Leptolalax (Lalos) nyx, Ohler & Wollenberg & Grosjean & Hendrix & Vences & Ziegler & Dubois, 2011

Ohler, Annemarie, Wollenberg, Katharina C., Grosjean, Stéphane, Hendrix, Ralf, Vences, Miguel, Ziegler, Thomas & Dubois, Alain, 2011, Sorting out Lalos: description of new species and additional taxonomic data on megophryid frogs from northern Indochina (genus Leptolalax, Megophryidae, Anura) 3147, Zootaxa 3147 (1), pp. 1-83 : 46-50

Leptolalax (Lalos) nyx n. sp.

( Fig. 19–20 )

Leptolalax bourreti — Bain & Nguyen 2004: 5; Frost et al. 2006: 50.

Onymophoront, by present designation: holophoront (holotype), AMNH A163810 , adult male, SVL 26.9 mm .

Other protaxonts (paratypes): AMNH A163814-6 , A163820–1 , A163825–7 , A163831 , IEBR 1121–1122 , 1124 , 1129–1130 , 1134 , 1137 , 1142–1143 , 1145 , adult males and adult females .

Onymotope: Cao Bo Commune, Vi Xuyen District , Ha Giang Province, Vietnam. Collected by Nguyen Quang Truong & Raoul H. Bain, 8 May 2000 .

Comment. A specimen for which DNA sequences were available from Vietnam was tentatively allocated to L. bourreti ( Bain & Nguyen 2004; Frost et al. 2006). It is morphologically quite distinct from the latter species, in particular in adult size and colour pattern. In the phylogram, bourreti appears polyphyletic. This member of the lineage is here described as a new species, which is the sister taxon of an unsupported clade composed of L. aereus , L. minimus and L. ventripunctatus .

Diagnosis. Member of the subgenus Lalos based on the presence of a lateroventral gland and molecular phylogenetic relationships ( Fig. 4 ), distinguished from other species included in this subgenus by the following combination of characters: moderate-sized species (males 26.7–32.6 mm; females 37.0–41.0 mm) ( Table 3) with rudimentary webbing and no fringes on toes; tympanum distinct; lateroventral glandular ridge poorly distinct; dermal ridges under toes rather poorly distinct; finger tips enlarged; dorsal skin with flat glandular warts (Table 4); dorsum greyish-brown with dark regularly set rounded spots; poorly distinct spots on flanks; ventral side whitish with brown borders; iris colour not known ( Table 5).

Description of the holophoront, adult male AMNH A163810. Size and general aspect: (1) Specimen of rather small size (SVL 26.9 mm), body rather robust.

Head. (2) Head of medium size, narrower (HW 9.0 mm) than long (HL 9.5 mm; MN 9.2 mm; MFE 7.6 mm; MBE 4.0 mm), flat. (3) Snout slightly protruding, its length (SL 4.2 mm) as long as horizontal diameter of eye (EL 4.2 mm). (4) Canthus rostralis rounded, loreal region concave, virtually vertical. (5) Interorbital space convex, as large (IUE 3.1 mm) as upper eyelid (UEW 3.1 mm) but larger than internarial distance (IN 2.6 mm); distance between front of eyes (IFE 5.1 mm) about three-fifths of the distance between back of eyes (IBE 8.8 mm). (6) Nostrils rounded, closer to tip of snout (NS 1.6 mm) than to eye (EN 1.8 mm). (8) Tympanum (TYD 1.7 mm) distinct, rounded; less than half eye diameter, tympanum-eye distance (TYE 1.0 mm) two-thirds of its diameter. (11) Tongue large, cordate.

Forelimbs. (12) Forearm short, thin (FLL 7.5 mm), longer than hand (HAL 7.1 mm), not enlarged. (13) Fingers long and thin (TFL 4.0 mm). (15) Tips of fingers rounded, enlarged. (16) Fingers without dermal fringe.

Hindlimbs. (19) Shanks about four times longer (TL 12.4 mm) than wide (TW 3.1 mm), longer than thigh (FL 12.0 mm) but shorter than distance from base of internal metatarsal tubercle to tip of toe IV (FOL 12.6 mm). (20) Toe IV (FTL 7.1) longer than third of distance from base of tarsus to tip of toe IV (TFOL 19.3 mm). (22) Tips of toes not enlarged. (23) Webbing rudimentary: I 2 – 2 ¼ II 2 – 3 III 2 2 /3 – 4 IV 4 – 2 ¾ V (MTTF 4.5 mm; MTFF 4.2 mm; TFTF 7.6 mm; FFTF 8.3 mm). (24) Dermal fringe along toe V absent. (26) Inner metatarsal tubercle rather long and prominent; its length (IMT 1.5 mm) 1.5 times in length of toe I (ITL 2.3 mm). (27) Tarsal fold absent.

Skin. (29) Dorsal and lateral parts of head and body: snout and side of head smooth; region between eyes, back and flanks with flat glandular warts, quite indistinct on dorsal part. (30) Supratympanic fold prominent, from eye to above shoulder. (31) Dorsal parts of limbs: forelimbs, thigh, shank and tarsus smooth with sparse indistinct glandular warts. (32) Ventral parts of head, body and limbs: throat, chest, belly and thigh smooth; posterior part of thigh with glandular warts. (33) Presence of macroglands: lateroventral glands present as a short chaplet of poorly distinct, separate glands on both sides of vent; distinct rounded rather small femoral, axillary and suprabrachial glands.

