Raorchestes leiktho, Köhler & Dost & Than & Ohler & Charunrochana & Chuaynkern & Chuaynkern & Geiss, 2025

Köhler, Gunther, Dost, Ole, Than, Ni Lar, Ohler, Annemarie, Charunrochana, Panupong Thammachoti, Chuaynkern, Yodchaiy, Chuaynkern, Chantip & Geiss, Katharina, 2025, A taxonomic revision of the genus Raorchestes in Myanmar and Thailand with the description of two new species from Myanmar (Amphibia, Anura, Rhacophoridae), Zootaxa 5613 (1), pp. 47-81 : 66-69

Raorchestes leiktho sp. nov.

urn:lsid:zoobank.org:act:FB6A2374-35D6-485B-850A-F2E592CDA7AB

Figs. 7 , 8B–D

Holotype. SMF 106234 , an adult male collected near Leiktho (19.20332, 96.58682; 875 m a.s.l.), Hp-an District, Kayin State, Myanmar, collected 25 June 2019 by Gunther Köhler and Ni Lar Than. Field tag number GK-7199.

Paratypes. Both from near Leiktho, Hp-an District , Kayin State, Myanmar, collected by Gunther Köhler and Ni Lar Than. SMF 106235 , same collecting data as holotype. SMF 106284 , 19.21164, 96.58678; 855 m a.s.l. Both paratypes are adult males.

Diagnosis and comparisons. A species of the genus Raorchestes (our former “ R. sp. 2”) that differs from geographically and molecularly relevant congeners of the Raorchestes parvulus group by the following combination of characters: (1) 15.72–15.80 mm SVL in males, n = 3; females unknown; (2) head about as wide as long (ratio HW/HL 0.92–1.10); (3) tympanum indistinct, supratympanic fold indistinct; (4) webbing between Toes 1 and 2 absent, between Toes 2 and 3 vestigial; webbing formula for Toes 3, 4 and 5: III 2–3½ IV 3 1/3–2 V; (5) tibiotarsal articulation reaching to level of mid-eye when hind limb is stretched alongside of body; (6) nuptial pad small and white; (7) inner metatarsal tubercle oval, outer metatarsal tubercle absent; (8) ridges or fringes along toes absent; (9) interorbital distance shorter than to subequal to eye horizontal diameter (ratio IOD/EYD 0.78–1.04); and (10) nostril closer to tip of snout than eye.

