Nyctibatrachus webilla, Sonali Garg, Robin Suyesh, Sandeep Sukesan & Sd Biju, 2017

Sonali Garg, Robin Suyesh, Sandeep Sukesan & Sd Biju, 2017, Seven new species of Night Frogs (Anura, Nyctibatrachidae) from the Western Ghats Biodiversity Hotspot of India, with remarkably high diversity of diminutive forms, PeerJ 5 (3007), pp. 1-50 : 35-39

Nyctibatrachus webilla sp. nov.

urn:lsid:zoobank.org:act:735BCF83-6BE0-4F2A-97E6-39BFCDA5B944

Kadalar Night Frog

( Figs. 1 , 9–11 ; Tables S1–S8)

Holotype. ZSI/WGRC/V/A/933, adult male, from Kadalar (10°0 7 52.0 N 77°0 0 0 1.8 E, 1429 m), Idukki district, Kerala state, India, collected by SDB and SG on 0 8 June 2016. Paratypes. ZSI/WGRC/V/A/934, adult male, collected along with the holotype, and ZSI/WGRC/V/A/935–936, two adult males, collected from the same locality as holotype, by SDB and SG on 18 August 2013.

Etymology. The species name is derived from the English term ‘web’ between toes and the Malayalam word ‘illa’, meaning ‘no’—referring to the prominently reduced foot webbing in this species in comparison to its close relative Nyctibatrachus deccanensis . The species name is treated as an invariable noun in apposition to the generic name.

Diagnosis. Nyctibatrachus webilla can be distinguished from known congeners by the following combination of morphological characters: (1) small male adult size (SVL 18.7– 20.7 mm, N = 4); (2) head wider than long (male HW/HL ratio 110.8–117.4%, N = 4); (3) glandular ridges on sides of the head, anterior and posterior parts of back, upper and lower parts of flank, and a glandular ridge between the eyes; (4) third finger disc slightly wider than finger width (male FDIII 0.3–0.4, FWIII 0.2–0.3, N = 4), without groove; (5) fourth toe disc moderately wider than toe width (male TDIV 0.6–0.7, TWIV 0.3–0.4, N = 4), with dorso-terminal groove and cover bifurcate distally; (6) presence of two palmar tubercles; (7) foot webbing basal, fourth toe webbing just above the third subarticular tubercle on either side; (8) thigh longer than shank (male TL/SHL ratio 106.9–111.1%, N = 4); (9) shank shorter than foot length (male SHL/FOL ratio 90.0–93.5%, N = 4); and (10) bright reddish-orange ventral coloration in life.

Morphological comparison. Nyctibatrachus webilla can be distinguished from its congeners N. acanthodermis , N. danieli , N. dattatreyaensis , N. gavi , N. grandis , N.

humayuni , N. indraneili , N. jog , N. karnatakaensis , N. kumbara , N. major , N. periyar ,

N. petraeus , N. poocha , N. radcliffei sp. nov., N. sanctipalustris , N. sylvaticus and N. vrijeuni by its smaller adult male snout-vent size, SVL 18.7–20.7 mm (vs. larger, male SVL 24.2– 76.9 mm), and dorsal skin less prominently wrinkled and/or granular (vs. prominently wrinkled and/or granular); differs from N. anamallaiensis , N. beddomii , N. manalari sp. nov., N. minimus , N. pulivijayani sp. nov., N. robinmoorei sp. nov. and N. sabarimalai sp. nov. by its larger adult male snout-vent size, SVL 18.7–20.7 mm (vs. smaller, male SVL 10–18 mm); differs from N. aliciae , N. deveni , N. pillaii , N. shiradi and N. vasanthi by its third finger disc without groove (vs. third finger disc with dorso-terminal groove and cover notched distally in N. aliciae , N. deveni and N. shiradi ; third finger disc with dorso-terminal groove and cover bifurcate distally in N. pillaii and N. vasanthi ), and webbing between toes reduced, specifically fourth toe webbing just above the third subarticular tubercle (vs. medium webbing between toes, specifically fourth toe webbing extending well beyond the second subarticular tubercle on either side).

