Leptolalax gracilis ( Günther, 1872 )

Dehling, Maximilian, 2012, Redescription of Leptolalax gracilis (Günther, 1872) from Borneo and taxonomic status of two populations of Leptolalax (Anura: Megophryidae) from Peninsular Malaysia, Zootaxa 3328, pp. 20-34 : 21-28

Leptolalax gracilis ( Günther, 1872)

Slender Litter Frog

( Figures 1–4 )

Leptobrachium gracile — Günther 1872, Boulenger 1882

Megalophrys gracilis — Boulenger 1908b, Boulenger 1912 (partim)

Megophrys gracilis — Smith 1930 (partim)

Leptobrachium gracilis — Inger 1966

Leptobrachium (Leptolalax) gracile — Dubois 1980 Leptolalax gracilis — Dubois 1983

Holotype: BMNH 72.2.19.35 = 1947.2.25 , an adult female, collected by Alfred A. Everett at Matang, Sarawak, Borneo.

Referred material: NMBE 1059912 , an adult female, NMBE 1056599 , 1056602 , 1056604 , 1059903 – 1059911 , twelve adult males; all from Kubah National Park , Matang Range, Sarawak, Borneo, collected by J. M. Dehling in April and September 2009.

Diagnosis: The type species of the genus Leptolalax ( Dubois 1980) , distinguishable from its congeners by the combination of the following characters: (1) size large, SVL of males 34.3–39.0 mm, of females 42.4–49.0 mm, (2) interorbital distance less than or subequal to width of upper eyelid, (3) pectoral glands small and low, hardly discernible, (4) ventrolateral, supra-axillary, and femoral glands absent, (5) venter speckled with large, irregularly shaped spots, (6) snout acuminate in ventral view, rounded in lateral view, (7) webbing between toes basal, (8) advertisement call consisting of long series of notes with 3–4 pulses, dominant frequency at 2600–2800 Hz, without frequency-modulation.

Description of the holotype ( Figure 1 ): Habitus slender; head broad (HW/SVL 0.36), wider than long (HW/ HL 1.12) and wider than trunk; snout acuminate in ventral view, rounded in lateral view, slightly protruding, its length two-fifths the head length (SL/HL 0.41) and shorter than eye diameter (SL/ED 0.93); canthus rostralis distinct, almost straight-lined in both dorsal and lateral view; loreal region oblique, moderately concave; nostrils rounded, directed laterally; distance between eye and nostril slightly larger than internarial distance (EN/NN 1.06) and smaller than eye diameter (EN/ED 0.63); pupil vertical; tympanum distinct, rounded, its diameter two-fifths the eye diameter (TD/ED 0.42); interorbital distance subequal to eyelid width (IO/EW 0.99); pineal ocellus absent; symphysial knob on anteriormost part of mandible; vomerine ridge and teeth absent; tongue large, broad, bifid, free for about half its length; median lingual process absent.

Fore limbs slender, moderately long (ELB/SVL 0.76, ARM/SVL 0.56); hand about as long as forearm (HND/ ARM 0.49); fingers long and slender, without webbing or lateral fringes of skin ( Figure 2 ); relative length of fingers IV<II<I<III; finger tips rounded and thickened; subarticular tubercles indistinct; large, rounded, prominent tubercle in metacarpal region of fingers I and II; much smaller tubercle in metacarpal region of fingers III and IV.

Hind limbs moderately long (LEG/SVL 1.66); tibiofibula long (TFL/SVL 0.53), much longer than foot (TFL/ FOT 1.34) and longer than thigh (TFL/THL 1.08); heels overlapping each other considerably when knees are flexed and thighs are held laterally at right angle to body; toe tips rounded and thickened, smaller than finger tips; toes webbed at bases only ( Figure 2 ); very narrow fringes of skin on lateral sides of toes except preaxial side of toe I and postaxial side of toe V; relative length of toes I<II<V<III<IV; subarticular tubercle on toes I and II, and indistinct proximal one on toe V, replaced on toes III and IV with longitudinal ridge of thickened skin on the plantar side of phalanges except the distal ones; inner metatarsal tubercle oval, large, about half the length of toe I; outer metatarsal tubercle absent.

Skin on dorsum mostly smooth in preservative, weakly wrinkled on dorsal surfaces of the extremities; wrinkles forming indistinct, reticulated, predominantly longitudinal, low ridges; supratympanic fold distinct, curved, running from posterior margin of eye to just behind the corner of the mouth; ventral skin smooth; pectoral glands small, very low, hardly discernible, at the insertion of the forelimbs; supraaxillary glands and ventrolateral glandular ridges absent.

