Microhyla mihintalei, Wijayathilaka, Nayana, Garg, Sonali, Senevirathne, Gayani, Karunarathna, Nuwan, Biju, S. D. & Meegaskumbura, Madhava, 2016

Wijayathilaka, Nayana, Garg, Sonali, Senevirathne, Gayani, Karunarathna, Nuwan, Biju, S. D. & Meegaskumbura, Madhava, 2016, A new species of Microhyla (Anura: Microhylidae) from Sri Lanka: an integrative taxonomic approach, Zootaxa 4066 (3), pp. 331-342 : 334-338

Microhyla mihintalei sp. nov.

( Figures 1–4 ; Table 1)

Suggested common name. Mihintale Red Narrow-mouthed Frog.

Etymology. The species is named after Mihintale, the point of unison for two ancient cultures when Mahinda Thero (Son of Indian Emperor, Asoka) met Dewanampiya Tissa (the king of Anuradhapura, Sri Lanka) in 246 BC. Mihintale is also considered to be one of the world’s earliest sanctuaries. The species epithet mihintalei is a noun in apposition to the generic name.

Holotype. Adult male (DZ 1553), Anuradhapura (8.3541°N, 80.3967°E, 90 m a.s.l) Anuradhapura Sri Lanka, collected by NW and team, 22 December 2014.

Paratypes. Four adult males (DZ 1554–1557), collected along with the holotype; three adult males (DZ 1467, DZ 1468, DZ 1473) collected from the same locality, collected by NW and team, 12 October 2012; one adult male (DZ 1410) and one female (DZ 1418), from Maakandura (7.3245°N, 79.9887°E, 30 m a.s.l.), Kurunegala district, Sri Lanka, collected by MM and team, 28 August 2014; one adult male (DZ 1457), from Ampara (7.2932°N, 81.6704°E, 30 m a.s.l.), Ampara district, Sri Lanka, collected by NW and team, 10 October 2014; two adult males (DZ 1445–1446), from Mihintale (8.3548°N, 80.5054°E, 120 m a.s.l.), Anuradhapura district, Sri Lanka, collected by MM and team, 2 October 2014; one adult male (DZ 1127), from Dambulla (7.8584°N, 80.6773°E, 190 m a.s.l.), Matale district, Sri Lanka, collected by MM and team, 4 January 2013.

Diagnosis. We allocate these specimens to Microhyla since they show the following diagnostic characters for this genus ( Parker 1934): narrow head; eyes reduced; maxillary and vomerine teeth absent; fingers without webbing; toes with basal webbing; prominent inner metatarsal tubercle on foot ( Fig. 1 ). Microhyla mihintalei sp. nov. is diagnosable from its congeners by the combination of following characters: small-sized, slender body, adult male SVL 21.7–27.3 mm (N = 13), adult female SVL 24.4 mm (N = 1); tympanum indistinct or obscured by a layer of skin without clearly defined borders; vomerine ridge absent; tongue elliptical; finger and toe tips rounded without marginal grooves; webbing between toes rudimentary; inner and outer metatarsal tubercles present.

Morphological comparisons. Microhyla mihintalei sp. nov. is closely related to Microhyla rubra based on molecular evidence and overall external morphology, however differs from the latter by its relatively smaller adult male size, SVL 21.7–27.3 mm, N = 13 (vs. larger SVL 25.8–29.6 mm, N = 8); dorsal skin shagreened to sparsely granular (vs. granular); thigh equal to shank and foot length, male, TL 11.6 ± 0.6 mm, SHL 11.7 ± 0.6 mm, FOL 11.6 ± 0.6 mm, N = 14 (vs. longer, male, TL 13.8 ± 0.5 mm, SHL 11.9 ± 0.2 mm, FOL 12.4 ± 0.4 mm, N = 8). Mann-Whitney U test results suggest that the two congeners are significantly different in SVL, HW, HL, SL, UEW, TL, FAL, HAL and FOL (Appendix 1). The new species is not conspecific with any of the other known species from the Western Ghats of India and Sri Lanka. However, for the purpose of more clarity and to avoid possible confusions, a comparison with the other four valid species known from this region is being provided. Microhyla mihintalei sp. nov. differs from M. karunaratnei and M. zeylanica from Sri Lanka, and M. ornata and M. sholigari Dutta and Ray, 2000 from the Western Ghats, by its relatively large snout-vent size of the adult male, SVL 21.7– 27.3 mm, N = 13 (vs. SVL 15.8–19.1 mm, N = 11; SVL 11.8–20.0 mm, N = 5; SVL 14.5 – 20.3 mm, N = 5; SVL 17.5 – 24.8 mm, N = 7, respectively). Specifically, the new species differs from M. karunaratnei and M. sholigari by its non-dilated finger and toe tips without circum-marginal grooves (vs. dilated with circum-marginal grooves), differs from M. karunaratnei by its finger and toe disc rounded without dorso-terminal groove (vs. dilated with dorso-terminal groove), differs from M. ornata by its shovel-shaped metatarsal tubercle (vs. rounded nonshovelshaped).

