Gracixalus patkaiensis Boruah, Deepak, Patel, Jithin, Yomcha, and Das 2023

Tajo, Tage, Upadhyaya K., Radhakrishna, Dikshit Akalabya Sarmah, A. N., Garg, Sonali & Biju, S. D., 2025, Whistles in the reeds: a new country record of the deeply divergent Gracixalus medogensis, with additional insights on Gracixalus frogs (Rhacophoridae) in India, Zootaxa 5659 (4), pp. 511-535 : 529-531

Gracixalus patkaiensis Boruah, Deepak, Patel, Jithin, Yomcha, and Das 2023

( Figures 1–2 , 6 , 7 ; Tables 1–4 )

Remark. This species was recently described from a single locality in Namdapha National Park, Changlang district, Arunachal Pradesh, India by Boruah et al. (2023), where a detailed description can be found. Here, we report additional populations of this species, a morphological description, colour variations, and insights into natural history. Notably, we also document the presence of green blood and turquoise bones in this species making it the first report of such a characteristic in a species of frog from India.

Diagnosis. Distinguishable from its congeners by a combination of the following morphological characters: (1) relatively small male adult size, SVL 23.0– 26.5 mm; (2) body slender; (3) dorsum chartreuse green or yellowish-green with irregular light or dark brown spots; (4) snout mucronate in dorsal view, and vertical in lateral view; (5) canthus rostralis distinct and sharp; (6) head longer than wide (HL/HW 1.11–1.12); (7) snout longer than horizontal diameter of eye (SL/EL 1.25–1.27); (8) tympanum rather distinct; (9) dorsal and ventral skin is translucent, with skin of venter particularly immaculate, semi-transparent; (10) dorsal skin on snout, head, and upper eyelids granular with spinules of different size; (11) ventral skin granular; (12) moderately developed webbing on foot: fourth toe webbing up to the second subarticular tubercle on either side; (13) males with a smooth nuptial pad on finger I; (14) greenish bones clearly visible externally through the skin.

Adult morphology. Morphological description, based on three adult males. Small adult size ( SVL 23.0– 25.0) with a slender body; head longer than wide (HL/ HW 1.11 – 1.12 ); outline of the snout mucronate in dorsal view (pointed in original description), rounded in ventral view, and vertical in lateral view (obtuse in original description); canthus rostralis distinct and sharp; loreal region vertical and concave; interorbital region flat; snout longer than horizontal diameter of eye (SL/ EL 1.25 – 1.27 ); nostril nearer to the tip of snout than eye ( NS / EN 0.68– 0.71); internarial distance shorter than horizontal diameter of eye ( IN / EL 0.78–0.83); interorbital width greater than upper eyelid width ( IUE / UEW 1.35 – 1.38 ); tympanum rather distinct, diameter shorter than eye diameter ( TYD / EL 0.44–0.47); supratympanic fold distinct and extends up to the axilla.

Forelimbs relatively slender; relative length of fingers FLI <FLII <FLIV <FLIII; tips of all fingers with well-developed discs having horizontal circummarginal grooves, discs relatively wide compared to finger width; webbing absent between fingers; subarticular tubercles prominent, rounded, all present, palmar tubercles indistinct; nuptial pads present on posterolateral surface of finger I.

Hindlimbs relatively long; thigh nearly equal to shank (TL/ShL 0.98–1.01) and longer than foot (TL/FOL 1.26–1.30); shank longer than foot (ShL/FOL 1.28–1.29); relative length of toes TLI <TLII <TLIII <TLV <TLIV; tips of all toes with well-developed discs having distinct circum-marginal grooves; toes moderately webbed, webbing formula: I2 –– 2 + II2 –– 3 – III2 –– 3IV3 –– 2 – V; subarticular tubercles rounded, distinct; inner metatarsal tubercle oval; outer metatarsal tubercle and supernumerary tubercles absent; dermal ridge along the outer margin of tibia; and tarsal fold absent ( Figure 7 ).