Raorchestes leiktho sp. nov. differs from its South-east Asian congeners by the following characteristics (condition for R. leiktho in parentheses): Lectotype of Ixalus parvulus Boulenger, 1893 (i.e., MSNG 29838): shorter hind legs, SHL/SVL 0.41 (vs. 0.51–0.54); and head longer than wide (vs. about as long as wide). R. cangyuanensis : larger male adult size, SVL of adult males mostly> 17 mm (vs. <17 mm); more toe webbing (vs. less toe webbing with webbing between Toes 1 and 2 absent, between Toes 2 and 3 vestigial); SL/HL mostly <0.45 (vs. mostly>0.45); TFOL mostly <0.68 (vs. mostly>0.68); dominant frequency of male advertisement call 2789–2906 Hz (vs. 3618–4134 Hz), note duration 0.021 – 0.035 s (vs. 0.014 – 0.027 s). R. gryllus : a distinct calcar tubercle and a series of whitish tubercles along lower arm as well as on foot and tarsus present (vs. these structures absent). R. huanglianshan : larger male adult size, SVL of adult males mostly> 17 mm (vs. <17 mm); shorter hind legs, TFOL mostly <0.68 (vs. mostly>0.68), SHL/SVL <0.48 (vs.>0.50); and all ventral surfaces heavily suffused with dark pigment (vs. pale). R. longchuanensis : larger male adult size, SVL of adult males mostly> 17 mm (vs. <17 mm); shorter hind legs, TFOL mostly <0.68 (vs. mostly>0.68), SHL/SVL <0.5 (vs.>0.5); SL/HL mostly <0.4 (vs.>0.4); male advertisement call a trill (vs. single notes) with a dominant frequency of 3381–3467 Hz (vs. 3618–4134 Hz). R. menglaensis : larger male adult size, SVL of adult males mostly> 17 mm (vs. <17 mm); SL/HL mostly <0.42 (vs.>0.42); dominant frequency of male advertisement call 4005–4479 Hz (vs. 3618–4134 Hz), note duration 0.031 – 0.076 s (vs. 0.014 – 0.027 s). Raorchestes hillisi : shorter hind legs, SHL/SVL <0.49 (vs.>0.50); shorter foot, FL/SVL <0.39 (vs.>0.39); longer head, HL/SVL>0.4 (vs. <0.4); UEW/HL <0.21 (vs.>0.21). Raorchestes malipoensis : shorter hind legs, TFOL <0.65 mm (vs.> 0.65 mm); IOD/HL>0.4 (vs. mostly <0.4). Raorchestes rezakhani : inner metatarsal tubercle absent or indistinct (vs. distinct); UEW/HL>0.28 (vs. <0.28); IOD/HL>0.45 (vs. <0.45); HNL/ SVL <0.25 (vs.>0.25); HW/HL about 1.5 (vs. about 1.0); male advertisement call a trill (vs. single notes) with a dominant frequency of 3469–3680 Hz (vs. 3618–4134 Hz). R. tytthus and R. dulongensis : conspicuous white blotches present in groin and on thigh (vs. such white blotches absent); and by having longer hind legs that reach to beyond anterior margin of eye when hind limb is stretched alongside of body (vs. to posterior border of eye). Raorchestes mindat : fingers and toes with lateral dermal ridges on both sides (vs. all fingers and toes without lateral dermal ridges); inner metatarsal tubercle rounded (vs. oval); more toe webbing with webbing between Toes 1 and 2 vestigial and web reaching to second phalanx on inner side of Toe 2 and to inbetween phalanges 3 and 4 on outer side of Toe 3 (vs. webbing between Toes 1 and 2 absent, between Toes 2 and 3 vestigial); shorter hind legs, THL/ SVL <0.45 (vs.>0.45), SHL/SVL <0.5 (vs.>0.5).

Description of the holotype ( Fig. 7 ). Adult male, as indicated by loose wrinkled skin of vocal sac in throat region and presence of vocal slits; SVL 15.79 mm; habitus robust; head broad, longer than wide, ratio HW/HL 0.92; snout nearly rounded in dorsal view, projecting beyond lower jaw, rounded in profile; nostril closer to tip of snout than eye; canthus rostralis rounded, loreal region slightly concave; eyes moderately large (EYD 2.82 mm) and protruding, pupil horizontal; ratio EYD/HL 0.5; IOD (2.20 mm) greater than width of upper eyelid (1.26 mm); tympanum indistinct; ratio TYD/EYD 0.25; vomerine teeth absent; tongue fleshy, rounded, without notch; supratympanic fold indistinct. Numerous minute pointed tubercles on upper eyelid and on dorsum. Forelimbs fairly robust (FHL 7.86 mm); relative finger lengths: I <II <IV <III, tips of all four fingers expanded into discs with circum-marginal grooves; discs of outer two fingers larger than those of Fingers I and II; all fingers without lateral dermal fringes or ridges; subarticular tubercles distinct, rounded; supernumerary tubercles absent; no webbing between fingers; inner (i.e., thenar) and outer (i.e., palmar) metacarpal tubercle oval, about subequal in size; nuptial pad small and white on dorsal surface of the first finger. Foot relatively robust (FL 6.58 mm), shorter than shank length (SHL 8.23 mm); relative toe lengths: I <II <III <V <IV; tips of toes with discs having circum-marginal grooves, toe discs smaller than finger discs; all toes without lateral dermal fringes or ridges; subarticular tubercles distinct, rounded; supernumerary tubercles absent; webbing between Toes 1 and 2 absent, between Toes 2 and 3 vestigial; webbing formula for Toes 3, 4 and 5: III 2–3½ IV 3 1/3–2 V; inner metatarsal tubercle round, outer metatarsal tubercle absent. Tibiotarsal articulation reaching to level of mideye when hind limb is stretched alongside of body.

