal sac openings absent; tongue large, broad, and weakly notched posteriorly; weak supratympanic ridge running from eye towards axilla. Tips of fingers rounded, slightly enlarged; relative finger lengths I<II=IV<III; nuptial pad absent; subarticular tubercles absent; a large, round inner palmar tubercle distinctly separated from small, laterally compressed outer palmar tubercle; no finger webbing or lateral fringes. Tips of toes like fingers; relative toe length I<II<V<III<IV; subarticular tubercles absent, replaced by dermal ridges, distinct on second, third and fourth toes; small, oval inner metatarsal tubercle pronounced, outer metatarsal tubercle absent; webbing basal, confined to very base of toes; no lateral fringes. Tibia short and stout, width approximately one-third of length; tibiotarsal articulation reaches anterior corner of eye. Skin on dorsal and ventral surfaces smooth, only eyelid with low, indistinct tubercles; pectoral gland small, indistinct, circular; femoral gland distinct, small white, on posteroventral surface of thigh, closer to knee than to vent; small gland above axilla; no ventrolateral glandular ridge.

Colour of holotype in life: Dorsal surface dark brown with indistinct, diffuse darker brown patch between axillae; vertical darker brown bars on upper lip, indistinct lighter vertical stripes at tip of snout and under eyes; no interorbital bar; black line along canthus rostralis, through eye, and continuing along supratympanic ridge, encompassing most of tympanum, terminating above axilla; transverse darker bars on dorsal surface of limbs; large, black blotch on posterior flank anterior to sacrum and two smaller black spots on lateral flank; ventral surface of elbow and upper arm without dark bars, indistinct paler colouration on elbow; fingers with indistinct transverse barring; ventral surface dark brownish pink, with white speckling concentrated on belly, but also on throat, ventral surfaces of arms, tibio-tarsus and feet; fine white speckling extends to ventrolateral surface of belly and on lower margins of head, with a single distinct and slightly larger white spot just posterior to tympanum; ventral margin of throat bearing row of larger white spots. Macroglands white. Iris coppery gold, with minute, black reticulations.

Colour of holotype in preservative: Dark brown dorsal surface. Ventral surface pale brown with white speckling and white macroglands. Colours faded.

Measurements: Holotype: SVL 19.6, HDL 7.4, HDW 6.6, SNT 3.0, EYE 2.0, IOD 2.6, TMP: 1.1, TEY 0.7, TIB 9.2, weight 0.8g

Variation: Specimens vary in dorsal colouration, from uniformly coloured dark brown (AMS R 171706) to weakly mottled (AMS R 171704–5). Dark barring on limbs may be indistinct and diffuse (AMS R 171706). Female (AMS R 171707) pale brown with diffuse darker chevrons on dorsum, above axilla. Paler vertical stripes at tip of snout and under eyes vary from indistinct (AMS R 171706) to distinct (AMS R 171704–5), most distinct in the single female (AMS R 171707). Ventral surface of chest and belly may be white with dark speckling in places, as opposed to all dark with white speckling. Female (AMS R 171707) has slightly paler throat. Elbows of female (AMS R 171707) and one male (AMS R 171705) are distinctly paler. Colouration on dorsal surface of head between the snout and eyes may be slightly paler. Iris colour varies from uniform gold to uniform reddish copper. Black spots on lateral flank variable in number (1–4 spots), size and shape. Female (AMS R 171707) has black spot on left knee. Tibiotarsal articulation reaches between anterior corner of eye and nostril. In life, males weighed 0.8–0.9g. Female, with distinct follicles present in ovary, weighed 1.0 g in life. Measurements of the type series are shown in table 1.

Advertisement call: Call descriptions are based on the calls of the holotype and a non-vouchered individual, both taken at 21.5ºC ambient temperature. Calls consisted of 4–5 notes, repeated at a rate of approximately 9 per second, with each note consisting of between one and five distinct pulses (Table 2, Figures 4 A, C). There was little frequency modulation, with the dominant frequency between 3962.1–4306.6 Hz ( Figures 4 B, D), and harmonics at approximately 7752 Hz. Pulse duration was between 2–7 ms. To the human ear, the call of L. applebyi sounds like a faint, rapid rasping, similar to an orthopteran. The calls of L. applebyi and L. tuberosus differ considerably in structure and frequency (Rowley & Cao, unpublished data).

