Raorchestes annandalii ( Boulenger, 1906 )

Boruah, Bitupan, Deepak, V. & Das, Abhijit, 2025, Revision of bush frogs, Raorchestes and Philautus (Amphibia: Anura: Rhacophoridae) from the northeast Indian biodiversity hotspot with description of thirteen new species, Vertebrate Zoology 75, pp. 517-625 : 517-625

Raorchestes annandalii ( Boulenger, 1906)

Figures 45 , 46; Tables 1, 2, S 12

Chresonymy.

Ixalus annandalii Boulenger, 1906: 385 .

Ixalus annandalei — Annandale (1908): 305; incorrect spelling.

Rhacophorus ( Philautus) annandalii — Ahl (1931): 71.

Philautus annandalii — Bourret (1942): 451; Gorham (1974): 166; Sarkar et al. (1992): 90; Dutta (1997): 74; Ahmed et al. (2009): 15, 147.

Philautus ( Philautus) annandalii — Bossuyt and Dubois (2001): 38.

Pseudophilautus annandalii — Li et al. (2009): 519.

Raorchestes annandalii — Subba et al. (2017): 4, 11; Frost (2025).

Comments on taxonomic status.

Boulenger (1906) described Raorchestes annandalii from Kurseong, Darjeeling (= Darjiling), West Bengal, India. Bossuyt and Dubois (2001) redescribed the lectotype ( BMNH 1947.2. 26.58; female). We re-examined the lectotype at NHM, London and we collected topotypes from Darjeeling. We found the following exception in our collected specimens against the lectotype description by Bossuyt and Dubois (2001): 1) head longer than wide (vs. head length equal to width), snout length equal to eye length (vs. snout length greater than or equal to eye length); tibia longer than thigh (vs. tibia shorter than or equal to thigh). Based on new information, we provide a revised diagnosis and expanded description of this species.

Material examined.

Lectotype ( BMNH 1947.2 . 26.58; Fig. 45 ) collected by N. Annandale from Kurseong , Darjeeling (= Darjiling), West Bengal .

Newly collected material.

Four adult males ( WII-ADA 521 , WII-ADA 537 , WII-ADA 548 , WII-ADA 551 ) and three adult females ( WII-ADA 520 , WII-ADA 530 and WII-ADA 533 ) collected by NGP on 23 April 2018 from Ravangla ( 27.2879°N, 88.34717°E, elevation 1780 m a. s. l.), Namchi District, Sikkim ; one adult male ( WII-ADA 2721 ) and two adult females ( WII-ADA 2716 and WII-ADA 2722 ) collected by NGP on 8 August 2022 near Rock Garden waterfall ( 27.02778°N, 88.22889°E, elevation 1500 m a. s. l.), Darjeeling District, West Bengal .

Diagnosis.

A small sized Raorchestes (Fig. 46 ), SVL 17.3–19.6 mm in adult males and SVL 18.9–21.6 mm in adult females; head length equal to head length; vomerine teeth absent; snout rounded to sub ovoid in dorsal view; snout slightly longer than eye length or equal to eye length ( EL / SL = 0.82–1.03); snout length greater than or equal to inter-upper eyelid width ( SL / IUE = 0.97–1.23); snout length greater than or equal to eye length ( SL / EL = 0.96–1.15); nostrils equidistant between eye and snout tip or closer to eye than snout tip; nuptial pad present on first finger in males; dorsal skin on head and dorsum smooth or shagreened; scattered tubercles towards dorsum and flank; dark brown band on inter-upper eyelid space; a pair of concave dark brown stripes on dorsum; brown mottling and white flecks on ventrum.

Description of a newly collected material ( WII-ADA 2721 ).

An adult male, small size, SVL 17.3 mm; head as long as wide ( HL / HW = 0.98); snout rounded in dorsal view, protruding beyond lower jaw in lateral and ventral views; snout length slightly greater than eye length ( EL / SL = 0.92); canthus rostralis rounded, oblique; loreal concave; narial region protruding; internarial distance slightly less than inter upper eyelid width ( IN / IUE = 0.91) and greater than upper eyelid width ( UEW / IN = 0.75); inter-upper eyelid space slightly convex; nostril oval, laterally positioned and obliquely oriented, equidistant between eye and snout tip; eye in moderate size, less than half of head length ( EL / HL = 0.4), slightly greater than inter upper eyelid width ( IUE / EL = 0.92); tympanum barely visible, rounded, one fourth of eye length ( HTYD / EL = 0.25); supratympanic fold distinct; vomerine teeth absent; choanae round; tongue posteriorly wide and medially notched, posterior two lobes widely separated; pair of internal vocal sac opening on lower jaw; habitus dorso-ventrally flattened, length more than half of snout-vent length ( AG / SVL = 0.52).