Coloration after about four years preservation in 70% ethanol was recorded as follows: Dorsum Cinnamon-Drab (color 50), grading into Pale Buff (1) on flanks and with a Raw Umber (23) interorbital bar as well as a pair of anteriorly merging dorsolateral Raw Umber (23) stripes that have a triangular lateral extension in scapular region; a short oblique Brownish Olive (276) bar in groin; dorsal surfaces of thigh, shank and foot Pale Cinnamon (55) with Brownish Olive (276) transverse bars; upper eyelid Medium Plumbeous (294); a prominent Sepia (286) blotch on left side in flank region; all ventral surfaces Pale Buff (1).

Genomic characterization. Whole genome sequencing yielded 359,728,560 Illumina short reads with a total data size of 126.2 Gb. Genome assembly resulted in a highly fragmented and incomplete genome of 152 Mb in size. The assembly contains 225,418 contigs the largest contig being 862,400 bp and an N50 of 623 bp. The BUSCO analysis resulted in 86 recovered complete BUSCOs representing a completeness of 1.7 % (complete: 1.7% [single-copy: 1.2%, duplicates: 0.5%], fragmented: 0.3%, missing: 98.0%, n: 5310). The mitochondrial genome was assembled into one linear contig with a total length of 16,813 bp (Genbank accession No. PV077347). A total of 37 genes could be annotated, including all 13 protein coding genes, 2 rRNAs and 22 tRNAs. Pairwise alignment to the complete mitochondrial genome of Zhangixalus chenfui (GenBank accession No. NC_062878.1) revealed a pairwise identity of 78.78%. The raw genomic data for SMF 106234 can be accessed from the Sequence Read Archive (SRA) under SRR31929898.

Variation. The paratypes agree well with the holotype in general appearance, morphometrics (see Table 6 ), and coloration (see Fig. 8A–C ). However, in some paratypes the largest toe discs are smaller than the largest finger discs.

Etymology. The species name “ leiktho ”, a noun in apposition, refers to the village of Leiktho, Kayin State, Myanmar, where the type series of this species was collected.

Natural history notes. The type specimens of Raorchestes leiktho were collected at night (21:00–22:00 h) in small trees (<4 m height) adjacent to an agricultural area. The frogs were sitting on twigs in these trees about 100– 200 cm above ground level. The calls of numerous males were heard on the two days we spent at this locality.

Geographic distribution and conservation. Raorchestes leiktho is currently known only from its type locality in central-eastern Myanmar ( Fig. 9 ). At this point this species is only known from the three specimens that constitute the type series and we therefore classify it as Data Deficient according to the IUCN categories ( IUCN 2012).

Figures

FIGURE 7. Holotype of Raorchestes leiktho sp. nov. (SMF 106234). Scale bars equal 10.0 mm in A and B, 1.0 mm in C–H. Photos by G.K.

FIGURE 8. Individuals of Raorchestes in life. (A) female R. cangyuanensis, SMF 103268; (B) male paratype of Raorchestes leiktho sp. nov., SMF 106284; (C) male holotype of Raorchestes leiktho sp. nov., SMF 106234; (D) male paratype of Raorchestes leiktho sp. nov., SMF 106235; (E) male R. longchuanensis, SMF 10628; (F) female R. longchuanensis, SMF 107099; (G) male R. menglaensis, SMF 107104; (H) male R. menglaensis, SMF 107112. Photos by G.K. (A–E) and O.D. (F–H).

FIGURE 9. Map indicating collecting localities of the Raorchestes species occurring in South-east Asia. Each symbol can represent one or more adjacent localities.