Micryletta subaraji, Sankar & Law & Law & Shivaram & Abraham & Chan, 2022

Sankar, Ananthanarayanan, Law, Ingg Thong, Law, Ing Sind, Shivaram, Rasu, Abraham, Robin K. & Chan, Kin Onn, 2022, Morphology, phylogeny, and species delimitation of Micryletta (Anura: Microhylidae) reveals a new species from Singapore, Vertebrate Zoology 72, pp. 457-467 : 457

Micryletta subaraji sp. nov.

Figs 1B , 6 , 7

Micryletta inornata Law, Thomas, and Law, 2019: 5

Suggested Common Name.

Subaraj’s Paddy Frog.

Holotype.

ZRC1.13370 (Fig. 6 ), adult male, collected 8th January 2021, 2130H from Kranji Marshes, Singapore (1°25.1150'N, 103°43.2641'E, 8 m a.s.l) by Law Ing Sind and Law Ingg Thong.

Paratypes (n=8).

ZRC 1.13369, adult male; ZRC 1.13389, adult male; ZRC 1.13469, adult male; ZRC 1.13470, adult male; ZRC 1.13323, adult female; ZRC 1.13466, adult female; ZRC 1.13467, adult female; ZRC 1.13468, adult female; all collected from the same location as the holotype between January and October 2021 by Law Ing Sind, Law Ingg Thong, and Sankar Ananthanarayanan (Fig. 7 ).

Diagnosis.

Micryletta subaraji sp. nov. is a member of Micryletta based on its sister relationship to Micryletta inornata s.s. (Fig. 3 ). It can be distinguished from other members of the genus by a combination of the following characters: small body size (SVL 18.90 mm in males, 23.04 mm in females), an abruptly rounded snout, lack of webbing between fingers and toes, lack of distinct supratympanic fold, tympanum hidden, the presence of a circular inner metatarsal tubercle, and the absence of an outer metatarsal tubercle. Males of Micryletta subaraji sp. nov. can be distinguished from males of its sister species M. inornata s.s. from their significantly larger head proportions (head width, head length, snout length, nostril-eye length, snout-nostril length, upper eye-lid diameter) and shorter tibiofibula length.

Description of holotype.

Adult male, SVL 18.9 mm; habitus slender; head slightly wider than long (HW/HL 1.05), acuminate in dorsal profile with abruptly rounded snout; snout length (SL 2.41 mm) roughly equal to eye diameter (EL 2.39 mm), and slightly longer than interorbital distance (IOD 2.26 mm); nostrils closer to tip of snout (S-NL 1.15 mm) than to anterior tip of eye (N-EL 1.26 mm); interorbital distance larger than internarial distance (IND 1.76 mm); eyes large, 38% of head length; pupil round and moderately dilated; tympanum not visible, and supratympanic fold not present. Skin on dorsal and ventral surfaces smooth; forelimbs and hindlimbs slender; F3>F4>F2>F1, T4>T3>T5>T2>T1; fingertips and toetips lacking in discs; no webbing between fingers and toes; circular basal subarticular tubercles on all fingers and toes; circular supernumerary metacarpal tubercles present at the base of F2, F3, and F4, palmar tubercle well-developed and circular, thenar tubercle and outer metacarpal tubercle circular; inner metatarsal tubercle circular, outer metatarsal tubercle absent (Fig. 6 ).

Dorsum greyish brown; forelimbs and hindlimbs light brown with dark brown mottling; one dark brown broken vertebral stripe, with broken paravertebral stripes on each side; strong dark brown cephalic mottling in between eyelids A solid black lateral stripe from the tip of snout, past eye, remains unbroken until forearm, becomes a dark mottling between forelimb and hindlimb, where it terminates; a thin cream stripe runs parallel below the eyestripe, starts at nostril, terminates at forelimb. Venter cream with dark brown to grey mottling under sides of belly; inner legs are immaculate and uniformly light cream, tibiofibula is moderately mottled, bottom of tarsus is light brown. Stippling is more apparent under a microscope. Black gular sac (Fig. 6 ).

Variation.

Raw mensural data are presented in Table 1 . Males generally have smaller body sizes than females, although there is overlap in the ranges of values (male SVL 17.45-18.90 mm, female SVL 16.94-23.04 mm). Female ZRC1.13323, which is visibly gravid, is the largest specimen in the series. The holotype is largely representative of the type series, and minimal variation is observed in colouration (Fig. 3A, B ). Males all possess a black gular sac. Most specimens have visible dark brown mottling on cream venters. However, this mottling is absent or indistinct in juvenile ZRC 1.13390, juvenile ZRC 1.13465, male ZRC 1.13389, and female ZRC 1.13467 (Fig. 7 ).

Distribution.

Micryletta subaraji sp. nov. is so far only known from Singapore where it occurs in Kranji Marshes and putatively in the Central Catchment Nature Reserve. It may also occur in other parts of the island where suitable habitat is present.

Etymology.

The specific epithet honours the late Mr. Subaraj Rajathurai, who is a pioneer of conservation in Singapore.

Natural History.

In addition to the collected specimens, male advertisement calls were heard at an ephemeral pool in a depression created by an uprooted tree. The calling individuals were perched amidst dense undergrowth surrounding this puddle. These ephemeral depressions may be used by male frogs as a means to amplify their advertisement calls. Several other Microhylids (both native and introduced) were recorded in sympatry at the type locality including Microhyla heymonsi , Microhyla butleri , Microhyla cf. mukhlesuri , and Kaloula pulchra .

Figures

Figure 1. A Distribution of confirmed localities of Micryletta inornata s. s. from Sumatra and Myanmar (blue diamonds) and M. cf. inornata from Kranji Marshes (green circle), and Central Catchment Nature Reserve (white circle) in Singapore. B Photo showing M. cf. inornata in life. C Degraded habitat at Kranji Marshes that M. cf. inornata specimens were detected in. Photos by Law Ingg Thong.

Figure 3. Maximum likelihood phylogeny based on 1,097 bps of the 16 S rRNA mitochondrial gene. Nominal species and their regional distribution ranges are labeled to the right of the phylogeny. The clade containing M. cf. inornata from Singapore is highlighted in green. BS = ultrafast bootstrap support values.

Figure 6. Holotype of Micryletta subaraji sp. nov. (ZRC 1.13370, Male) from Kranji Marshes. A Dorsal view. B Ventral view. C Right lateral view of head. D Ventral view of left hand. E Ventral view of left foot. Photos by Shivaram Rasu

Figure 7. Type series of Micryletta subaraji sp. nov. from Kranji Marshes in (A) dorsal views and (B) ventral views. The holotype specimen (ZRC 1.13370) is on the extreme left side of both panels.