Genetic comparison. Comparison of the uncorrected pairwise divergences of generated sequences representing four Sri Lankan populations, Dambulla (DZ 1127), Maakandura (DZ 1410, DZ 1418), Mihintale (DZ 1445, DZ 1446) and Anuradhapura (DZ 1468) of Microhyla mihintalei sp. nov., and one population of Microhyla rubra from Karnataka (SDBDU 2558), along with one available GenBank sequence ( AB 201192 ) show that the genetic divergences range between 2.7−3.2% for the two species (Appendix 2).

Acoustic comparison. PCA with unrotated axes on the correlation matrix of the call characters (involving eight variables: Call Duration, Number of Pulses, Pulse Rate, Dominant Frequency, Call Rise Time, Call Fall time, 50% Call Rise Time, 50% Call Fall Time) for the two species shows that Microhyla rubra from India separates out well from M. mihintalei in the PC space ( Fig. 2 ). The separation however is only attributable to the factors that contribute to the PC1 axis, which is explained mostly by Call Duration, Dominant Frequency, Call Rise Time and Pulse Rate (Pulse Rate loads negatively while the other three load positively). The two species overlap completely on PC2 axis ( Fig. 2 ), which is explained mostly by Call Fall time, Number of Pulses and Call Rise Time (Call Rise Time loads negatively and the other two load positively).

Holotype description (measurements in mm). Small-sized, adult male ( SVL 24.8). Head small ( HW 7.4, HL 6.2), shorter than wide, snout sub-ovoid in dorsal and ventral view, rounded in lateral view, its length ( SL 2.7) longer than horizontal diameter of eye (EL 2.3); loreal region rounded with vertical canthus rostralis; interorbital space wider (IUE 2.6) than upper eyelid ( UEW 1.5) and internarial distance (IN 1.8); nostril closer to tip of snout (NS 1.0) than eye (EN 1.4); tympanum indistinct or obscured by a layer of skin without clearly defined borders, supratympanic fold distinct, extending from posterior corner of upper eyelid to near the insertion of forelimb at axilla; eye diameter (EL 2.3); vomerine ridge absent; tongue elliptical. Forelimbs moderately short and thin; forelimb ( FAL 5.1) shorter than hand length ( HAL 6.0); fingers short, finger length formula I<IV<II<III; tips of all fingers without discs, rounded; subarticular tubercles prominent, rounded, all present ( Fig. 1 ); palmar tubercles three, well developed, oval. Hindlimbs relatively long and thin, thigh length ( TL 11.3) subequal to shank (SHL 11.5), and foot (FOL 11.6); relative digit lengths I<II<V<III<IV; tips of all toes without discs, rounded; webbing present: basal; weakly developed dermal ridge on all toes present; subarticular tubercles prominent, oval; two metatarsal tubercles, oval, shovel-shaped, outer one slightly larger than inner.

Skin of dorsum, snout, between eyes, sides of head, posterior part of back, upper and lower part of flanks and ventral surface smooth, dorsal parts of forelimb, thigh, tibia and tarsus smooth to shagreened.