Males Female R171703 R171704 R171705 R171706 R171707 Ecology: All specimens were found at the headwaters of rocky streams in medium montane forest (evergreen forest between 1200–1500m; Tordoff et al. 2003). Streams were steep, narrow (<2 m wide) and had little water flow. Despite intensive surveys, L. applebyi was never heard or observed below 1300 m elevation. Male L. applebyi were found calling from under leaf litter, always approximately 2 m from the stream. Leptolalax applebyi was found in sympatry with L. tuberosus . Leptolalax tuberosus was more widely distributed in terms of elevation, with individuals collected between 863–1401 m, and was almost always found greater than 5 m distance from streams. The stomach contents of AMS R171707 included remains of a small cockroach (order Blattaria).

* holotype

Conservation status: The five type specimens are the only known representatives of the new species. Given the available information, we suggest the species should be considered Data Deficient following IUCN’s Red List categories ( IUCN 2001). Being known from only two localities approximately 1.3 km apart, its extent of occurrence is unknown but probably more widespread. The known habitat of L. applebyi falls within a protected area and is remote and steep enough that immediate deforestation risk is likely low. The habitat of L. applebyi is also contiguous with similar areas of habitat in the central Truong Son landscape ( Tordoff et al. 2003), including Ngoc Linh Nature Reserve in Kon Tum Province to the south, and Laos in the west, but areas above 1200 m elevation compose only 8.5% of existing forest in the Truong Son landscape and are patchily distributed ( Tordoff et al. 2003).

Comparisons: Leptolalax applebyi is distinguished from all other described Leptolalax species by a combination of (1) body size (19.6–20.8 mm for five adult males; 21.7 mm for single adult female), (2) uniformly smooth dorsum lacking tubercles, (3) dark brown dorsal surface lacking distinct patterns and dark brownish pink ventral surface with white speckling (4) an absence of webbing and dermal fringes on fingers, (5) slight basal webbing and no dermal fringes on toes, (6) short tibia (TIB:SVL 0.466–0.480), and (7) unique advertisement call consisting of 4–5 notes with a dominant frequency of 3962.1–4306.6 Hz, repeated at a rate of approximately 9 notes per second.

Leptolalax applebyi is one of the smallest species in the genus. Two species of Leptolalax have overlapping male adult body sizes; L. pluvialis , known only from northern Vietnam at 21.3–22.3 mm, and the recently described Leptolalax kecil from the Malay Peninsula, at 19.3–20.5 mm. Similar body sizes have been reported for L. alpinis (24.0–26.4), L. heteropus (24.0– 33 mm), L. liui (23.0– 28.7 mm) and L. tuberosus (24.4–29.5 mm). All other species have considerably larger male body sizes ( L. arayai 29.6 mm; L. bouretti 27.2–36.2 mm; L. dringi 28.7–30.3 mm; L. fulignosus 28.2–30.0 mm; L. gracilis 31–39 mm; L. hamidi 28.7– 31.3 mm; L. kajangensis 34–35 mm; L. lateralis 26.9–28.3 mm; L. maurus 26.1 mm; L. melanolectus 26.6– 28.8 mm; L. nahangensis 40.8 mm; L. oshanensis 26.6–30.7 mm; L. pelodytoides 37 mm; L. pictus up to 36 mm; L. solus 30–35 mm; L. sungi 48.3–52.7 mm; L. ventripunctatus 25.5–28.0 mm).

The single female specimen of L. applebyi (21.7 mm) does not fall within the range of female body sizes reported in the genus to date ( L. alpinis 32.1 mm; L. bouretti 42.0–45.0 mm; L. dringi 37.5 mm; L. gracilis 40–41 mm; L. hamidi 36.1–42.8; L. kecil 25.0 mm, L. lateralis 36 mm; L. liui 23.1–28.1 mm; L. maurus 31.8 mm; L. melanolectus 32.7 mm; L. oshanensis 31.6 mm; L. pictus up to 47 mm; L. sungi 56.7–58.9 mm; L. tuberosus 30.2 mm).