Coloration. In alcohol: (34) Dorsal and lateral parts of head and body: dorsal parts of head and dorsum, and upper part of flanks greyish-brown with a brown W-shaped pattern in the shoulder region continued as a poorly defined band on middorsum, all back covered with sparsely set white spots (corresponding to warts) with dark brown outline; lower part of flanks light brown with poorly distinct dark brown spots; loreal region brown; tympanic region including tympanum beige with a brown line under supratympanic fold covering upper half of tympanum; upper lip beige. (35) Dorsal parts of limbs: dorsal part of forelimbs, of thigh, of shank and of foot light brown with dark brown crossbands; posterior part of thigh light brown with darker region near vent and fine brown spots. (36) Ventral parts of head, body and limbs: throat dirty white with isolated dark melanophores; margin of throat brown with white spots; chest and belly white with brown sides; thigh brown with some white spots; macroglands white; webbing brown.

Male secondary sexual characters: (38) Vocal sacs present; indistinct on throat; paired, slit-like openings posterior on the floor of the mouth.

Variation. In most of the specimens, the dorsal pattern formed by small dark round spots regularly distributed on back is much more distinct than in the holophoront. The larger sized males and the females exhibit spiny warts which are very dense on head and limbs. Female sexual characters: Large creamy white ova visible through skin. Lateroventral glandular ridges are distinct in most specimens formed of individual glands. Femoral, axillary and suprabrachial glands are relatively small in most individuals but distinct. The femoral glands are a little larger in females than in males.

Comparison. L. nyx shows usually numerous regularly arranged small dark spots on dorsum, whereas the other species either show relatively uniform dorsal coloration ( L. eos , L. minimus ) or various larger sized spots forming triangular or W-shaped patterns. Its white throat, chest and belly distinguish it from L. lateralis , L. nahangensis , L. oshanensis , L. pluvialis , L. aereus , L. tuberosus and L. ventripunctatus . The webbing in L. nyx is less developed than in L. eos and L. pelodytoides but more than in L. aereus , L. alpinus , L. bourreti , L. lateralis , L. liui , L. pluvialis , L. sungi and L. ventripunctatus . The absence of fringes on toes distinguish this species from L. aereus , L. alpinus , L. bourreti , L. eos , L. fuliginosus , L. khasiorum , L. lateralis , L. liui , L. minimus , L. pelodytoides , L. sungi and L. tamdil . With a SVL of 26–30 mm in adult males and 36–42 mm in adult females, L. nyx is among the moderat-sized species of Lalos . L. sungi (males SVL 48–53 mm; females 57–59 mm) is the only known larger species. In L. bourreti males might reach SVL over 33 mm and females 42–45 mm, whereas in L. eos males (33–35 mm) are larger than known for L. nyx but female size (41 mm) is quite similar. L. pluvialis males are smaller (22– 23 mm) than known for L. nyx . The minimum size of L. alpinus (24–26 mm), L. khasiorum (25–27 mm), L. liui (23–27 mm) and L. ventripunctatus (24–28 mm) is below the minimum size of L. nyx .

Distribution. Known only from onymotope ( Fig. 9 ).

Natural history. Specimens of L. nyx were collected in April and May along forest streams (up to 5 m wide), in riparian forest floor up to 1.5 m distance from the water. Males were calling in and near the streams. The species ranges from 800 to 1700 m ( Bain & Nguyen 2004).

Etymology. From the Greek νύξ, nux, night. Transcribed as nyx . In Greek mythology Nyx was the primordial goddess of the night, a shadowy figure. The name refers to the nocturnal activity of Leptolalax species. Nomen used as a noun in apposition to the generic substantive.

Placement in molecular phylogeny. Leptolalax nyx is part of a clade that also includes with high support L. minimus , L. aereus , L. ventripunctatus and L. pluvialis . The specimen allocated to L. nyx is recovered with poor support as the sister taxon of the clade that includes L. minimus , L. aereus and L. ventripunctatus .

Conservation status. A large series of this species has been collected from the onymotope ( Bain & Nguyen 2004). According to these authors, the species was locally very abundant, but was observed in forest only. As there are no data on the extent of occurence, we propose the status Data Deficient for L. nyx .

Figures

FIGURE 4. Combined 16SrRNA Bayesian phylogeny and haplotype networks of 113 Leptolalax specimens with hierarchical outgroups (schematic representation in the grey box) The tree topology corresponds to the Bayesian topology obtained with three million generations, values on nodes indicate posterior probabilities (asterisks> 95 %, double asterisks> 99 %), and Maximum Likelihood bootstrap support values (> 70 %). Red numbers are the percentage of uncorrected p - sequence divergence between selected sister clades. Minimum spanning haplotype networks for two Leptolalax-clades (connected to phylogenetic tree nodes marked grey) were obtained with TCS. Numbers on haplotype connections represent number of nucleotide substitutions. Numbers of specimens included in haplotype networks are: B5-1(12); B5-2(17); B5-3(6); B5-4(1); B4-1(8); B4- 2,3,4,7,8(1); B4-5(2); B4-6(3). Sampling localities are provided as pie charts within haplotype circles, circle size corresponds to the number of sampled individuals. Abbreviations for country of origin are as follows: L—Laos, M—Malaysia, T—Thailand, V—Vietnam. Newly described species and haplotype networks are coloured.

FIGURE 9. Distribution of localities of specimens of subgenus Lalos studied in this work. Onymotopes are indicted as stars. Olive green—pelodytoides; blue—L. minimus form 2; orange yellow—L. minimus; red—L. aereus; grey—L. eos; light green – L. ventripunctatus; white—L. bourreti; black—L. pluvialis; yellow—L. nyx.

FIGURE 19. Leptolalax nyx, AMNH A163810, holophoront, adult male, SVL 26.9 mm. (A) Dorsal and (B) ventral view.

FIGURE 20. Leptolalax nyx, AMNH A163810, holophoront, adult male. (A) Lateral view of head, ventral view of (B) right hand and of (C) right foot. Scale bar = 5 mm (3 + 2 mm).