Variation: Measurements of holotype and topotypes are given in Table 1. A female topotype is larger than the holotype but generally similar in proportions ( Table 2 ). Males are smaller than females but similar in proportions ( Tables 1 , 2 ). Males have single, median, subgular vocal sacs. The skin of the dorsum is granular with many small tubercles in life but smooth in preservative. The wrinkles on the dorsal surfaces of the extremities are more discernible in life than in preservative.

Colouration in life (based on topotypes): Basal colouration of the dorsum variable between individuals and also within a single individual at different times of the day; from light grey, cream-coloured, or yellowish to dark grey or almost black ( Figure 3 ). Basal colouration of the venter is white. Several colour pattern elements present on body. Their colouration is darker than the sourrounding areas and varies from grey to brown or black. Dark dorsal pattern variable but often consisting of a broad, interrupted line running from tympanum to groin on both sides of the body. Another line runs above the spine in some individuals; in others, this line is reduced to a series of irregularly shaped spots. Some individuals lack a dorsal pattern. The lateral sides of the body have large dark spots in most individuals. In some, there are also small, cream-coloured dots. Dark spots are also present on the lateral sides of the thigh and tibia, above the tympanum and in the loreal region. A large, Y-shaped blotch is present between the eyelids in most individuals, as are two oval, anterolaterally directed spots on the snout, one of each side posterior to the nostrils. These spots can be fused with each other partially or completely, forming V-shaped or triangular blotches. The lips are irregularly barred light and dark, with pattern in the supralabial area being continued in the infralabial area. Legs and lower arms are banded. In most individuals, the bands are darker than the surrounding areas; in some individuals, however, they can become light grey during the night and then are about as light as or even lighter than the surrounding areas ( Figure 3 ). The upper arm and the proximal one-fourth of the lower arm are cream-coloured in most individuals without any pattern or with only small dots. In few individuals the upper arm is dark-banded like the lower arm. The ventral sides of foot, tarsus, and lower arm are dark grey or black. Venter, chest and chin are spotted with large dark spots ( Figure 4 ). In some individuals, the ventral pattern can become quite weak during the night, and is more apparent during the day. The iris is bright red in the upper two-fifths and dull greyish red, with a narrow ring of bright red along the pupil in the lower three-fifths.

Colouration in preservative: Similar to that in life but colours are generally paler. Dorsal and ventral patterns are clearly visible.

Ecological notes: The species is abundant at the lower elevations (<500 m) of Gunung Serapi in the Matang Range. Individuals can be found in the leaf litter of the forest floor from only a few to several dozens of meters from the next stream. They are seldom found on leaves in the vegetation. Males call from the forest floor but sometimes can be found perched on elevated calling sites like a fallen tree, a tree root, or a rock, up to 2 m above the ground. Characteristics of the advertisement call of topotypic specimens have been reported by Matsui (1997).

Etymology: From Latin gracilis , meaning “slender”. In allusion of the slender limbs of the species in comparison to those of Leptobrachium hasseltii , according to the original publication.

Figures

FIGURE 1. Dorsal view (left) and ventral view (right) of the female holotype of Leptolalax gracilis (BMNH 72.2. 19.35 = 1947.2.25). Scale bar represents 10 mm.

FIGURE 2. Volar view of left hand (left) and plantar view of left foot (right) of a female topotype of Leptolalax gracilis (NMBE 1059912). Not to scale.

FIGURE 3. Lateral view of four topotypic specimens of Leptolalax gracilis in life, showing the variation in colouration. Not to scale.

FIGURE 4. Ventral view of four topotypic males of Leptolalax gracilis, showing the variation in colour pattern. Not to scale.

