Beddomixalus, Abraham, Robin Kurian, Pyron, R. Alexander, Zachariah, Arun & Zachariah, Anil, 2013

Abraham, Robin Kurian, Pyron, R. Alexander, Zachariah, Arun & Zachariah, Anil, 2013, Two novel genera and one new species of treefrog (Anura: Rhacophoridae) highlight cryptic diversity in the Western Ghats of India, Zootaxa 3640 (2), pp. 177-189 : 180-181

Beddomixalus gen. nov.

( Fig. 2 C–D)

Type species: Polypedates bijui Zachariah et al., 2011

Etymology: The generic epithet is derived from a combination of the cognomen of Colonel Richard Henry Beddome, in honor of his pioneering and extensive fieldwork, which contributed to a fundamental understanding of amphibian diversity of the Western Ghats during the colonial period, and Ixalus ( Dumeril & Bibron, 1839) , often used as a suffix for names of rhacophorid genera. Gender is masculine.

Material examined: ZSI/ WGRC / V/A/842, 843, 844, adult males, Kadalar; ZSI/ WGRC / V/A/849, adult female, Kadalar; TNHM (H) 12.6.18 /54, adult male, Kadalar; TNHM (H) 12.6.18 /73, tadpole, Kadalar. Measurements of specimens provided in Table 1.

Diagnosis: Beddomixalus differs from all other rhacophorid genera by a combination of the following characters: a slender, elongated medium-sized frog (average male SVL 40.1, N=3; female SVL 60.8mm, N=1); dorsum yellowish-buff or reddish-brown in colour with two distinct yellowish-cream coloured parallel longitudinal stripes, extending from the supratympanic fold to the vent along the dorsolateral margin; vomerine teeth and lingual papilla absent; supratympanic fold and tympanum distinct; canthus rostralis rounded, loreal region obtusely concave (the canthus rostralis and the loreal region had been erroneously interpreted in the type description as being concave and angular, respectively); Wolffian duct simple, tubular ( Fig. 6 ). Additionally, early development of non-pigmented eggs occur exposed on moist swamp beds, without any form of protection, neither in the form of foam nests or parental care; has free-living aquatic tadpoles adapted to lentic conditions; inhabits mid- to highelevation forests. Beddomixalus currently contains one species and this diagnosis is valid for the genus and species.

Colour in life: Male: dorsum buff-brown with a dark stripe between the eyes in the inter-orbital region; a dark stripe extending medially from inter-orbital region to vent; two prominent light-coloured, yellowish-cream longitudinal stripes extending along the dorsolateral region, from the outer border of upper eyelid to the groin, on either side of the body, bordered on the lower side by a series of black dots, which appear as a line; a broad dark band extending from below the snout along the tympanum up to the middle of the flank, where it transforms into a pale patch covered in dark-brown to black vermiculations. Female: reddish- to orange-brown dorsum; similar dark and light bands and vermiculations as in the male; ventral surface white.

Geographic distribution: B. bijui is found in mid- to high-elevation (1100 – 1600m ASL) evergreen forests along the western slopes of the Eravikulam plateau ( Fig. 7 ). We recorded the species in the Mankulam forest division (10.1344N, 76.9947E; 1431m ASL) of Idukki district and the higher parts of the Malayattoor forest division (10.1869N, 76.9928E; 1584m ASL) of Ernakulam district in Kerala, and also on the Valparai plateau in the Anamalai Hills of Tamil Nadu (10.2756N, 77.0067E; 1246m ASL).

Breeding behaviour and reproductive mode: The species is primarily arboreal and inhabits trees in and around seasonal highland swamps or marshes ( Fig. 2 B). We carried out observations on breeding and development from April to July 2012. During the early part of the breeding season (late April to early June), hundreds of males aggregated around optimal breeding locations in moist swamp beds that were not yet filled with water. Males begin migrating towards breeding sites (swamp beds) ( Fig. 2 B) during the onset of pre-monsoon showers in late April from surrounding forest ( Fig. 2 A), where they congregate. These highland swamps are few in number and form part of the headwaters of regional streams and the substrate is mostly moist clay in April, when the pre-monsoon showers begin. Most males perch on shrubs and bushes (at up to 2m height) along the periphery of the dry swamp and in unison make a pulsating breeding chorus (audio file of call deposited in the Dryad Repository as Supplementary file 1; http://dx.doi.org/10.5061/dryad.pm166). But, individual males that occupy territories on shrubs within the swamp bed make a different call that could not be recorded ( Fig. 2 C), akin to that of some Polypedates spp. from Southern India. The air was dominated by a strong odour, which was reminiscent of the ‘burnt rubber’ smell characteristic of aggregating males of Hylarana malabarica ( Daniel, 1976) . Close examination of individual males suggested this odour to be produced by glands on their dorsolateral margin. Such an ambient odour and loud pulsating call could be reason for prompting males to form mass aggregations and attracting females, but further observations are needed to validate this. Males descend from their calling perches as the night progresses and occupy positions closer to grass patches in the muddy swamp bed.

