Nyctibatrachus athirappillyensis, 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 : 9-14

Nyctibatrachus athirappillyensis sp. nov.

urn:lsid:zoobank.org:act:4756A24F-60E1-4B85-956F-5FC3CE6B876F

Athirappilly Night Frog

( Figs. 1–3 ; Tables S1–S8)

Holotype. ZSI/WGRC/V/A/891, adult male, from Thavalakuzhipara (10°16 53 N

76°41 25.6 E, 530 m), Vazhachal forest division, Thrissur district, Kerala state, India, collected by SDB and SG on 11 September 2015.

Paratypes. ZSI/WGRC/V/A/892–895, four adult males, and ZSI/WGRC/V/A/896, adult female, collected from the same locality as holotype, by SDB and SG on 11 July 2016. Etymology. The species epithet is an adjective that refers to Athirappilly falls, which is in close vicinity of the type locality.

Diagnosis. Nyctibatrachus athirappillyensis can be distinguished from known congeners by the following combination of morphological characters: (1) small male adult size (SVL 20.9–22.8 mm, N = 5); (2) head width nearly equal to head length (male HW/HL ratio 96.3–100%, N = 5); (3) a well developed ridge extending from the lip over the tip of the snout to between the nostrils, at which point it bifurcates, producing an inverted ‘Y’; (4) third finger disc slightly wider than finger width (male FDIII 0.5–0.7, FWIII 0.3–0.4, N = 5), with dorso-terminal groove and cover rounded distally; (5) fourth toe disc moderately wider than toe width (male TDIV 0.7–0.8, TWIV 0.3–0.5, N = 5), with dorso-terminal groove and cover notched distally; (6) presence of two palmar tubercles; (7) foot webbing moderately large, fourth toe webbing nearly extending up to the first subarticular tubercle on either side; (8) thigh nearly equal to shank (male TL/SHL ratio 98–100%, N = 5); and (9) shank nearly equal to foot length (male SHL/FOL ratio 98.1–102%, N = 5).

Morphological comparison. Nyctibatrachus athirappillyensis 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 relatively smaller snout-vent size, male SVL 20.9–22.8 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). Nyctibatrachus athirappillyensis differs from N. aliciae , N. deveni , N. pillaii , N. shiradi and N. vasanthi by its dorsal skin less prominently wrinkled and/or granular (vs. prominently wrinkled and/or granular in all five species), and third finger disc with dorso-terminal groove and cover rounded distally (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 ). Nyctibatrachus athirappillyensis differs from N. anamallaiensis, Garg et al. (2017) , PeerJ, DOI 10.7717/peerj.3007 10/50 N. beddomii , N. manalari sp. nov., N. minimus , N. pulivijayani sp. nov., N. robinmoorei sp. nov. and N. sabarimalai sp. nov. by its relatively larger male snout-vent size, male SVL 20.9–22.8 mm (vs. smaller, male SVL 10.0–18.0 mm) and presence of webbing between toes (vs. absent).

Because of the comparable snout-vent size, Nyctibatrachus athirappillyensis could be confused with the previously known species N. deccanensis , N. kempholeyensis and N. minor , and the new species N. webilla sp. nov. However, N. athirappillyensis differs from N. deccanensis by its relatively large snout-vent size, male SVL 20.9–22.8, N = 5 (vs. male SVL 16.1–20.8, N = 15), head width subequal or equal to head length, male HW/HL ratio 96.3–100%, N = 5 (vs. head wider than long, male HW/HL ratio 101.3–125.8%, N = 15), snout length relatively larger than head length, male SL/HL ratio of 41.8–48.1%, N = 5 (vs. male SL/HL ratio of 30.0–38.7%, N = 15), third finger disc with dorso-terminal groove and cover rounded distally (vs. without groove), fourth toe disc with dorso-terminal groove and cover notched distally (vs. with dorso-terminal groove and cover bifurcate distally), fourth toe webbing nearly extending up to the first subarticular tubercle on either side, I1–1 3/4II1–2+III1–2+IV2+–1V (vs. up to the second subarticular tubercle on either side), and flesh or off white ventral coloration in life (vs. red, reddish-orange or reddish-brown).

Nyctibatrachus athirappillyensis differs from N. kempholeyensis by its snout vertical in lateral view (vs. rounded), presence of two palmar tubercles (vs. single), and fourth toe webbing nearly extending up to the first subarticular tubercle on either side, I1–1 3/4II1– 2+III1–2+IV2+–1V (vs. below, I1–2−II1–2 1/4III1–2 1/2IV2 1/2–1V).

