Polypedates cf. megacephalus ( Hallowell, 1861 )

Raj, Prudhvi, Vasudevan, Karthikeyan, Dutta, Sushil Kumar, Sahoo, Gunanidhi, Mahapatra, Susmita & Sharma, Richa, 2023, Larval morphology of selected anuran species from India, Alytes 39 - 40, pp. 1-140 : 113-116

S27. Polypedates cf. megacephalus ( Hallowell, 1861) ( fig. 55‒56 )

Larval series examined. WT 131.5611( Mawblang , Cheerapunji, Meghalaya, India; 25.35453 N, 91.74230 E). Tadpoles were collected in a pool of one foot deep. The location of the pool was on a hill plateau. Substratum in the pool was both rocky and sandy with emergent vegetation and algal growth .

Notes. Sequence of 16S rRNA (OQ079501) generated from the tadpole voucher (WT 131) showed 1 % sequence divergence when compared to published Genbank sequence ( EU 215553 ) from a taxonomically identified specimen of Polypedates megacephalus . P. megacephalus has a wide distribution, and further taxonomic studies are required to ascertain the taxonomic status of the species from Northeast India.

External morphology. Description of a tadpole at Gosner stage 36. Body elliptical and triangular in dorsal and lateral perspectives ( fig. 55a‒b ). Body length 41.2 % of total length; maximum body diameter at the centre of abdomen. Snout rounded and acutely curved in dorsal and lateral perspectives. Eyes large, located and oriented laterally; distance between eye and nostril 59.3 % of distance between eye and snout. Nostril opening oval with protuberance on dorsal tip of opening; placed parallel to eye in dorsal view; closer to snout than to eye; inter-narial distance 55 % of inter-orbital distance. Spiracle sinistral; tube orientation posterolateral, its opening located below the medial and above the lateral side of venter; inner wall of tube not completely formed and attached to body wall. Distance between spiracle and snout 56 % of body length. Opening of vent tube dextral. Tail tip acutely pointed; musculature broad at body tail junction tapering beyond. Dorsal fin originating anterior to body tail junction, ventral fin originating at ventral terminus; dorsal and ventral fins of equal height; maximum height of caudal fin at mid-length. Height of tail muscle 1.28 times width of tail muscle at tail-body junction. Tail (caudal) musculature accounting for 40 % of height of tail. Lateral line conspicuous. Glands absent on outer integument.

Oral disc located anteroventrally, not visible dorsally ( fig. 55c ). Rostral width of oral disc 37.7 % of maximum body width, emarginated; single row of marginal papillae at lateral commissures and double row on lower labium; marginal papillae broadly interrupted on upper labium and narrowly interrupted on lower labium; four to five large submarginal papillae at lateral commissures; both labia of equal size. Labial tooth row formula A5(2‒5)/P3(1). Order of lengths of labial tooth rows A1> P1> A2> P2> P3> A3> A4> A5. Both jaw sheaths keratinized moderately. Jaw sheath margins uniformly serrated with small fine serrations; supra-rostrodont longer than wide and convex; infra-rostrodont U-shaped, convex laterally and concave medially.

Measurements of 30 tadpoles at various Gosner stages (25‒27, 29, 32‒36) are given in tab. 26 .

Coloration. In life, dorsal body and flanks brownish-black with numerous tiny melanophores. Ventrally, background opaque and dirty white with many tiny melanophores speckled across. Dorsal and ventral fins transparent and brownish; fins spotted with several tiny melanophores; anterior region of fins and tail musculature heavily speckled by melanophores. Spiracle, oral disc and vent tube translucent and dotted with many tiny melanophores.

Buccopharyngeal morphology. Buccal roof ( fig. 56a‒b ). Prenarial arena of roof with pustules arranged in an arch shape; four medially large pustules followed by three smaller pustules on either side. Internal nares transverse, oriented posteromedially; gap between nares moderate, about the length of each nare; anterior narial wall pustulose with few pustules and a tall conical papilla originating at lateral corner of wall; posterior wall tall, smooth and valvular with section near to medial raised as a flap. Postnarial arena with four conical papillae, two papillae located behind each narial wall arranged linearly and oriented medially; papillae near to mesad of roof larger, having a rugose surface on anterior margin. Median ridge papilla triangular with pustulated margin and pustulated tip. A long and broad lateral ridge papilla, perpendicular to median ridge; rugose on both margins. BRA demarcated with four pairs of long conical papillae on lateral border of roof; second pair papillae branched; about 40 tiny pustules spread across BRA. Glandular zone thick and broad; secretory pits present. Dorsal velum raised and discontinuous with tiny projections.

Buccal floor ( fig. 56c‒d ). Prelingual arena composed of two pustules at anterolateral corner and three palps at posterolateral corner on each side of jaw sheath; size of palps at posterolateral corner following ascending order with posterior palp largest and dilated among three palps at posterolateral corner; surface of the two posterior palp rugose with many pustules; anterior palp of the three at posterolateral corner short and stubby; pair of stubby papillae located posteromedially between the two posterior palps. Tongue anlage broad and raised; pair of smooth long lingual papillae oriented outwards present medially on tongue anlage. BFA well defined by six pairs of BFA papillae; six long conical papillae beginning from middle of BFA, converging at posteromedial region of floor; papillae long, conical and unequal in size; third papilla largest and with a bifurcated tip; BFA with about 30 pustules concentrated at posterior end; few papillae and pustules beyond lateral sides of BFA. Buccal pockets opening narrow and transversely arranged and narrow; pre-pocket papillae absent. Few pustules in region between tongue anlage and buccal pockets. Ventral velum wide and sinuate; space between BFA and ventral velum with few pustules spread medially; ventral velum margin with 14 projections; outer three projections on either side widely placed with remaining concentrated at the centre. Median notch not prominent; outer margin granular with secretory pits. Glottis exposed way behind ventral velum.

Denticles ( fig. 56e ) moderately spaced between and strongly curved towards mouth at apex; sheath followed by body narrow; tip of head broadly curved; 14‒18 short and moderately curved cusps on each denticle.

Each serration ( fig. 56f ) on jaw sheath with a wide base and a triangular pointed head.

Figures

Figure 55. Polypedates cf. megacephalus, Gosner stage 36. External morphology: (a) Lateral view, (b) Dorsal view, (c) Ventral view. Scale = 10 mm.

Figure 56. Polypedates cf. megacephalus, Gosner stage 34. Buccopharyngeal and denticles: (a) Buccal roof, Scanning Electron Microscopy photograph, scale = 0.2 mm, (b) Buccal roof, Alcian Blue stained photograph, ventral view, scale = 1 mm, (c) Buccal floor, Scanning Electron Microscopy photograph, scale = 0.2 mm, (d) Buccal floor, Alcian Blue stained photograph, ventral view, scale = 1 mm, (e) Individual denticles, scale = 0.01 mm, (f) Jaw sheath serrations = 0.01 mm.