In spite of several nights (n = 7) of observation, only two individual females could be located and followed to make observations of reproductive behaviour. Amplexus is pectoral ( Fig. 2 D) and an amplectant pair was observed moving within the swamp. The pair initiated oviposition on wet grass within the swamp basin. Non-pigmented, semiterrestrial eggs (terminology of Altig and McDiarmid 2007) (average diameter of an egg when freshly laid = 3.2mm) were scattered on moist soil or a grassy substrate, either as scattered loose arrays or in clumps (terminology of Altig and McDiarmid 2007; Fig. 2 E). Total clutch size was 175 eggs. Clutches of eggs deposited by other individuals were observed on wet clay. Eggs scattered on exposed rocks were seen to have desiccated the next day. Subsequent rains over the next few days raised the water level of the swamp, after which free-swimming tadpoles could be observed.

Tadpole morphology: Five tadpoles at various stages were collected within or close to grassy agglomerations in a swamp pool on 22nd June, 2012. Sample tissue from a tadpole was DNA sequenced and analyzed to determine its species status. Description is based on a single tadpole [TNHM (H) 12.6.22 /73] in Stage 38 ( Fig. 3 A-C). The small exotrophic, nektonic tadpole is oval and depressed ( Fig. 2 F) and is consistently dark pigmented from the snout to the tip of the tail, including fins. The ventral and ventrolateral body sides are pale pink and less pigmented. Eyes are reddish and of moderate size, positioned dorsolaterally and directed more laterally than anteriorly; not visible in ventral view. In lateral view, the body is slightly depressed, and snout slightly rounded. The musculus interhyoideus and intestine are visible through the ventral parts of the body. Naris equidistant from both snout and eye. Spiracle sinistral, ventrolaterally positioned at midbody. Myotomes of the tail musculature of moderate development. Tail fin moderate, rounded at the end. Upper fin smaller than lower fin. Oral disc anteroventrally positioned, of triangular shape in relaxed state, of oval shape in expanded state, and slightly emarginated laterally. Marginal papillae frame the oral disc ventrally and laterally, but absent on the upper labium. Small submarginal papillae cover the entire inner rim of oral disc. Upper jaw sheath narrow and stretched into a wide U-shaped arch. Lower jaw sheath V-shaped. Labial tooth row formula (LTRF) is 5(2-5)/3 (see Fig. 3 B).

Measurements (mm) of the representative tadpole were as follows: 29.1 total length from tip of snout to tip of tail, 9.9 body length as the distance from the tip of the snout to the junction of the body and tail, 20.3 tail length from the bodytail junction to the tip of the tail, 5.6 body width at the plane of the spiracle, 4.1 body height at the plane of the eyes, 2.7 tail muscle height at the base of the tail, 2.4 tail muscle width at the base of the tail, 1.2 maximum upper fin height, 1.3 maximum lower fin height, 4.9 maximum tail height including the fins, 1.1 eyenaris distance between the centres of the nares to the anterior edge of the eyes, 1.8 naris-snout distance between the centres of the narial apertures to tip of snout, 7.0 snout-spiracle distance from the tip of the snout and the terminal end of the spiracle, 1.7 internarial distance between the centres of the narial apertures, 1.5 interorbital distance between the medial borders of the eyes, and 1.5 eye diameter.

Larval metamorphosis: We observed tadpoles with completely developed hindlimbs at Stage 40 ( Fig. 3 D) in the first week of July. A pale dorsolateral band appears at Stage 42 ( Fig. 3 E). Eyes are bright red and overall body pigmentation changes to greenish-yellow by Stage 44 ( Fig. 3 F), when metamorphs begin emerging on land. At Stage 46, froglets can be found among vegetation surrounding the swamp ( Fig. 3 G).

Figures

FIGURE 2. Beddomixalus gen. nov. bijui A. general habitat comprising of tropical montane wet forests interspersed with tea plantations B. highland swamp, arrow = swamp pool after pre-monsoon showers; C. vocalizing male; D. pair in amplexus; E. eggs laid as clumps on grass in the swamp bed; F. free-swimming tadpoles in swamp pool.

FIGURE 3. Tadpole of Beddomixalus bijui; A. lateral view, B. details of oral apparatus (LTRF: 5 (2 - 5) / 3) and C. ventral view (Stage 38, 29.1 mm TL); metamorphic development of tadpole, D. Stage 40; E. Stage 42; F. Stage 44; G. Stage 46.

FIGURE 6. Diagram of a pair of simple tubular Wolffian Ducts and associated organs of a male Beddomixalus bijui. Notations: A = Kidneys, B = Testes, C = Fat Bodies, WD = Wolffian Duct.

FIGURE 7. Map showing distribution of Mercurana myristicapalustris gen. et sp. nov. and Beddomixalus gen. nov. bijui in the southern Western Ghats, India; coloured markers indicate type localities.