Leptolalax dringi DUBOIS, 1987

Matsui, Masafumi & Dehling, Maximilian, 2012, Notes on an enigmatic Bornean megophryid, Leptolalax dringi Dubois, 1987 (Amphibia: Anura), Zootaxa 3317 (1), pp. 49-58 : 51-54

Leptolalax dringi DUBOIS, 1987

Dring’s Litter Frog

( Figures 1–3 )

Holotype. BMNH 1978.3 , an adult male, from Camp IV, southern flank of Gunung Mulu , Gunung Mulu National Park, Miri Division, Sarawak, Malaysia (Borneo), collected in August 1977 by Julian C. Dring.

Paratopotypes. BMNH 1978.2 , an adult female, BMNH 1978.4 , 1978.5 , two adult males; collected with the holotype .

Referred material. Topotypes: NMBE 1056369 , an adult female , NMBE 1056370 , 1056371 , 1056372 , 1056373 , four adult males, from a headwater of Sungai Tapin, southern flank of Gunung Mulu , Gunung Mulu National Park, Miri Division, Sarawak, Malaysia (Borneo), collected on 27 March 2009 by J. M. Dehling, S. T. Hertwig and Pui Y.-M.

Diagnosis. Leptolalax dringi is distinguishable from its congeners by the combination of the following characters: (1) size medium, SVL 26.6–31.3 mm in males and 36.6–38.1 mm in females, (2) head slightly wider than long, (3) snout acuminate in dorsal view, rounded in profile, (4) dorsum smooth with few scattered tubercles, (5) pectoral glands small and low, hardly discernible, (6) ventrolateral, supraaxillary, and femoral glands absent, (7) ventral side white to cream-coloured, mottled and spotted with dark marking, (8) dorsum light brown with dark brown markings lacking a light margin, (9) upper arm with colour pattern, (10) webbing between toes rudimentary, (11) advertisement call having a dominant frequency at 6.1–6.4 kHz and consisting of 2 to 11 notes, each with a mean duration of 14 ms and lacking evident frequency-modulation.

Description of holotype ( Figure 1 ). Measurements are given in Table 1 . Habitus moderately stocky; head moderately broad (HW/SVL 0.32), wider than long (HW/HL 1.14) and wider than trunk; snout acuminate in dorsal view, rounded in profile, slightly protruding, its length almost half the head length (SL/HL 0.46) and subequal to eye diameter (SL/ED 0.96); canthus rostralis distinct, slightly concave in dorsal view between eye and nostril, convex between nostril and tip of snout; loreal region oblique, concave; nostrils rounded, directed laterally, situated on a low projection; distance between eye and nostril smaller than internarial distance (EN/NN 0.77) and smaller than eye diameter (EN/ED 0.56); interorbital distance smaller than internarial distance (IO/NN 0.90) and smaller than upper eyelid width (IO/EW 0.85); pupil vertical; tympanum distinct, rounded, its diameter almost half eye diameter (TD/ED 0.49), separated from eye by about half its diameter; pineal spot visible, anterior to line connecting anterior corners of orbits; symphysial knob on anteriormost part of mandible; vomerine ridge and teeth absent; tongue large, broad, notched distally, free for about half its length; median lingual process absent; vocal sac median, subgular; vocal openings small, just posterior to rictus, close to eustachian tube openings.

Forelimbs slender, moderately short (ELB/SVL 0.68, ARM/SVL 0.51); hand longer than forearm (HND/ARM 0.53); fingers long and slender, without webbing or lateral fringes of skin ( Figure 2 ); relative length of fingers I<II<IV <III; finger tips rounded and thickened; subarticular tubercles indistinct, replaced by elongate callous tissue; nuptial pads absent; large, rounded, subquadratic, prominent tubercle in thenar and metacarpal region of fingers I and II, divided subequally in proximal and distal part by shallow superficial depression, separated by a distinct groove from smaller, subtriangular tubercle in metacarpal region of fingers III and IV.

Hindlimbs moderately long (LEG/SVL 1.65); tibiofibula moderately long (TFL/SVL 0.51), not much longer than foot (TFL/FOT 1.12) and longer than thigh (TFL/THL 1.09); heels overlapping each other when knees flexed and thighs held laterally at right angle to body; tibiotarsal articulation of adpressed limb reaching level of nostril; relative length of toes I<II<V<III<IV; toe tips rounded and thickened, smaller than finger tips; toe webbing rudimentary ( Figure 2 ); very narrow fringes of skin on lateral sides of toes except preaxial one of toe I and postaxial one of toe V, hardly discernible; subarticular tubercles replaced with longitudinal ridge of thickened skin on plantar side of toes, from base to distal half of penultimate phalanx; inner metatarsal tubercle oval, large (1.8 mm), slightly less than half length of first toe (3.9 mm); outer metatarsal tubercle absent.

