Mantidactylus albofrenatus, (MULLER, 1892)

Grosjean, Stéphane, STRAUss, Axel, Glos, Julian, Randrianiaina, Roger-Daniel, Ohler, Annemarie & Vences, Miguel, 2011, Morphological and ecological uniformity in the funnel-mouthed tadpoles of Malagasy litter frogs, subgenus Chonomantis, Zoological Journal of the Linnean Society 162 (1), pp. 149-183 : 153-160

MANTIDACTYLUS ALBOFRENATUS ( MÜLLER, 1892)

The tadpoles of M. albofrenatus described here are typical funnel-mouthed tadpoles as previously reported for other species of the subgenus Chonomantis ( Blommers-Schlösser, 1979) . There are no obvious diagnostic characters compared to tadpoles of other species of Chonomantis , except for some subtle details of uncertain diagnostic value that we describe in the subsequent accounts on these species, and except for M. aerumnalis and M. sp. 59, which can be distinguished by, respectively, their coloration and by the presence of rudimentary keratodonts (see the accounts on these species below).

The following description of external morphology of the tadpole of M. albofrenatus is based on the DNA voucher in stage 26, ZSM 420/2004 (field number FGMV 2002.1636; GenBank accession number GU808493 ) from Andasibe in central-eastern Madagascar (BL 9.18 mm). A second specimen from the same batch, in stage 26, is used for the description of the tail, measurements, and drawings (TL 34.1 mm, BL 9.02 mm). Buccopharyngeal features are described based on one tadpole at stage 26 out of the same series.

External morphology: In profile ( Fig. 1 ), body depressed, BW 120% of BH, snout covered by oral disc. In dorsal view ( Fig. 1 ), body elliptical, widest at middle part of intestine, snout truncate. Eyes moderately sized, ED 15% of BL, bulging, very slightly visible in ventral view, positioned dorsolaterally and directed almost laterally. Pineal ocellus not observed. Nares elliptical, of moderate size, rimmed, positioned dorsolaterally and directed anterolaterally, aperture directed slightly ventrolaterally, closer to snout than to pupils, RN 48% of NP, NN 56% of PP. Spiracle sinistral, flat tubular, relatively small, ventrolateral, attached to body wall except tip, orientated posteriorly, situated at mid-distance between tip of snout and end of body, SS 49% of BL; spiracular opening oval, directed laterally, at level of lower part of caudal muscle. Tail musculature moderately strong, TMH 76% of BH and 73% of MTH, TMW 66% of BW, gradually tapering, reaching tail tip. Tail fins moderately shallow, UF 27% of MTH, LF 24% of MTH, upper fin not extending onto body, shallow and increasing gently in size in proximal third, SU 184% of BL, increasing abruptly at first third, then following caudal muscle; lower fin straight, then curved at its end to form tip of tail; tail long, TAL 285% of BL, its point of maximum height located at proximal third, MTH 104% of BH, tail tip finely rounded. Anal tube moderately sized, dextral, tubular, directed posteriorly, linked to ventral tail fin except its free distal quarter, opening dextral with a straight edge. Lateral line organs present on snout and until before eyes, no glands visible.

Oral disc ( Fig. 2 ) umbelliform, terminal, and orientated dorsally, emarginated, thus separating upper and lower labia ‘high’ on oral disc, large, ODW 43% of BL and 70% of BW. Lower labium big, with a median notch on half its length; upper labium as two small lateral extensions, absent on median half. Inner edge lined by tiny papillae, inner side of lower labium bearing more or less rounded ridges reminiscent of papillae, a horizontal row of papillae on bottom in front of mouth opening, a large and round structure on midline just behind median notch, an elongate ‘papilla’ laterally on each side orientated anterolaterally; each part of upper labium bearing a dorsoventrally orientated ridge. No keratodonts. Jaw sheaths soft, not keratinized, very finely serrated (serrations of lower beak elongate); upper jaw sheath wide, flat and shallow, white with grey serrations; lower jaw sheath V-shaped, white with black serrations.

Coloration in preservative: Upper side translucent (internal organs slightly visible) sprinkled with small orange-brown blotches, especially on snout. Upper part of flanks similar to back, with orange-brown blotches on posterior part. Lower part of flanks unpatterned. Ventral side and lower part of caudal muscle unpatterned, internal organs visible through skin. Upper part of caudal muscle unpatterned on its largest part but coloration of lateral parts invades it resulting in an irregular banding pattern. Lateral parts with irregular light orange-brown blotches (much darker in the interface muscle/upper fin). Dorsal fin bearing these blotches, especially on proximal half, ventral fin unpatterned. Some ridges of oral disc brown.

Variation: The ratios taken for three other tadpoles at stage 26 (from the same series, ZSM 420/2004; TL 30.0– 32.3 mm, BL 7.7–9.2 mm, no TL value available for the largest specimen) vary in the following proportions: BW 115–125% of BH; ED 15–16% of BL; RN 46–55% of NP; NN 61–62% of PP; SS 46–51% of BL; TMH 76–85% of BH; TMH 72–76% of MTH; TMW 60–65% of BW; UF 27–28% of MTH; LF 25% of MTH; SU 143–184% of BL; TAL 273–284% of BL; MTH 106–112% of BH; ODW 40–46% of BL; ODW 71–74% of BW.