The skin texture and colouration of L. applebyi differs from all previously described Leptolalax species. In terms of skin texture, only L. applebyi , L. pluvialis , L. heteropus , L. pictus and L. kajangensis have a smooth dorsum lacking tubercles or dorsal ridges. Of these species, L. applebyi is the only species with a dark brown dorsal surface lacking distinct dorsal patterns ( L. heteropus and L. pictus have extensive, distinct dorsal markings or patches, L. pluvialis has distinct black interorbital markings and L. kajangensis has almost black dorsal surfaces with minute pale spots). Additionally, most Leptolalax species lacking a smooth dorsum also differ from L. applebyi in terms of dorsal colour and pattern ( L gracilis and L. hamidi have extensive, distinct dorsal markings or patches, L. arayai , L. fulignosus , L. kecil , L. lateralis , L. melanoleucus , L. nahangensis , L. oshanensis and L. sungi have distinct black interorbital markings, L. maurus has almost black dorsal surfaces and L. tuberosus has a sandy dorsum with an olive brown hatching pattern).

The dark brownish pink ventral surface with white speckling of L. applebyi is also distinctly different from other species in the genus ( L. alpinis , L. arayai , L. bouretti , L. dringi , L. fulignosus , L. gracilis , L. hamidi , L. lateralis , L. liui , L. nahangensis , L. oshanensis , L. pelodytoides , L. pictus , L. solus , L. sungi and L. tuberosus have entirely or mostly white or pale grey venters; L. pluvialis has a grey venter with dark grey marbling, uniform pale grey throat with speckling around the border and large whitish grey pectoral glands; L. melanolectus and L. ventripunctatus display large patches of distinct black and white marbling, L. heteropus has a grey venter, speckled with black; L. maurus has a black or dark grey brown venter, with indistinct small light areas, and L. kecil has a uniformly dark venter with large, dark orange pectoral glands).

In lacking webbing and dermal fringes on fingers and having only slight basal webbing and no dermal fringes on toes, L. applebyi is distinguished further from L. alpinis , L. bouretti , L. dringi , L. fulignosus , L. hamidi , L. heteropus , L. kecil , L. liui , L. pelodytoides , L. pluvalis , L. solus and L. sungi , all of which have dermal fringes or extensive webbing.

The relative tibia length of L. applebyi (TIB:SVL 0.47–0.48) distinguishes it from L. kucil (males 0.56– 0.58) L. pluvialis (0.52–0.56) L. pelodytoides (0.56), L. arayai (0.62), and L. kajangensis (0.42).

The advertisement call of L. applebyi also differs from the twelve Leptolalax species with described calls; L. arayai , L. dringi , L. fuliginous , L. gracilis , L. hamidi , L. heteropus , L. kecil , L. melanoleucus , L. pelodytoides , L. pictus and L. oshanensis , L. solus . Whereas the advertisement calls of L. gracilis , L. heteropus , L. kecil , L. pelodytoides , and L. solus overlap with L. applebyi in terms of number of notes per call, compared to L. applebyi , the calls of L. gracilis , L. heteropus and L. solus have much lower dominant frequencies (2540–3200Hz) and L. pelodytoides has higher dominant frequencies (6350–8100Hz). The advertisement call of L. kecil has both a lower dominant frequency, a lower number of pulses per note, and higher intercall interval compared to L. applebyi .

Figures

FIGURE 1. Type locality of Leptolalax applebyi sp. nov. (black circle), central Vietnam.

FIGURE 4. Advertisement call of L. applebyi sp. nov. (holotype AMS R 171703) recorded at ambient air temperature of 21.5 º C. (A) a 3 s waveform of relative amplitude, (B) corresponding 3 s spectrogram, (C) expanded, 0.27 s waveform and (D) corresponding spectrogram for same call.