Forelimbs slender; hand longer than forearm ( FAL / HAL = 0.83); relative length fingers = I <II <IV <III; fingers with rounded disc; disc on third finger slightly wider than tympanic diameter ( HTYD /FIIID = 0.75); circum-marginal groove present on each disc; subarticular tubercles distinct and rounded except the proximal subarticular tubercles on third and fourth finger which small and indistinct; palmar tubercles indistinct; webbing on fingers absent; a fine granular nuptial pad on first finger.

Hindlimbs slender; thigh longer than tibia ( TBL / TL = 0.94) and less than half of snout-vent length ( TL / SVL = 0.48); relative length toes = I <II <III <V <IV; rounded disc on toe; disc width equal to that of fingers; subarticular tubercles distinct, rounded except the lower subarticular tubercles on toe III – V which are small and indistinct; indistinct inner metatarsal tubercle present and outer one absent; webbing slight, reaching second subarticular tubercle on fourth toe.

Snout and dorsal aspect of head smooth; an indistinct longitudinal ridge on middle of head; lateral aspect of head smooth, a tubercle present on mandibular region; dorsum smooth; flank granular towards ventrolateral aspect, indistinct; forelimbs and hindlimbs smooth on top; on ventrum, throat smooth; posteriorly gular skin granular; chest, and abdomen granular; granules on ventral aspect of thigh indistinct; tibia smooth on ventral aspect.

Colouration in life.

Head, dorsum and limbs brown on dorsal aspect; anterior part of head to interorbital space slightly paler than posterior part of head and dorsum; loreal region slightly darker; indistinct dark brown patch ventral to eye; a dark-brown stripe below the supratympanic fold; dark brown concave bar on inter-upper eyelid space and dark brown patch posterior to it; pair of concave dark brown stripes on dorsum, starting behind upper eyelid and posterior ends directing towards groin; a broad dark brown crossbar on forearm; similar band on each thigh, tibia, and tarsus; disc on finger and toe yellow; groin, lateral aspect of thigh, inner lateral side of tibia and tarsus reddish-brown; dark brown patch around vent; brown marbling and irregular white flecks on ventral side of head, abdomen and limbs.

Sexual dimorphism and morphological variation.

Males have a pair of internal vocal sac openings on lower jaw; external subgular vocal sac, and nuptial pad on first finger. Dorsal concave stripes and cross bars may be indistinct in some individuals of this species; tubercle towards flank may be completely absent; Detailed morphometric variations are given in Table S 12.

Morphological comparison.

Raorchestes annandalii differ from R. andersoni , R. dulongensis , R. hillisi , R. huanglianshan , R. menglaensis , and R. tytthus nov. comb. by position of nostril equidistant between eye and snout tip or closer to eye than snout tip (vs. nostril closer to snout tip than eye); it differs from R. cinerascens nov. comb. by snout length being greater than or equal to eye length (vs. snout length smaller than eye length); it differs from R. dulongensis by nostril being equidistant between eye and snout tip or closer to eye than snout tip (vs. nostril closer to snout tip than eye); it differs from R. hekouensis by presence of nuptial pad only on first finger (vs. nuptial pad present on first and second fingers); it differs from R. hillisi and R. huanglianshan by nostril being equidistant between eye and snout tip or closer to eye than snout tip (vs. nostril closer to snout tip than eye); it differs from R. jadoh by larger body size in adult males, SVL 17.3–19.6 mm (vs. 13.6–14.0 mm); it further differs from R. jadoh and R. jakoid by head length being greater than or equal to head width (vs. head wider than long), and thigh length being greater than or equal to tibia length (vs. thigh length less than tibia length); it differs from R. leiktho by larger body size in adult males, SVL 17.3–19.6 mm (vs. SVL 15.7–15.8 mm); it differs from R. longchuanensis by inter upper eyelid width being less than or equal to eye length (vs. inter-upper eyelid width greater than eye length); it differs from R. malipoensis by absence of black patches on groin and inner lateral aspect of thigh (vs. black patches present on groin and inner lateral side of thigh); it differs R. menglaensis by nostril being equidistant between eye and snout tip or closer to eye than snout tip (vs. nostril closer to snout tip than eye); it differs from R. mindat by the absence of black or white patches on groin (vs. enlarged black and white patches present on groin), by absence of white patches on the lateral side of thigh (vs. enlarged white patches on the lateral side of thigh); it differs from R. parvulus absence of dark brown and whitish blotch on groin (vs. dark brown marbling enclosing a whitish blotch present on groin); it differs from R. rezakhani by absence of dark or light pattern on the groin (vs. a short brown streak present on groin), and by snout length being greater than inter-upper eyelid width (vs. snout length less than or equal to inter upper eyelid width); it differs from R. tytthus nov. comb. by position nostril equidistant between eye and snout tip or closer to eye than snout tip (vs. nostrils closer to snout tip than eye); it differs from R. yadongensis by inter-upper eyelid width being less than or equal to eye length (vs. inter-upper eyelid width greater than eye length). Morphological comparisons of R. annandalii with newly described species in this study are provided in the morphological comparison section of each respective species and Table 1.