Because of the comparable snout-vent size, Nyctibatrachus webilla could be confused with previously known species N. deccanensis , N. kempholeyensis and N. minor , and the new species N. athirappillyensis sp. nov. However, N. webilla differs from N. deccanensis by its snout rounded in ventral view (vs. semi-circular), relatively larger male SL/HL ratio of 46.2– 49.3%, N = 4 (vs. male SL/HL ratio of 30–38.7%, N = 15), relatively larger male EL/HL ratio of 34.4–36.2%, N = 4 (vs. male EL/HL ratio of 25.4–30.9%, N = 15), and reduced foot webbing, especially fourth toe webbing just above the third subarticular tubercle on either side, I2−–2−II2−–3III3−–4−IV4−–3−V (vs. up to the second subarticular tubercle Garg et al. (2017), PeerJ, DOI 10.7717/peerj.3007 37/50 on either side, I1 3/4–2−II2−–3−III2–3IV3–2V). Since N. webilla is found in a region that is geographically close to the type locality of N. sholai , a nomen currently in the synonymy of N. deccanensis ( Biju et al., 2011) , we also compared the new species with the holotype of N. sholai . A comparison of relative degree of foot webbing in the holotype of N. sholai (= N. deccanensis ), lectotype of Rana pygmaea (= Nyctibatrachus deccanensis ) and the holotype of N. webilla are shown in Fig. 10 .

Nyctibatrachus webilla differs from N. kempholeyensis by its third finger disc without groove (vs. with dorso-terminal groove and cover rounded distally), fourth toe disc with dorso-terminal groove and cover bifurcate distally (vs. with dorso-terminal groove and cover notched distally), reduced foot webbing, especially the fourth toe webbing just above the third subarticular tubercle on either side, I2−–2−II2−–3III3−–4−IV4−–3−V (vs. well beyond the second subarticular tubercle on either side, I1–2−II1–2 1/4III1–2 1/2IV2 1/2–1V), and bright reddish-orange ventral coloration in life (vs. flesh or off white).

Nyctibatrachus webilla differs from N. minor by its relatively larger snout-vent size, male SVL 18.7–20.7 mm, N = 4 (vs. male SVL 15.4–17.9 mm, N = 6), third finger disc without groove (vs. with dorso-terminal groove and cover bifurcate distally), and bright reddish-orange ventral coloration in life (vs. flesh or off white).

Nyctibatrachus webilla differs from N. athirappillyensis by its third finger disc without groove (vs. with dorso-terminal groove and cover rounded distally), fourth toe disc with dorso-terminal groove and cover bifurcate distally (vs. with dorso-terminal groove and cover notched distally), reduced foot webbing, specifically the fourth toe webbing just above the third subarticular tubercle on either side, I2−–2−II2−–3III3−–4−IV4−–3−V (vs. well beyond the second subarticular tubercle on either side, I1–1 3/4II1–2+III1–2+IV2+–1V), and bright reddish-orange ventral coloration in life (vs. flesh or off white). For more differences with N. athirappillyensis , see comparison of that species.

Description of holotype (measurements in mm). Adult female (SVL 20.7); head small, wider than long (HW 8.1, HL 6.9); snout rounded in dorsal and lateral views, its length (SL 3.2) longer than horizontal diameter of eye (EL 2.5); loreal region acute and concave with indistinct canthus rostralis; interorbital space flat, wider (IUE 3.0) than upper eyelid (UEW 1.1) and internarial distance (IN 2.2); nostril closer to eye (EN 1.3) than the tip of snout (NS 1.9); tympanum indistinct; vomerine ridge present, bearing small teeth, at an angle of 45° to the body axis, closer to each other than choanae, longer than the distance between them; tongue moderately large, emarginated, bearing no median lingual process. Forearm (FAL 3.4) shorter than hand length (HAL 4.9), finger length formula: I <II <IV <III, finger discs slightly wider compared to finger width (FDI 0.4, FWI 0.3; FDII 0.4, FWII 0.3; FDIII 0.4, FWIII 0.3; FDIV 0.4, FWIV 0.3), finger discs rounded without grooves; dermal fringe present; subarticular tubercles prominent, oval, single, all present; prepollex distinct, oval; two palmar tubercles, oval, distinct; nuptial pads present. Thigh length (TL 9.9) longer than shank (SHL 9.0) and nearly equal to foot (FOL 9.8), toe discs moderately wider compared to toe width (TDI 0.7, TWI 0.4; TDII 0.7, TWII 0.4; TDIII 0.8, TWIII 0.5; TDIV 0.6, TWIV 0.4; TDV 0.6, TWV 0.4), toe disc with dorso-terminal groove, cover bifurcate distally; foot webbing basal: I2−–2−II2−–3III3−–4−IV4−–3−V; subarticular tubercles well developed, oval; a long and slender inner metatarsal tubercle; outer tubercle absent; tarsal fold extending from anterior edge of inner metatarsal tubercle; dermal fringe from tip of toe to heel along toe V well developed.