Nyctibatrachus athirappillyensis differs from N. minor by its relatively larger snout-vent size, male SVL 20.9–22.8 mm, N = 5 (vs. male SVL 15.4–17.9 mm, N = 6), third finger disc with dorso-terminal groove and cover rounded distally (vs. with dorso-terminal

groove and cover bifurcate distally), fourth toe disc with dorso-terminal groove and cover notched distally (vs. with dorso-terminal groove and cover bifurcate distally), relatively shorter forearm length than hand length, male FAL/HAL ratio 65.5–69.8%, N = 5 (vs. male FAL/HAL ratio 72.1–78.9%, N = 6), and foot webbing large (vs. absence of webbing).

Nyctibatrachus athirappillyensis differs from N. webilla by its relatively larger snout-vent size, male SVL 20.9–22.8, N = 5 (vs. male SVL 18.7–20.7, N = 4), head width subequal or equal to head length, male HW/HL ratio 96.3–100%, N = 5 (vs. head wider than long, male HW/HL ratio 110.8–117.4%, N = 4), third finger disc with dorso-terminal groove and cover rounded distally (vs. without groove), fourth toe disc with dorso-terminal groove and cover notched distally (vs. with dorso-terminal groove and cover bifurcate distally), thigh nearly equal to shank, male TL/SHL ratio 98–100%, N = 5 (vs. longer, male TL/SHL ratio 106.9–111.1%, N = 4), shank nearly equal to foot length, male SHL/FOL ratio 98.1–102%, N = 5 (vs. shorter, male SHL/FOL ratio 90.0–93.5%, N = 4), fourth toe webbing nearly extending up to the first subarticular tubercle on either side, I1–1 3/4II1–2+III1–2+IV2+–1V (vs. just above the third subarticular tubercle, I2−–2−II2−–3III3−–4−IV4−–3−V), and flesh or off white ventral coloration in life (vs. red, reddish-orange or reddish-brown).

Description of holotype (measurements in mm). Adult male (SVL 20.9); head width

subequal to its length (HW 7.6, HL 7.7); snout nearly rounded in dorsal view, vertical in lateral view, its length (SL 3.7) longer than horizontal diameter of the eye (EL 2.4); loreal region obtuse with indistinct canthus rostralis; interorbital space flat, wider (IUE 2.5) than the upper eyelid (UEW 1.2) and internarial distance (IN 1.9); nostril closer to eye (EN 1.4) than the tip of snout (NS 1.7); tympanum indistinct; vomerine ridge present, bearing small teeth, with an angle of 45° to body axis, closer to each other than choanae, longer than the distance between them; tongue moderately large, emarginated, bearing no median lingual process; supratympanic fold weakly developed. Forearm (FAL 3.6)

shorter than hand length (HAL 5.4), fingers with dermal fringes, finger length formula: I <II <IV <III, finger discs slightly wide compared to finger width (FDI 0.5, FWI 0.4; FDII 0.5, FWII 0.3; FDIII 0.5, FWIII 0.4; FDIV 0.5, FWIV 0.4), finger disc with dorso-terminal groove, cover rounded distally; subarticular tubercles prominent, oval, single, all present; prepollex distinct, oval; two palmar tubercles, distinct, oval; nuptial pads present. Thigh length (TL 10.0) subequal to shank (SHL 10.2), and equal to foot (FOL 10.0), relative toe lengths I <II <V <III <IV, toe discs moderately wide compared to toe width (TDI 0.7, TWI 0.4; TDII 0.8, TWII 0.4; TDIII 0.9, TWIII 0.5; TDIV 0.8, TWIV 0.5; TDV 0.6, TWV

0.5), toe disc with dorso-terminal groove, cover notched distally; foot webbing moderately large: I1–1 3/4II1–2+III1–2+IV2+–1V, fourth toe webbing nearly extending up to the first subarticular tubercle on either side ( Figs. 2 K and 2L); subarticular tubercles well developed, oval, single, all present; inner metatarsal tubercle present, oval; outer metatarsal tubercle absent; dermal fringe along toes I and V present, weakly developed.

Skin of snout shagreened to granular, upper eyelids tuberculate, sides of head, anterior and posterior parts of back and upper and lower parts of flank weakly wrinkled with spinular projections; subocular gland prominent, extending from the posterior ventral border of the orbit towards the posterior axis of the mandibles; dorsal surfaces of forelimb, thigh and shank with weakly developed folds or wrinkles and spinular projections; a well developed ridge extending from the lip over the tip of the snout to between the nostrils, at which point it bifurcates, producing an inverted ‘Y’; a well developed glandular fold between the eyes; ventral surface of throat with weakly developed longitudinal folds, chest shagreened, prominent glandular projections on the margin of lower jaw, belly and limbs shagreened; a pair of prominent femoral glands present on the ventral surface of thighs ( Figs. 2 F–2H).