Dorsal surfaces of head, body and limbs shagreened with scattered tubercles; more prominently granular skin on upper eyelids, supratympanic fold, and dorsolateral surfaces; supratympanic fold distinct, extending from eye to angle of jaw; throat and chest smooth, belly and ventral surface of thighs granular.

Colour variation in life. Dorsum including head and limbs chartreuse green or yellowish-green with irregular light or dark brown spots; discontinuous light brown cross bands on both fore and hindlimbs; eyelids dark brown; a relatively broad brown stripe extends from the tip of snout mid-way up to the lateral side of dorsum, while passing over canthus rostralis, narial opening, margins of upper eyelids and supratympanic fold; light green lateral surfaces of head lighter than dorsum; a white patch begins on the upper jaw below the level of mid-eye and extends posteriorly over the shoulder region or up to the groin; iris golden yellow with brown marbling; finger and toe tips yellowish-green, brown patches (formed by minute speckles) on anterior part of the webbing between fourth and fifth digits of the hindlimbs.

Skin and internal structures. Dorsal and ventral skin is translucent, with skin of venter particularly immaculate, semi-transparent (except for white patches on the chest and upper abdomen); turquoise bones (especially of limbs, but also the vertebral column, pelvic region, parts of the skull and outline of the lower jaw) and greenish bones clearly visible externally through the skin, both in life and preservation ( Figure 7 ); greenish blood also noted while excising portion of the thigh muscle for obtaining a tissue sample from the anesthetised animal before preservation.

Distribution. Apart from the holotype locality, Kamala Valley Beat (25 mile), the present study recorded Gracixalus patkaiensis from two additional localities—Gandhigram (27°27’22.59” N 96°38’11.21” E, elevation 627 m asl and 27°27’25.12” N 96°39’8.54” E, elevation 661 m asl) and Vijoynagar (27°12’35.1” N 96°57’28.9” E, elevation 1154 m asl), all in Changlang district, Arunachal Pradesh state, India. Based on these findings, this species likely has a wider distribution range within the Namdapha National Park, and perhaps also the adjoining regions of Myanmar, although locating this species during general surveys may be difficult due to its short breeding period. Even during the breeding period, locating individuals by their calls can be challenging, as their faint call whistles, akin to insect-like calls, are often masked by the background calls of invertebrates in the area, necessitating more dedicated searches. The elevation range of the surveyed areas was between 600 and 1200 m asl.

Natural history. The habitat of Gracixalus patkaiensis at its type locality, Kamala Valley Beat (25 mile), lies within evergreen forests with a closed canopy cover, dominated by tall trees with overhanging vines, rattan palm, and scattered bamboo clumps. Individuals were found perching on small shrubs and ferns near a stream that also served as a water source for a nearby forest camp. Only a solitary call was heard from this location in the month of August, perhaps because of less breeding activity or persistent heavy rainfall. In contrast, at Gandhigram and Vijoynagar, the vegetation was characterized by dense shrubs, primarily comprised of bamboo clumps, with sparse trees and an open canopy cover. Cardamom plantations were also observed nearby. Calling males were located on a reed patch adjacent to the road in Gandhigram during the month of August. Males were observed calling from heights ranging between 0.5–1.0 m above the ground. The calling activity began as early as 16:00 h and subsided by around 21:30 h.

