Leptobrachium rakhinensis Wogan

Wogan, Guinevere O. U., 2012, A new species of Leptobrachium from Myanmar (Anura: Megophryidae), Zootaxa 3415, pp. 23-36 : 27-32

Leptobrachium rakhinensis Wogan sp. nov.

Figures 3, 4, 5

Synonymies: Leptobrachium hasseltii Frost, Grant, Faivovich, Bain, Haas, Haddad, De Sa, Channing, Wilkinson, Donnellan, Raxworthy, Campbell, Blotto, Moier, Drewes, Nussbaum, Lynch, Green, Wheeler. 2006 : Bulletin of the American Museum of Natural Hististory. 297: 50 Leptobrachium sp. 3 Matsui, Hamidy, Murphy, Khonsue, Yambum, Shimada, Ahmad, Belabut, Jiang. 2010. Molecular Phylogenetics and Evolution. 56: 262, 263, 265, 267, 270.

Holotype: CAS 222296, adult male collected in Myanmar, Rakhine State, Gwa Township, Rakhine Yoma Elephant Sanctuary [N 17° 42´14.0´´ E 94° 38´54.3´´], on April 27, 2001, by J. B. Slowinski, G. O. U. Wogan, Htun Win, Thin Thin, Kyi Soe Lwin, Awan Khwi Shein, and Hla Tun.

Paratypes: CAS 239633, adult female collected in Myanmar, Bago Division, Pyi District, Padaung Township, Nyaung Gwo village [N 18° 39´36.8´´ E 94° 50´09.0´´], September 28, 2007 by San Lwin Oo, Awan Khwi Shein, Mau Win, Kyi Soe Lwin and Ye Myo Win at 2923 ft elevation; CAS 239593, adult male collected in Myanmar, Bago Division, Pyi District, Padaung Township, Nyaung Gyo village [N 18° 39´24.0´´ E 94° 50´38.5´´], September 27, 2007 by San Lwin Oo, Awan Khwi Shein, Mau Win, Kyi Soe Lwin and Ye Myo Win at 2669 ft. elevation. CAS 239584, adult male collected in Myanmar, Bago Division, Pyi District, Nyaung Gyo village [N 18° 39´24.0´´ E 94° 50´38.5´´], September 27, 2007 by San Lwin Oo, Awan Khwi Shein, Mau Win, Kyi Soe Lwin and Ye Myo Win at 2669 ft. elevation. CAS 239678, adult female collected in Myanmar, Bago Division, Pyi District, Nyaung Gyo village [N 18° 39´36.8´´ E 94 49´46.5´´], October 1, 2007 by Awan Khwi Shein, San Lwin Oo, and T.H. Win at 3091 feet elevation. CAS 239654, adult female collected in Myanmar, Bago Division, Pyi District, Nyaung Gyo village [N 18° 39´24.0´´ E 94° 50´38.5´´], September 29, 2007 at 2674 feet elevation. USNM (JBS20758), adult female collected in Myanmar, Bago Division, Pyi District, Nyaung Gyo village [N 18° 39´36.8´´ E 94° 49´46.5´´].

FIGURE 3. The holotype of Leptobrachium rakhinensis ( CAS 222296) in life. Photo by Hla Tun. Copyright 2001 California Academy of Sciences.

Diagnosis. Referable to the genus Leptobrachium based on molecular phylogenetic evidence and the possession of a suite of morphological features characterstic of the genus, such as large axillary glands, the shank length shorter than head width, and a bi-colored iris ( Dubois and Ohler 1998). It is a medium sized frog with male SVL ranging from 48–57 mm, and female SVL ranging from 57–66 mm. Head width and length sub-equal, generally slightly longer than wide, an indistinct tympanum, supratympanic fold distinct extending from behind eye to arm insertion, skin smooth except for some faint tubercles ventral to the tympanum, and femoral and axillary glands. Head with distinctive inverted Y shaped mark extending from between the eyes to the snout, two strings of dark blotches stretch dorsolaterally and laterally sometimes forming dark irregular lines, iris is bicolored red and black with the upper half red, and a light blue scleral arc under the eyelid, males with a single vocal sac, mature males lack lip spinules.

FIGURE 4. The holotype of Leptobrachium rakhinensis (CAS 222296) dorsal and ventral views.

FIGURE 5. Hand and foot morphology of the Leptobrachium rakhinensis holotype (CAS 222296).

Description of Holotype. A robust individual of medium size, head longer than wide, snout rounded not projecting beyond lower jaw, pineal ocellus absent, tympanum hidden and not depressed relative to surrounding area, supratympanic ridge distinct extending from behind eye to should insertion. Canthus rostralis weak, ridge from anterior of eye to nostril present. Nostrils round with a dorsolateral orientation, located closer to tip of snout than to eye. Tongue entire, broad, and unnotched. Iris bicolored red and black, sclera light blue (in life). Forelimbs slender, tips of fingers not expanded and round; relative length of fingers II<IV<I<III; fingers with weak dermal fringes, tubercles on fingers form elongate callous ridges, two strong palmer tubercles present, both semi-circular. Tips of toes not expanded; relative lengths of toes I<II<V<III<IV. Toes with thick webbing I1.5- 3 II1- 3 III2-3.5IV4- 3V (following Myers and Duellman 1982), and extensive dermal fringing reaching to the toe tips. Tarsal fold absent. Inner metatarsal tubercle large, flat and distinct, outer metatarsal tubercle absent. Skin smooth with a few white granules located ventral to the tympanum. A weak supratympanic ridge from eye to shoulder insertion. A round white axillary gland is located close to the arm insertion. A small white very indistinct oblong femoral gland present on the posterior of each thigh closer to knee than to vent.