Skin of snout shagreened to granular, upper eyelids with a few glandular warts; sides of the head, anterior and posterior parts of back, and upper and lower parts of flank with glandular ridges; a glandular ridge between the eyes; subocular gland weakly developed, extending from the posterior ventral border of the orbit towards the posterior axis of the mandibles; supratympanic fold distinct, extending from posterior corner of upper eyelid to near the shoulder; upper surface of arms and legs with weakly developed granular projections; ventral surfaces smooth.

Colour of holotype. In life. Dorsum and lateral sides of head bright reddish-orange with scattered minute black spots, upper eyelids dark brown ( Figs. 11 A and 11C); forelimbs (including fingers) and hind limbs (including toes) dark reddish-brown with dark brown transverse bands; anterior and posterior parts of flanks orange. Ventral surfaces reddishorange, hand and foot greyish-brown ( Fig. 11 F). In preservation. Dorsum and lateral sides of head light grey with scattered minute black spots and dark grey glandular folds, upper eyelids dark grey ( Fig. 11 I); forelimbs (including fingers) and hind limbs (including toes) grey with dark grey transverse bands; anterior and posterior parts of flanks light grey. Ventral surfaces greyish-white, margins of forelimbs and hind limbs darker grey. Variations. Morphometric data from four adult males, including the holotype, is given in Table S6. Overall, the colour, markings and meristic characters of the paratypes are similar to the holotype.

Secondary sexual characters. Male (ZSI/WGRC/V/A/933), femoral glands present ( Figs. 11 G and 11H), nuptial pads weakly developed.

Vocalization. Male (ZSI/WGRC/V/A/935) of Nyctibatrachus webilla produced a single type of call with a pulsatile temporal structure. Calls were not delivered in groups and had uniform intervals. A typical advertisement call had a duration of 201.5 ms with 20 pulses delivered at a rate of 104 pulses/s, rise time of 52.9 ms, fall time of 92.5 ms, and the overall dominant frequency of 3.4 kHz with two broad peaks (Table S8; Figs. 9 E–9H).

Distribution and natural history. Nyctibatrachus webilla is currently known only from its type locality, which is located south of Palghat gap in the Western Ghats state of Kerala. Animals were found hidden either under leaf litter or vegetation on marshy ground close to a shallow rivulet. The specific collection site was located inside a disturbed forest patch adjacent to tea estate. Males were collected and observed calling both during the day (around 10:00–12:00 h) and night (between 19:00–22:00 h).

Figures

Figure 1 Morphometric differentiation of species using the discriminant function analyses. (A) Projection on factor plane first and second explaining 79.1 % of the variations among seven miniature-sized species. (B) Projection on factor plane first and second explaining 83.9 % of the variations among five medium-sized species. (C) Projection on factor plane first and second explaining 86.3 % of the variations among six large-sized species.

Figure 9 Male advertisement calls of Nyctibatrachus sabarimalai sp. nov. and Nyctibatrachus webilla sp. nov. (A – D) Nyctibatrachus sabarimalai sp. nov. (A) 10 s segment. (B) 1 s segment showing a single pulsatile call. (C) 0.1 s segment. (D) Spectrogram of 1 s call segment. (E – H) Nyctibatrachus webilla sp. nov. (E) 10 s segment. (F) 1 s segment showing a single pulsatile call. (G) 0.1 s segment. (H) Spectrogram of 1 s call segment.

Figure 10 Relative degree of foot webbing in the Lectotype (NHM 1947.2.4.51) of Nyctibatrachus deccanensis (A), Holotype (ZSI / WGFRS / V / A 611) of Nyctibatrachus sholai (= Nyctibatrachus deccanensis) (B), and Holotype (ZSI / WGRC / V / A / 933) of Nyctibatrachus webilla sp. nov. (C). Ventral surface of foot is shown on the left and schematic illustration on the right.

Figure 11 Holotype of Nyctibatrachus webilla sp. nov. (ZSI / WGRC / V / A / 933). (A) Dorsolateral view, in life. (B) Size (SVL 20.7 mm) in comparison to the Indian five-rupee coin (24 mm diameter). (C) Dorsal view, in life. (D) Dorsal surface of third finger disc, in preservation. (E) Dorsal surface of fourth toe disc, in preservation. (F) Ventral view, in life. (G) Femoral glands, in preservation. (H) Close-up of femoral glands after removal of skin showing multiple glands. (I) Lateral view of head, in preservation. (J) Ventral view of hand, in preservation. (K) Ventral view of foot, in preservation. (L) Schematic illustration of foot webbing.