Colour in preservation. Dorsum light brownish-grey with a broad light grey band extending from behind the eye to the groin; dorsal surface of forelimbs lighter in colour compared to the dorsum and with incomplete black cross-bands; lateral side of head and tympanic area dark grey; groin light grey with black patches; two distinct and narrow black streaks extending from the snout along the side of head to near the groin; posterior parts of thigh and tibia with irregular black markings; a narrow black patch extends from anal opening to near the knee; ventral surface creamy-white, throat with dark blackish-brown calling patch.

Colour in life ( Fig. 3 ). Dorsum light reddish-brown with a faint light grey band extending from behind the eye to the groin ( Fig. 3D ); lateral side of head and tympanic area dark grey; groin light grey with black patches; two distinct and narrow black streaks extending from the snout along the side of head to near the groin; posterior parts of thigh and tibia light brown with irregular black markings; a narrow black patch extends from anal opening to near the knee; ventral surface grey, throat with dark blackish-brown calling patch ( Fig. 3 ).

Variation. See Table 1 for morphometric data from 13 adult males and one female. DZ 1127 (in life): dorsum reddish-brown with brown band extending from behind the eye up to the groin, faint cross-bands on both limbs, lateral side of head and tympanic area light grey ( Fig. 3F ); DZ 1457 (in life: dorsum dark reddish-brown, lateral side of head and tympanic area dark grey; ventral surface light grey with dark grey reticulations especially on the throat; in preservation, light grey dorsum ( Fig. 3G ); DZ 1467 (in life): dark greyish-brown with dark brown dorsal band.

Secondary sexual characters. Males: Single vocal sac externally visible on lower jaw. Female (DZ 1418): ova, pigmented on poles (diameter 0.7–1.1 mm, N =15).

Distribution and Natural History. Microhyla mihintalei sp. nov. is found in the lowland dry zone ( Fig. 4 ), mostly in shaded areas, often close to stream and river banks or regions that become fairly stable ephemeral pools during the rainy season. They were observed emerging from borrows in ground to call by around 7.30 PM, slightly after the initiation of calling of M. ornata , a smaller sympatric species. Compared to M. ornata , the abundance of M. mihintalei sp. nov. is much lower, and so are the corresponding numbers of tadpoles in pools. In captivity, M. mihintalei was observed digging rapidly into soil using their hind feet. This indicates that they are active borrowers, and not only ground-burrow utilizers. They lay eggs as loosely arranged sheets on the water surface, mainly in ephemeral pools and their tadpoles also form loose shoals. The tadpole of M. mihintalei was described by Bowatte and Meegaskumbura (2011), however, as M. rubra from Sri Lanka.

Figures

FIGURE 1. Holotype of Microhyla mihintalei sp. nov. (DZ 1553, an adult male, SVL 24.8 mm). A. Dorsal view; B. ventral view; C. lateral view of head; D. ventral view of foot; E. ventral view of hand.

FIGURE 2. A – D. Oscillogram of advertisement calls (four consecutive calls and a single call) of males of Microhyla mihintalei sp. nov. and Microhyla rubra. A. four consecutive calls (time shown: 3 seconds); B. a single call (time shown: 0.3 seconds) of M. mihintalei sp. nov.; C. four consecutive calls (time shown: 3 seconds); D. a single call (time shown: 0.3 seconds) of M. rubra; E. PC 1 vs. PC 2 factor scores of the Principal Components Analysis of call characters for the two species.

FIGURE 3. A – G. Microhyla mihintalei sp. nov. in life. A – E. Holotype (DZ 1553, an adult male). A. dorsolateral view with a light-grey band extending from behind the eye to the groin; B. dorsal view showing the light reddish-brown dorsum; C. ventral view highlighting the dark blackish-brown calling patch; D. lateral view of thigh and groin; E. posterior view of thighs with irregular black markings; F. Paratype (DZ 1127, an adult male) in dorsal view; G. Paratype (DZ 1457, an adult male); H. Microhyla rubra in life (SDBDU 2559, an adult male), from Shivanahalli, Karnataka.

FIGURE 4. Distribution of Microhyla mihintalei sp. nov. in Sri Lanka indicating its wide distribution, right from sea-level up to 500 m a. s. l. Populations for which genetic data (16 S rRNA) were generated are denoted in red circles. Arrow indicates the call-recorded population from Mihintale.