Amolops assamensis (Sengupta, Hussain, Choudhury, Gogoi, Ahmed & Chaudhury, 2008)

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 : 75-77

S18. Amolops assamensis (Sengupta, Hussain, Choudhury, Gogoi, Ahmed & Chaudhury, 2008) ( fig. 37‒38 )

Larval series examined. WT 161.1510 ( Mayeng Hill Reserve Forest , Kamrup District, Assam, India). Tadpoles of this species were collected from a torrent stream at the type locality of the species. Tadpoles were found clinging to the rocky boulders in the stream using their abdominal suckers .

Notes. Tadpoles were preserved in 10 % buffered formalin, and no molecular data from the specimens was available. Tadpoles were collected in the type locality of this species and reared ex-situ for taxonomic verification.

External morphology. Description of a tadpole at Gosner stage 37. Body shape oblong (tubular), broad in its anterior part, depressed in dorsal and lateral perspectives ( fig. 37a‒b ). Body length 38 % of total length; maximum body diameter at axis of eye. Snout broadly rounded in dorsal perspective and rounded in lateral perspective. Eyes large, located dorsally and oriented dorsolaterally; distance between eye and nostril 38.9 % of distance between eye and snout. Nostril opening oblong with rim elevated, closer to eye than to snout, placed parallel to eye in dorsal view; inter-narial distance 60.7 % of inter-orbital distance; distance between nostril and snout 24.1 % of body length. Spiracle sinistral; inner wall of tube completely formed and free; tube orientation posterolateral, its opening located below the medial and above the lateral side of venter. Distance between spiracle and snout 73 % of body length. Opening of vent tube medial with a small aperture. Tail tip rounded; musculature linear until first half length of tail, tapering beyond. Dorsal fin originating at junction between body and tail, ventral fin originating at middle of tail; dorsal fin wider than ventral fin; maximum height of caudal fin at mid-length. Height of tail muscle 96 % width at tail-body junction. Tail (caudal) musculature accounting for 67 % width of tail muscle at body-tail junction. Lateral lines present but not conspicuous. Pair of glands present behind eyes on dorsal side and gular region on ventral side.

Oral disc ventrally located ( fig. 37c ). Rostral width of oral disc 66 % of maximum body width, not emarginated; not visible dorsally; single row of marginal papillae spread on lateral commissures; submarginal papillae absent; upper labium larger of both labia; ventrally, gastrozymous muscles behind oral disc transformed into a suction apparatus. Labial tooth row formula A8(4‒8)/P3(1). Order of lengths of labial tooth rows A1> A2> A3> P1> P2> P3> A4> A5> A6> A7> A8. Jaw sheaths well developed, both jaw sheaths strongly keratinized. Jaw sheath margins uniformly serrated with large serrations; supra-rostrodont longer than wide, with an indentation medially, not divided; infra-rostrodont V-shaped, with slight concavity medially.

Measurements of 15 tadpoles at various Gosner stages (25‒26, 35, 37‒38, 40) are given in tab. 17 .

Coloration. In preservation, dorsal body olive-brown. In lateral perspective, flanks comparatively darker than dorsum. Ventral integument opaque and dirty white with no melanophores. Dorsal and ventral fins transparent and spotted with tiny melanophores; tail musculature olive-brown spotted with numerous melanophores. Spiracle, oral disc and vent tube milky white with no melanophores.

Buccopharyngeal morphology. Buccal roof ( fig. 38a‒b ). Prenarial arena of roof smooth with no pustules or ridge. Internal nares parallel to one other; oriented anteromedially; gap between nares narrow, less than half the length of nare; anterior and posterior narial walls low with anterior wall slightly raised than posterior wall; both narial walls free of pustules or papillae. Postnarial arena with a pair of short pustulose papillae oriented medially. Median ridge papilla and lateral ridge papillae absent. BRA not defined and smooth; a smooth conical papilla present on lateral border on each side of roof; pustules absent in BRA. Glandular zone prominent. Dorsal velum low and discontinuous with few tiny projections on margin.

Buccal floor ( fig. 38c‒d ). Prelingual arena with three diminutive papillae at anterolateral corner and a flattened palp at posterolateral corner of jaw sheath on each side; margin of palps with few dilations. Tongue anlage prominent and oval; pair of small lingual papillae at lateral corners of tongue anlage projecting outwards. BFA not well defined and smooth; three to four short conical papillae present at posterolateral corners of the arena. Buccal pocket opening wide and transverse; region between tongue anlage and buccal pockets with two to three stubby papillae and few tiny postulations; a pustulated pre-pocket papilla oriented anteriorly. Ventral velum smooth with about eight projections concentrated at the centre. Median notch prominent; margin of velum smooth. Glottis exposed posterior to ventral velum.

Denticles ( fig. 38e ) closely packed and moderately curved towards mouth at apex. Oral angle straight with apex slightly curved; sheath and body of equal width; head uniformly broad with 28‒32 short and moderately curved cusps.

Each serration ( fig. 38f ) on jaw sheath with a wide base and a rounded head, and a pointed tip.

Figures

Figure 37. Amolops assamensis, Gosner stage 37. External morphology: (a) Lateral view, (b) Dorsal view, (c) Ventral view. Scale = 10 mm.

Figure 38. Amolops assamensis, Gosner stage 37. 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 = 0.1 mm.