Skin on dorsum shagreened with scattered small tubercles; lateral surface of trunk with several larger, low tubercles; skin on dorsal surfaces of extremities weakly wrinkled; wrinkles forming indistinct, reticulated, predominantly longitudinal, low ridges; supratympanic fold distinct, angular, running from posterior margin of eye to level of insertion of forelimbs; few enlarged tubercles at posterior end of rictus; ventral skin smooth; skin of gular region not modified; pectoral glands very small, very low, hardly discernible; supraaxillary and femoral glands and ventrolateral glandular ridges absent.

Colour in preservative. In preservative, colour and pattern have generally faded and colours have changed. Light brown dorsally on head and body, with discrete, dark brown spots lacking a light outline; subtriangular spot between eyelids, its corners being darker than centre which is almost as light as surrounding area; similar but smaller spot dorsally on snout, between levels of eyes and nostrils; two parallel dark brown stripes running from between nostrils to edge of upper jaw, separated from each other by light, cream-coloured stripe running between them; upper lip diffusely and irregularly barred with dark and light brown; tympanum appearing lighter than area surrounding it; black, triangular spot on both sides in loreal region between eye and nostril; sides of trunk with light-centered dark spots; groin with dark brown spot extending onto thigh; limbs marked dorsally with alternating light and dark brown crossbars, with dark ones being much narrower than light ones; dark crossbars restricted to postaxial side on upper arm; basic colouration on upper arm not markedly lighter than on lower arm; sides of tibia with dark brown spots, continuing as bars across dorsal surface; chin, throat, chest, and ventral side of thigh creamcoloured with fine, light brown mottling; mottling darker brown along edge of lower jaw; anterior part of abdomen cream-coloured with dark brown speckling, forming diffuse spots; posterior part of abdomen light cream-coloured without distinct pattern; posterior surface of thigh taupe with light brown speckles; iris greyish blue.

Colour in life (based on topotypes, Figure 3 ). During the day, colour pattern similar to that described for preserved holotype but colours more contrasting and vivid; ventral edge of supratympanic fold dark brown; pattern on ventral side brown to greyish; iris light red in upper third and along inner margin around pupil, and bluish silver with black reticulation in lower two-thirds. At night, olive brown dorsally on head and trunk, with indistinct dark brown markings, including interorbital marking; dark spot in loreal region; lips barred white and light grey; lateral sides of trunk with dark, light-centred spots; basic colouration on dorsal side of limbs greyish light brown; markings on limbs lighter than during the day; iris colouration somewhat darker at night than during the day.

Variation. Individuals of the type series are generally similar in morphology. Measurements of the paratopotypes and topotypes are given in Table 1 . Females (SVL 36.6–38.1 mm) are larger than males (SVL 26.6–31.3 mm). Snout length is slightly greater than eye diameter in one individual. Interorbital width is slightly greater than upper eyelid width in one individual and slightly greater than internarial distance in five individuals. Tibiotarsal articulation of adpressed limb reaches tip of snout in one male. Females have relatively shorter hindlimbs than males with tibiotarsal articulation reaching only between eye and the nostril.

Advertisement call ( Figure 4 ). The male advertisement call description is based upon the calls of one of the paratypes (BMNH 1978.4), recorded at unknown temperature. The advertisement call lasted 110–1040 (600.3+249.9, n=52) ms and emitted in long series ( Figure 4 A). Each call series lasted at least 3 s, with a call gap of 410–1390 (948.0+251.1, n=52) ms, and a call repetition rate of 0.88–1.19 (1.01+0.06, n=20) per second. A call consisted of a series of 2 to 11 (mean+SD = 6.73+2.41, n=52) distinct notes ( Figure 4 B, C). Each note lasted 7.2– 23.2 (14.2+4.8, n=68) ms with the note gap of 91.7–119 (101.0+4.2, n=57) ms ( Figure 4 D, E), and the note repetition rate of 8.16–10.34 (9.52+0.61, n=16) per s. Each note composed of 1–2 (1.49+0.50, n=68) distinct pulse or pulse groups ( Figure 4 D, E).The pulse length varied greatly from 2.2 to 5.3 (3.4+0.9, n=33) ms in the first pulse of the two-pulsed note. The second pulse was longer than the first, lasting from 4.4 to 8.8 (7.2+0.9, n=33) ms, and followed the first pulse with an interval of 0.6–13.2 (7.4+4.2, n=33) ms. The frequency range was wide ( Figure 4 B), from 5.8 to 6.7 (lower = 5.9+0.9 and upper = 6.5+1.6, n=11) kHz, and the dominant frequency ranged from 6050 to 6400 (6182.5+67.7, n=68) Hz ( Figure 4 F). Frequency and intensity modulation were not evident within a single note, while slight frequency and clear intensity modulation was irregularly observed within a call ( Figure 4 A, B). Harmonics and fundamental frequency were not traced.