Tables

TABLE 1. Body measurements of holotype and topotypic specimens of Leptolalax gracilis and adult specimens of Leptolalax sp. 1 (in mm). Values for male L. gracilis are given as mean ± standard deviation, followed by range. For abbreviations see Material and methods.

species	Leptolalax gracilis	Leptolalax gracilis	Leptolalax gracilis	Leptolalax sp. 1	Leptolalax sp. 1
Voucher No.	BMNH 72.2.19.35 = 1947.2.25	NMBE 1059912	NMBE 1056599, 1056602, 1056604, 1059903– 1059911	BMNH 1967.2297	BMNH 1967.2298
sex	female	female	males	female	male
status	holotype	topotype	topotypes
origin	Matang Range, Borneo	Gunung Serapi, Matang Range, Borneo	Gunung Serapi, Matang Range, Borneo	Gunung Benom, Pahang	Gunung Benom, Pahang
SVL	42.4	49.3	37.2 ± 1.5 34.3–39.0	46.0	35.1
TFL	22.7	24.4	20.0 ± 1.3 17.6–21.8	24.7	17.1
FOT	17.0	20.6	16.6 ± 1.0 14.8–18.3	21.0	14.8
TarL	31.4	33.4	27.3 ± 2.0 22.6–30.0	33.9	24.7
LEG	70.3	76.2	62.5 ± 4.0 54.1–68.9	75.8	55.8
KNE	41.9	46.1	37.1 ± 2.0 33.2–39.8	43.4	32.6
ELB	32.1	34.3	27.7 ± 1.6 25.6–30.4	33.2	23.1
ARM	24.0	25.1	20.5 ± 1.2 18.5–22.5	25.9	18.3
HND	11.8	12.1	10.1 ± 0.8 8.8–11.5	13.9	9.6
HW	15.1	14.7	12.3 ± 0.7 11.3–13.7	17.5	13.0
HL	13.5	15.6	12.2 ± 0.6 11.5–13.3	14.7	11.1
IO	4.1	4.2	3.5 ± 0.2 3.2–3.9	5.7	4.0
EW	4.2	5.5	4.4 ± 0.3 3.9–5.0	4.5	3.5
ED	5.9	6.3	5.3 ± 0.4 4.8–5.9	5.4	4.5
TD	2.5	3.5	2.6 ± 0.3 2.1–3.0	2.6	1.8
SL	5.5	6.6	5.4 ± 0.4 4.7–6.0	7.2	5.3
EN	3.7	3.9	3.3 ± 0.2 2.7–3.6	4.5	3.4
NN	3.5	3.6	3.2 ± 0.2 2.8–3.4	4.7	3.4

TABLE 2. Body proportions of holotype and topotypic specimens of Leptolalax gracilis. Values for males are given as mean ± standard deviation, followed by range. For abbreviations see Material and methods.

species	Leptolalax gracilis	Leptolalax gracilis
Voucher No.	BMNH 72.2.19.35 = 1947.2.25, NMBE 1059912	NMBE 1056599, 1056602, 1056604, 1059903–1059911
sex	females	males
status	holotype, topotype	topotypes
origin	Matang Range, Borneo	Matang Range, Borneo
TFL/SVL	0.50–0.53	0.54 ± 0.02 0.51–0.57
Fot/SVL	0.40–0.42	0.44 ± 0.01 0.42–0.47
TarL/TFL	1.37–1.38	1.37 ± 0.04 1.28–1.43
HW/SVL	0.30–0.36	0.33 ± 0.01 0.32–0.35
HL/SVL	0.32	0.33 ± 0.01 0.31–0.34
KNE/TFL	1.85–1.89	1.86 ± 0.03 1.83–1.91
LEG/SVL	1.55–1.66	1.68 ± 0.06 1.58–1.79
ELB/SVL	0.69–0.76	0.74 ± 0.02 0.70–0.79
HND/SVL	0.24–0.28	0.27 ± 0.01 0.25–0.30
SVL/IO	10.30–11.63	10.65 ± 0.42 9.96–11.27
IO/HW	0.27–0.29	0.28 ± 0.01 0.26–0.30
NN/HW	0.23–0.25	0.26 ± 0.01 0.24–0.28
SVL/NN	12.12–13.58	11.74 ± 0.48 11.14–12.72
HW/HL	0.94–1.12	1.01 ± 0.03 0.96–1.06
KNE/SVL	0.94–0.96	1.00 ± 0.03 0.96–1.05
IO/EW	0.78–0.99	0.79 ± 0.05 0.71–0.89
ED/SL	0.95–1.07	0.98 ± 0.03 0.94–1.04
EN/NN	1.05–1.06	1.03 ± 0.07 0.92–1.17
ED/EN	1.59–1.64	1.63 ± 0.09 1.45–1.78
EN/HL	0.25–0.27	0.27 ± 0.02 0.24–0.29
ED/TD	1.78–2.36	2.09 ± 0.16 1.91–2.42
ED/HL	0.40–0.44	0.43 ± 0.02 0.41–0.47