Color in alcohol. Dorsum brown grey with discrete dark markings. The marking between the eyes is conserved among the specimens and consists of a thin elongate spot that stretches from between the eyes onto the snout, between the eyes the spot broadens into two triangle shapes which stretch on to the eyes. The entire spot is lightly outlined with white. A second mid dorsal “ Y ” shaped spot begins just posterior to the eyes and broadens between the shoulders, also faintly outlined in white. On either side of this spot an irregular elongate spot stretches back followed by a series of smaller spots to the sacral area all are also outlined in white. The rest of the dorsum has irregular dark spots. A broad dark irregular canthal streak is edged in white. A dark bar reaches from below the eye the mouth. A dark line follows the tympanic line from behind the eye to the shoulder. The tympanum is encased in black and can be distinguished by its brown coloration. Behind the tympanum a second series of spots reaches back halfway to the sacral region. Below this are small white speckles. The ventrum is light colored with small white speckles. The throat is dark brown with small white spots. The forelimbs are barred with a few thin dark lines. The hind limbs are barred with thin dark lines. The back of the thighs have white spots and white femoral glands.

Color in life. As in preservative with a light gray background and dark gray spots. The iris was bicolored red and black and a light blue sclera was apparent (Figure 3).

Variation within the paratype series. The paratypes are in general agreement with the holotype description with the following variations: in all of the paratypes, the digit tips are more ball-like than in the holotype specimen.

Natural history and reproductive behavior. This species inhabits low elevation monsoonal rainforest, and has been found in the Myanmar Coastal Rainforest and Mizarom-Manipur Kachin Rainforest ecoregions ( Olson et al., 2001). The holotype was found moving in thick leaf litter or among rocks in small waterfalls in streams. The paratypes were found in primary evergreen rain forest. Two individuals (not collected) were observed being preyed upon by a large centipede (Scolopendromorpha; Scolopendra). In both instances the centipede had eaten the legs off of the frog.

Not much is known about the reproductive behavior of this species. Males were observed calling from the ground in leaf litter in September (end of monsoon season). Females collected in September were gravid; the eggs of the species are cream colored, not bicolored.

Range. In Myanmar this species has been found in the Rakhine Hills (in Rakhine and Bago States) (Figure 6). Outside of Myanmar it may also occur in N.E. India and Bangladesh (see discussion).

Comparisons. In life, Leptobrachium rakhinensis differs from L. hainanense , L. chapaense , L. xanthospilum , L. banae , L. bompu , L. gunungense , L. nigrops , L. kanowitense , L. ingeri , L. buchardi . L. montanum , L. leucops , L. xanthops and L. abbotti in possessing a bicolor red and black iris. L. rakhinensis differs from the following congeneric historically red and black bicolored iris taxa by the following suites of characters (refer Table 3): L. hasseltii possesses a black eye with a blue sclera, it also has distinct tuberculate ridges on the forelimbs and has a white ventrum with small dark spots ( Ohler et al., 2004). L. rakhinensis (males 48 to 57, females 57 to 66) is larger than L. hasseltii (males 37 to 48, females 53 to 63 ( Brown et al., 2009)), and is less size dimorphic than L. hasseltii . L. hasseltii either lacks or has a very narrow canthal stripe, while in L. rakhinensis it is broad. L. hasseltii is found on Islands in Indonesia and is more closely related to Sundaland species such as L. hendricksoni and L. nigrops than to L. rakhinensis . L. pullum has a black eye with a red sclera, it lacks dark ventral markings, has white lateral spots, and light tibial barsIt possesses a very large inner metatarsal tubercle and forelimbs with light bars. The shape of the snout of L. pullum projects beyond the nares (refer Figure 2 in Matsui et al 1999 of the paralectotype BM 1921.5.5.31. L. rakhinensis lacks the orange wash observed in L. pullum ( Stuart et al., 2011) . L. pullum does not have head markings, nor does it have a canthal stripe, both are pronounced in L. rakhinensis . L. pullum is more closely related to east Asian species than to L. rakhinensis . L. rakhinensis can be differentiated from other redblack bicolored iris taxa as follows: L. hendricksoni lacks dark markings on the dorsum and the marking on the head may or may not be distinct ( Taylor 1962). It also lacks bars on the limbs ( Lathrop 1998). Furthermore, L. hendricksoni is phylogenetically more closely related to Sundaland species such as L. hasseltii and L. nigrops than to L. rakhinensis . L. rakhinensis is most similar to L. smithi , however the two species are distinguishable by the following suite of morphological characters; L. rakhinensis has a lateral series of dark spots and small white speckles while L. smithi lacks the white speckles. The ventral patterns differ, with L. smithi possessing a white ventrum with dark splotches, and L. rakhinensis possessing a light (not white) colored ventrum without splotches. The holotype possesses some faint netlike reticulations while the other individuals all have immaculate ventra. L. smithi possesses mottling on the ventral side of the hindlimbs (absent in L. rakhinenesis ), very distinctive fore and hind leg stripes, and the posterior of the thighs is black, While in L. rakhinens is the leg bars are not as distinctive and the posterior of the thighs is white spotted. The eggs of L. rakhinensis are cream colored, not bicolored as in L. smithi . L. rakhinensis is less size dimorphic than L. smithi , and finally, the two species are genetically diverged.

Etymology. The specific epithet is derived from the name of the mountain range (The Rakhine Yoma) and political province (Rakhine State) where this species was first encountered.

FIGURE 6. Distribution map of Leptobrachium rakhinensis in Myanmar. The type locality is designated with a star.