Figures

FIGURE 1. Dorsal (A), ventral (B), and lateral (C) views of a male holotype of Leptolalax dringi (BMNH 1978.3) (photos: Colin McCarthy). Scale bar represents 1 cm.

FIGURE 2. Plantar view of left foot (left) and volar view of left hand (right) of the holotype of Leptolalax dringi (BMNH 1978.3). Scale bar indicates 5 mm (photos: JMD).

FIGURE 3. Topotypes of Leptolalax dringi in life. (A) Dorsolateral view in situ during the night (NMBE 1056372); (B) dorsolateral view during the day (NMBE 1056369); (C) ventral view during the day (NMBE 1056369) (photos: JMD).

FIGURE 4. Advertisement call of Leptolalax dringi (paratype BMNH 1978.4) recorded at unknown temperature. (A) 45 s oscillogram of relative amplitude over time for 41 calls. (B) spectrogram and (C) corresponding oscillogram of two successive calls each containing 11 and nine notes, expanded from the section pointed by arrow in A. (D) spectrogram and (E) corresponding oscillogram of the first three notes in B, each containing one, one, and two pulses, respectively. (F) power spectrum (relative amplitude vs. frequency) of first note shown in D – E.

Tables

TABLE 1. Measurements of type series and topotypes of Leptolalax dringi (in mm). For abbreviations see Material and methods.

Vo u c h e r No. Sex	BMNH 1978.3 male	BMNH 1978.4 male	BMNH 1978.5 male	NMBE 1056370 male	NMBE 1056371 male	NMBE 1056372 male	NMBE 1056373 male	BMNH 1978.2 female	NMBE 1056369 female
Status	holotype	paratype	paratype	topotype	topotype	topotype	topotype	paratype	topotype
SVL	31.3	29.6	29.8	28.2	26.6	29.4	28.6	38.1	36.6
TFL	15.9	15.3	15.2	15.4	15.0	15.3	15.2	18.7	17.9
FOT	14.2	13.6	12.9	13.0	12.4	13.6	13.0	16.9	15.3
TarL	23.0	22.1	21.7	21.8	21.0	21.7	21.3	27.6	26.3
LEG	51.8	48.7	49.2	48.6	47.3	48.7	48.7	61.2	58.9
THL	14.6	14.0	14.0	14.2	14.1	14.6	14.5	16.5	16.9
ELB	21.4	19.4	20.2	21.0	20.6	20.8	20.7	25.5	25.0
ARM	15.9	14.8	15.1	15.1	15.1	15.4	15.0	18.9	18.6
HND	8.4	8.3	7.8	7.8	7.3	8.0	7.5	9.6	9.3
1FL	4.5	4.8	4.3	4.3	4.1	4.7	4.4	5.7	5.4
2FL	5.1	5.0	5.4	4.9	4.9	5.4	4.9	6.2	6.4
4FL	6.3	6.0	5.6	5.7	5.6	5.7	6.0	7.1	7.3
IMT	1.8	1.7	1.7	1.7	1.7	1.6	1.7	2.6	2.5
HW	10.0	9.9	10.1	10.1	9.9	9.8	10.1	12.6	13.1
HL	8.8	8.5	9.0	8.3	8.1	8.5	8.8	11.0	11.7
IO	2.7	3.1	2.7	2.6	2.7	2.9	2.9	3.2	3.5
EW	3.2	3.0	3.4	3.2	3.2	3.2	3.2	4.3	4.4
ED	4.2	4.3	4.3	3.9	3.9	3.8	4.0	5.3	5.1
TD	2.0	2.4	2.4	2.2	2.0	2.5	2.4	2.8	2.9
TE	1.3	1.3	1.2	0.9	1.2	1.2	1.1	1.6	1.5
EN	2.4	2.3	2.5	2.2	2.3	2.3	2.4	2.8	2.7
NS	2.4	2.5	2.5	2.1	2.1	2.1	2.0	2.7	2.6
SL	4.0	3.8	3.9	4.0	3.8	3.8	3.9	5.0	4.8
NN	3.1	3.0	2.9	2.6	2.6	2.9	2.7	3.5	3.0