Colour of holotype. In life. Dorsal and lateral side of head greyish-brown with scattered black spots, upper eyelids dark brown ( Figs. 2 A and 2C); a dark brown stripe between the eyes demarcating a triangular light orangish-brown patch on the snout, a pair of light orangish-brown longitudinal dorsal bands starting from behind the eyelids and extending up to the middle of dorsum ( Fig. 2 C); forelimbs (including fingers) and hind limbs (including toes) light orangish-brown with dark brown transverse bands; white glandular projections on the throat margins, lateral surfaces of the head and abdomen, margins of limbs, fingers and toes; webbing grey with dark grey spots; femoral glands orangish-brown with brown spots ( Fig. 2 F). In preservation. Dorsum grey with scattered dark grey spots, a pair of light greyish-brown longitudinal dorsal bands starting from behind the eyelids and extending up to the middle of dorsum; limbs, fingers and toes light grey with dark grey cross-bands; ventral surfaces greyish-white with scattered dark grey spots on the throat, forelimbs and hindlimbs, margins of limbs darker in colour.

Variations. Morphometric data from five adult males and an adult female, including the holotype, is given in Table S6. Overall, the colour and meristic characters of the paratypes are similar to the holotype. Colour in preservation. ZSI/WGRC/V/A/892: dorsum darker grey with more prominent dark grey spots; ZSI/WGRC/V/A/893–895: dorsum uniformly darker grey, ventral surfaces of throat, forelimbs and hindlimbs with more prominent dark grey spots.

Secondary sexual characters. Male, femoral glands present, nuptial pad on finger I present. Female (ZSI/WGRC/V/A/896), small pigmented eggs present (diameter 1.1 ± 0.4mm, N = 10).

Vocalization. Male (ZSI/WGRC/V/A/893) of Nyctibatrachus athirappillyensis produced a single type of call with two distinct parts, hereafter termed part 1 and part 2. Calls were not delivered in groups and the call parts had a fixed order, i.e., part 1 followed by part 2. The duration of the entire call was 755.7 ms and had a dominant frequency of 3.4 kHz. Part 1 had a single pulse (non-pulsatile) and was 93.5 ms in duration. Part 1 had a rise time of 43.6 ms and was without any significant fall time (7.3 ms). The overall dominant frequency of part 1 was 1.6 kHz with three distinct frequency peaks. On the other hand, part 2 had a pulsatile temporal structure and was much longer in duration (595.8 ms) compared to part 1, with 25 unevenly spaced pulses delivered at a rate of 42.2 pulses/s. The amplitude envelope of part 2 was characterized by a short rise time of 1.7 ms, fall time of 593.5 ms, and the overall dominant frequency of 3.4 kHz with two distinct frequency peaks (Table S8; Figs. 3 A–3E). Air temperature at the time of recording: dry bulb 25 °C, wet bulb 24 °C. Distribution and natural history. Nyctibatrachus athirappillyensis is currently known only from its type locality in the southern Western Ghats state of Kerala. All the specimens were collected from shallow streams or marshy areas covered with thick vegetation or leaf litter. Collection site was located inside a secondary forest. Calling males were found hiding under vegetation either inside the shallow stream or on the edges. Calls were heard and recorded during the late evening between 18:00–22:00 h.

Remark. Biju et al. (2011) erroneously interpreted the ‘‘fourth toe disc with dorso-terminal groove, cover rounded distally’’ in Nyctibatrachus kempholeyensis . In the present study we confirm that the fourth toe disc of N. kempholeyensis has a dorso-terminal groove with cover notched distally.

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 2 Holotype of Nyctibatrachus athirappillyensis sp. nov. (ZSI / WGRC / V / A / 891). (A) Dorsolateral view, in life. (B) Size (SVL 20.9 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) Closeup 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.

Figure 3 Male advertisement calls of Nyctibatrachus athirappillyensis sp. nov. and Nyctibatrachus manalari sp. nov. (A – E) Nyctibatrachus athirappillyensis sp. nov. (A) 10 s segment. (B) 1 s segment showing part 1 (non-pulsatile) and part 2 (pulsatile) of a single call. (C) 0.1 s segment showing the part 2 of a single call. (D) 0.1 s segment showing the part 1 of a single call. (E) Spectrogram of 1 s call segment. (F – I) Nyctibatrachus manalari sp. nov. (F) 10 s segment. (G) 1 s segment. (H) 0.1 s segment showing a single non-pulsatile call. (I) Spectrogram of 1 s call segment.