Buccal floor ( Fig. 3 ): Prelingual arena trapezoidal, two vertical ridges on inner side of lower beak; two pairs of small and simple prelingual papillae on same horizontal plane lying on lateral wall of arena, directed medially. Tongue anlage prominent, elongate transversally and curved backwards; one pair of relatively long and simple lingual papillae posterodorsally orientated. Buccal floor arena triangular, delimited by a row of 11–12 stocky and very small papillae on each side, the biggest one in front of buccal pocket bearing two or three stubs, two posterior-most finest and orientated anterolaterally; interior of arena with some scarce and faint pustules. Buccal pockets narrow, curved, and almost obliquely orientated; a longitudinal row of six to eight prepocket papillae in continuity with buccal floor arena papillae almost reaching level of posterior end of tongue anlage. Ventral velum with spicular support, bearing a blunt triangular projection above third filter plate, a very flat and large projection above second filter plate and four fine projections above first filter plate; no medial notch; glottis covered by velum except for its posterior end; no secretory pits visible. Branchial baskets wider than long, curved dorsally; with three filter cavities, filter plates obliquely arranged, filter mesh with main folds and some secondary folds.

tated. Choanae moderately sized, transverse; anterior wall slightly elevated, smooth, bearing a simple fine and long papilla on lateral half; narial valve slightly elevated, forming a rounded flap wrapping medial extremity of choana with a ventrally orientated prominence at its extremity. A large, flat, and rounded flap behind each choana on a prominence, probably homologous to postnarial papilla. Postnarial arena without ornamentation. Median ridge arrow-like pointing posteriorly. No lateral ridge papillae. Buccal roof arena diamond-shaped; two tiny buccal roof arena papillae on each side, biggest anterior; interior of arena with faint pustules. Posterolateral ridge present and prominent, raised, not continuous across dorsal roof. Glandular zone present, absent medially, with relatively large secretory pits. Dorsal velum continuous through dorsal roof, elevated laterally. Pressure cushions not evident, maybe damaged during dissection.

Buccal roof ( Fig. 4 ): Prenarial arena rectangular, two vertical ridges on anterior wall following upper beak; one pair of flat and roughly oval prenarial papillae at posterior end of ridges, ventrally orien-

Figures

Figure 1. Lateral and dorsal views of tadpoles of Mantidactylus belonging to the subgenus Chonomantis. Mantidactylus albofrenatus, specimen in stage 26 from the batch ZSM 420/2004. Mantidactylus brevipalmatus, specimen ZMA 7078 in stage 28. Mantidactylus delormei, specimen ZSM 440/2004 in stage 40 (coloration of specimen largely faded and therefore only outline drawn). Mantidactylus melanopleura, specimen ZSM 1318/2007 in stage 26. Mantidactylus opiparis, a specimen from the batch ZSM 416/2004 in stage 25. Mantidactylus zipperi, specimen ZSM 1825/2007 in stage 35. Mantidactylus sp. 59, specimen ZSM 707/2007 in stage 27. Scale bars = 10 mm.

Figure 2. Oral discs of tadpoles of Mantidactylus belonging to the subgenus Chonomantis. Mantidactylus albofrenatus, specimen in stage 26 from the batch ZSM 420/ 2004. Mantidactylus brevipalmatus, specimen ZMA 7080 in stage 27. Mantidactylus delormei, specimen ZSM 440/ 2004 in stage 40. Mantidactylus melanopleura, specimen ZSM 415/2004 in stage 25. Mantidactylus opiparis, specimen from the batch ZSM 416/2004 in stage 25. Mantidactylus zipperi, specimen ZSM 1821/2007 in stage 39. Mantidactylus sp. 59, specimen ZSM 707/2007 in stage 27. Note that the oral disc of M. sp. 59 is drawn in frontal view (all other drawings in dorsal view), and that it contains a row with a low number of keratodont-like structures. Scale bars = 1 mm.

Figure 3. Scanning electron microscopic pictures of buccal floor in tadpoles of Mantidactylus belonging to the subgenus Chonomantis. Mantidactylus albofrenatus, a specimen in stage 26 from the batch ZSM 420/2004. Mantidactylus brevipalmatus, specimen ZMA 6991 in stage 36. Mantidactylus zipperi, specimen ZSM 1824/2007 in stage 40. Mantidactylus sp. 59, specimen ZSM 1079/2007 in stage 27. Mantidactylus delormei, specimen ZSM 446/2004 in stage 36. Mantidactylus melanopleura, specimen ZSM 461/2004 in stage 38. Mantidactylus opiparis, specimen ZSM 422/2004 in stage 25. Scale bars = 1 mm.

Figure 4. Scanning electron microscopic pictures of buccal roof in tadpoles of Mantidactylus belonging to the subgenus Chonomantis. Specimens and stages as in Figure 3. Scale bars = 1 mm.