Phylogenetic relationship and genetic divergence.

Phylogenetically R. annandalii recovered as basal lineage to three species including R. arunachalensis sp. nov., R. magnus sp. nov. and R. longchuanensis in ML analysis with weak support (Fig. 2 ). In BI analysis, it is sister to R. mindat with weak support (Fig. 3 ). The genetic divergence with its congeners included in this study are 3.8–8.2 % in the 16 S, 13.7–19.7 % in the cyt b and 10.0–16.8 % in the COI genes (Table S 7 A – C).

Distribution and natural history.

Sarkar et al. (1992) reported this species from Kalimpong, Goomti, Mahanadi, Ghum Bhanjan in Northern West Bengal; Subba et al. (2017) reported it from Sikkim; Srestha (2001), Anders (2002), Khatiwada et al. (2021) and Shah and Tiwari (2004) reported it from Nepal. Calling aggregations were observed on shrubs after the dusk during April – July (Fig. 44 B ).

Remarks.

Annandale (1912) reported this species from Mangaldai, Assam; Chanda (1992, 1994) reported this species from Goalpara in Assam and Namdapha in Arunachal Pradesh followed by Sarkar and Ray (2006). Ao et al. (2003) reported this species from Nagaland. However, our sampling across the region shows that R. annandalii is restricted to Sikkim (Ravangla), Darjeeling (Rock Garden Waterfall) and eastern Nepal. Furthermore, the present study suggests that the previous records of this species from Assam ( Annandale 1912), Nagaland ( Ao et al. 2003) and Arunachal Pradesh ( Sarkar and Ray 2006; Mathew and Sen 2010) are erroneous. Wangyal et al. (2020) reported this species from Bhutan, which requires further verification to confirm the identity of this species.

Figures

Figure 2. A, B Maximum likelihood tree inferred from the concatenated data set (16 S, cyt b, COI and RHO) for Raorchestes species from northeast India, Indo-Burma and Indo-China. Outgroups are not shown in this tree. Numbers at the internal branches represent ultrafast bootstrap values (UFB). Values below 50 are not shown. Scale bar: substitutions per site.

Figure 3. A, B Bayesian tree inferred from the concatenated data set (16 S, cyt b, COI and RHO) for Raorchestes species from northeast India, Indo-Burma and Indochina. Outgroups are not shown in the tree. Numbers at the nodes represent posterior probability (PP) value. Values <0.5 are not shown. Scale bar: substitutions per site.

Figure 44. Habitats of Raorchestes mindat and R. annandalii A Landscape view of the hills at Fakim WLS and B landscape view at Darjeeling.

Figure 45. Raorchestes annandalii (lectotype; BMNH 1947.2. 26.58). A Dorsal and B ventral view, C ventral aspect of hand, D ventral aspect of foot, E granular skin on abdomen. scale bar = 10 mm.

Figure 46. Newly collected material of R. annandalii. A Dorsolateral and B ventral view of topotype (WII-ADA 2721) in life (inset image showing granular skin on abdomen). C WII-ADA 534 in life. D – G WII-ADA 520, D dorsal view immediately after euthanization (inset image showing fine granular skin on dorsum), E dorsal view, F lateral view of head, G ventral view. Scale bar = 10 mm. Photos A – D by Naitik G. Patel.