Mantidactylus aerumnalis, (PERACCA, 1893)

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 : 160-163

MANTIDACTYLUS AERUMNALIS ( PERACCA, 1893)

The tadpoles of M. aerumnalis can be distinguished from those of all other species of Chonomantis by their coloration, with a distinct dark-light pattern of large roughly transversal markings and bands on body and tail. Other morphological characters are extremely similar to all other species except for some subtle details of uncertain diagnostic value that we describe in the accounts on these species, and except for M. sp. 59, which can be distinguished by the presence of rudimentary keratodonts.

The description of external morphology of the tadpole of M. aerumnalis is based on one specimen in stage 40, ZSM 463/2004 (field number FGMV 2002.2008; GenBank accession number GU808494 ) from An’Ala (TL 43.3 mm, BL 12.1 mm). As this description refers to a specimen from An’Ala, the locality of the neotype of the species as designated by Andreone & Gavetti (1994), it is assigned to M. aerumnalis with high certainty. On the contrary, the status of specimens from Ranomafana that are used to describe variation below is uncertain; they have been listed by Vieites et al. (2009) as confirmed candidate species Mantidactylus sp. 1 because of their high divergence from M. aerumnalis (6.3% pairwise divergence in the 16S rRNA gene) and differences in adult coloration. We here include them in a preliminary way under the name M. aerumnalis because they share diagnostic characters in adult colour (lack of frenal stripe) and larval colour (distinct transversal pattern) and were sister to each other with high support in the molecular analysis of Vieites et al. (2009).

External morphology: In profile, body depressed, BW 115% of BH; body highest and widest at middle part of intestine. Eyes moderately large, ED 17% of BL. Nares closer to snout than to pupils, RN 60% of NP, NN 49% of PP. Spiracle sinistral, slightly closer to end of body than to snout, SS 56% of BL. Tail musculature strong, TMH 67% of BH and 61% of MTH, TMW 59% of BW. Tail fins, UF 21% of MTH, LF 27% of MTH, upper fin not extending onto body, SU 116% of BL; tail moderately long, TAL 253% of BL, its maximum height located at proximal third, MTH 109% of BH. Anal tube seemingly medial with a medial opening, not attached to ventral fin, but this condition could be a consequence of advanced developmental stage 41 (vent tube reducing to finally disappearing).

Oral disc: ODW 46% of BL and 75% of BW. Lower labium very developed, bearing numerous ridges, especially at periphery.

The remaining morphological characters are very similar to those of other species of Chonomantis (see description of M. albofrenatus ).

Coloration in preservative: General coloration (including fins) orange-brown, with light areas on the back: between eyes and at level of the abdomen. Laterally, light areas are present on lateral groove of anterior part of caudal muscle, on upper part of caudal muscle at the same level (as small areas) and a few on upper fin. Ventrally, a light transversal band present on branchial area and another on posterior part of body, these bands joining together on sides of body. On hind-limbs, light areas present at each articulation.

Variation: Based on five DNA vouchers tadpoles in stages 25–29: ZSM 249/2007 (field number ZCMV 4410; GenBank accession number GU808479 ); ZSM 508/2007 (ZCMV 4511; GU808485 ); ZSM 530/2007 (ZCMV 4683; GU808487 ); ZSM 650/2007 (ZCMV 5389; GU808491 ); and ZSM 1284/2007 (ZCMV 4411; GU808480 ); TL 18.1–21.9 mm, BL 5.5–12.5 mm; no TL value available for the largest specimen; all from Ranomafana National Park. These specimens are characterized by the following morphometric ratios: BW 124–140% of BH; ED 13–17% of BL; RN 35–50% of NP; NN 54–64% of PP; SS 45–57% of BL; TMH 46–62% of BH; TMW 34–53% of BW; SU 97–115% of BL; TAL 203–220% of BL; ODW 36–38% of BL; ODW 51–60% of BW. The tissue samples for DNA purposes were taken from the tail, preventing the calculation of the ratios involving the height of the tail (MTH).

The differences of the Ranomafana specimens observed in comparison with the description of the tadpole of M. albofrenatus are as follows: widest part of body situated at level of gills; pineal ocellus present at level of anterior border of sclera; spiracle bulging but flat, orientated posterodorsally, attached to body wall except inner wall, which continues as a flap of skin after opening proper; opening just below lateral axis of tadpole, orientated posterolaterally; tail musculature moderately strong; extremity of tail missing on all specimens; upper fin shallow; tail moderately long; anal tube short, medial with its aperture medial, orientated posteroventrally; lateral line system present on snout, body, apex of myotomes of caudal muscle, and at interface upper fin/caudal muscle.

Oral disc moderately large. Papillae lining inner edge of umbelliform oral disc particularly small and numerous, other structures within oral disc (papillae and ridges) small. Upper jaw sheath a large flat arch with a median convexity, not serrated, white with brown marks, free edge brown; lower jaw sheath narrowly V-shaped, with very fine and moderately long serrations, white, serrations dark brown.

The pattern of coloration of the Ranomafana population, although similar to that of the specimen from An’Ala is described again here as it is very conspicuous on these fresh specimens ( Fig. 5A 2 /A4/A6). Upper side of body light brown with numerous darker areas. Upper side of caudal muscle with an irregular broad light brown band (characteristic of tadpoles of this subgenus) on about the proximal third surrounded by dark brown. Flanks as upper side of body but with lighter spots; background colour borders progressively on dark brown towards ventral side. Lateral line organs white, very conspicuous as distinguishing very clearly from background colour. Lower part of flanks grey-brown; two vertical wide white bands, one just behind eyes, the other one a little before end of body, continuing on ventral side as two parallel transversal bands; white points of lateral line organs forming a bridge between these two bands on flanks at level of eyes. Caudal muscle brown, turning dark grey brown towards its extremity. Three large irregular white spots on proximal third of lower part of caudal muscle, first one being in contact with body, joining more or less on ventral side of caudal muscle. Caudal fins translucent grey with a dark brown cloud at caudal muscle/fin interface, particularly on lower fin; this coloration spreading over whole tail surface in distal third. Ventral side of body brown-grey with two wide transversal white bands. Umbelliform oral disc light grey with dark brown coloration anteromedially. Anal tube dark brown anteriorly on less than its half.

Figures

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 5. Life coloration of tadpoles of six species of Mantidactylus in the subgenus Chonomantis, sampled in Ranomafana National Park in February and March 2007. Mantidactylus aerumnalis, A1/A3/A5: ZSM 249/2007 lateral/ ventral/dorsal, A2/A4/A6: ZSM 505/2007 lateral/ventral/dorsal; Mantidactylus delormei, B1: ZSM 1410/2007 dorsal; Mantidactylus melanopleura, C1/C4: ZSM 837/2007 lateral/ dorsal, C2: ZSM 1141/2007 lateral, C3: ZSM 1318/2007 lateral, C5: ZSM 1123/2007 dorsal, C6: ZSM 685/2007 dorsal, C7: ZSM 652/2007 dorsal; Mantidactylus sp. 59, D1/D3: ZSM 797/2007 lateral/dorsal, D2/D4: ZSM 1208/2007 lateral/dorsal; Mantidactylus sp. 13, E1: ZSM 70/2008 lateral, E2: ZSM 74/2008 dorsal. Mantidactylus opiparis, F1/F4: ZSM 706/2007 lateral/dorsal, F2/F5: ZSM 797/2007 lateral/dorsal, F3/F6: ZSM 118/2007 lateral/dorsal, F7: ZSM 622/2007 dorsal. Scale bars = 10 mm.