Vocalisation. Vocal repertoire ( Figure 6 ; Table 4 ). The male calls of G. patkaiensis were recorded on 20 August 2024, around 21:00 h, from a bamboo patch in Gandhigram, Namdapha National Park , Changlang district , Arunachal Pradesh. Ambient air temperature at the time of recording was 23.5 °C (dry bulb) and 22 °C (wet bulb). We recorded and analysed 14 calls produced by a single individual that was found sitting on a bamboo leaf at a height of about 0.5 m above ground. The vocal repertoire consisted of two types of calls (type 1 and type 2) that were delivered in groups and without any particular order; but type 2 calls when present, always followed the type 1 calls. The whistle-like type 1 calls were non-stereotypical and highly variable, with a relatively longer call duration of 46.2 ms (range, 3.2−112.7 ms), a rise time of 24.1 ms (range, 1.1−78.4 ms), and a fall time of 22.2 ms (range, 9.9−42.6 ms). The spectrum showed harmonics and had a mean dominant frequency of 4.21 ± 0.33 kHz (3.53−4.57 kHz). The type 2 calls were relatively constant and had a shorter call duration of 4.6 ms (range, 3.2−5.8 ms). They had a mean rise time of 1.4 ms (range, 1.1−1.7 ms) and a mean fall time of 3.2 ms (range, 1.9−4.1 ms). The overall dominant frequency was 4.1 ± 0.16 kHz (range, 3.92−4.22 kHz).

Call comparison. We compared the calls of G. patkaiensis from the current study with the calls of another population of this species reported by Boruah et al. (2023). The type 1 calls in our study that are comparable to the ‘whistles’ were highly variable, whereas the type 2 calls that are comparable to the ‘clicks’ were broadly similar. The call duration of type 1 calls (13.2−112.7 ms vs. 45–229 ms) and their dominant frequency (3.53−4.57 kHz vs. 4.35−4.61 kHz) fell within broad ranges in both the populations. Likewise, the call duration of type 2 calls (3.2−5.8 ms vs. 7.0–65.0 ms) and their dominant frequency (3.92−4.22 kHz vs. 3.10 −4.61 kHz) were also similar.

Figures

FIGURE 1. Map of the Northeast region of India and neighbouring countries showing the genetically verified distribution of Gracixalus medogensis (China: blue circle; India: light and dark green circles) and G. patkaiensis (red, orange, and pink circles). The type localities are indicated with an asterisk (*) symbol inside the circles. Administrative boundaries are based on maps published by the Survey of India (www.surveyofindia.gov.in).

FIGURE 2. Maximum Likelihood phylogram for the genus Gracixalus sensu lato, based on mitochondrial 16S rRNA, showing the phylogenetic position of the new populations (in bold face) of G. medogensis and G. patkaiensis from Arunachal Pradesh, India. Values on the branches indicate Ultrafast Bootstrap Support (UBS>50%) and Bayesian Posterior Probabilities (BPP>50%), respectively. Voucher details in the taxon labels are referenced in Table 1. Type species of Gracixalus sensu stricto and Orixalus are indicated with asterisk symbols at the nodes.

FIGURE 6. Acoustic properties of a typical male advertisement call of Gracixalus medogensis and G. patkaiensis from Arunachal Pradesh, India. A–F. G. medogensis: A. Oscillogram for 30 s call segment; B. oscillogram for 10 s call segment; C. oscillogram for 1.0 s call segment; D. spectrogram for 1.0 s call segment; E. oscillogram for 0.3 s call segment of type 1 call; F. oscillogram for 0.1 s call segment of type 2 call; G–I. G. patkaiensis: G. oscillogram for 1.0 s call segment; H. spectrogram for 1.0 s call segment; I. oscillogram for 0.1 s call segment.

FIGURE 7. External morphology and internal structures visible through skin in Gracixalus patkaiensis from Gandhigram, Arunachal Pradesh, India, in life (except D, E, five days after preservation). A–E. SDBDU 2024.6709 (male): A. dorsolateral view; B. dorsal view; C. ventral view; D. dorsal view; E. ventral view; F–N. SDBDU 2024.6708 (male): F. dorsal view; G. ventral view; H. frontal view; I. ventral view showing turquoise bones; J. dorsal view of hand; K. dorsal view of foot; L. ventral view of foot; M. posterior view of thighs; N. dorsal view of thighs. Photographs: S. D. Biju.