Mantidactylus betsileanus (Boulenger, 1882)

Knoll, Angelika, Köhler, Jörn, Glaw, Frank, Teschke, Meike & Vences, Miguel, 2007, Larval morphology in four species of Madagascan frogs of the subgenus Brygoomantis (Mantellidae: Mantidactylus), Zootaxa 1616, pp. 49-59 : 51-52

Mantidactylus betsileanus (Boulenger, 1882)

Series examined. ZSM 848/2004 from Andasibe (1 specimen), ZSM 876/2004 (2 specimens) and 880/2004 (10 specimens) from Fierenana, ZSM 1080/2004 (1 specimen) from Ranomafana. Tadpoles were collected from small and very shallow, slow-flowing streams. Sampling was done in January/ February 2003 and February 2004.

Taxonomic note. We here follow the definition of Mantidactylus betsileanus introduced by Blommers- Schlösser (1979). Calls of M. betsileanus were first described by Blommers-Schlösser (1979) and documented by Vences et al. (2006) on CD 2, Track 62. This species is common at Andasibe and Ranomafana (where it occurs sympatrically with M. sp. aff. betsileanus "very slow calls"), and was the only species of this complex heard at Fierenana.

Description (based on a tadpole out of the series ZSM 880/2004, field number 2003.1668; Genbank accession number EF606877 ; Fig. 1 ). Tadpole in stage 38 and in good state of preservation (tip of tail slightly deformed naturally). Colouration in preservative, tan brown, posterior body dorsally and ventrally scattered with irregular brown flecks, caudal dorsal fin covered with some fawn flecks and spots, belly, caudal muscle and ventral fin almost uniformly transparently drab. In dorsal view, body shape elliptical, head and body separated by a constriction of the body wall at the plane of the spiracle. In lateral view, body depressed, BW 1.25 of BH. Nostrils rounded, not protuberant, positioned dorsolaterally, IND 0.62 of IOD, slightly closer to the tip of the snout than to the eyes, S– N 0.77 of N–E. Eyes positioned dorsally, directed dorsolaterally, moderately sized, ED 0.10 of BL. Spiracle sinistral, visible in dorsal view, attached to the body wall but its tip lifting up from the body wall, closer to the end of the body than to the tip of the snout, S– S 0.66 of BL, spiracular opening oval, laterally positioned, oriented posteriorly, closer to venter than to dorsum. Intestinal spiral slightly visible in dorsal view, visible in lateral view, well visible in ventral view. Vent tube median, cloacal aperture dextral to caudal fin. Caudal musculature well developed, TMH 0.64 of BH and 0.60 of MTH, gradually tapering from base to the almost reached tip. Dorsal fin originating at the tail-body junction, slightly convex, point of maximum height located a bit further as midtail, MTH 1.07 of BH, margins almost parallel to caudal muscle. Oral disc of moderate size, generalized, emarginated, ODW 0.20 of BL and 0.33 of BW, anterioventrally positioned, with robust dark coloured beaks, nearly surrounded by marginal papillae. Oral disc margins not visible in dorsal view, but visible in lateral view. Keratodont row formula 1:4+4/1+1:2, about 38 keratodonts per mm. Keratodont row length reduces from A2 to A4. Upper labium with large dorsal gap, DG 0.84 of ODW, 8 marginal papillae and one submarginal papilla on each side, lower labium with two rows of papillae (app. 39 in marginal row, app. in 28 submarginal row). All papillae with a rounded tip, less than 1.0 mm in length each. Upper beak M-shaped, lower beak V-shaped, both with almost equal-sized serrations.

Measurements (in mm). BL 12.8; TAL 25.7; TL 38.5; BW 7.6; BH 6.1; ED 1.3; IOD 4.5; IND 3.9; S– N 1.7; N– E 2.2; S– S 8.4; TMH 3.9; TMW 4.3; MTH 6.5; ODW 2.5; DG 2.1.

Variation within the series. Series ZSM 880/2004 with 9 additional tadpoles in stages 25–36, some in poor state of preservation (measurements only partly included). Morphological proportions vary as follows: BW 1.09–1.33 of BH, ED 0.07–0.10 of BL, S– N 0.67 –1.00 of N–E, IND 0.54–0.75 of IOD, S–S of BL 0.53– 0.63, TMH 0.46–0.61 of BH, TMH 0.42–0.53 of MTH, MTH 0.89–1.24 of BH, ODW 0.20–0.25 of BL, ODW 0.33–0.39 of BW (see Tab. 1 ). Keratodont row formula is not consistent. Stages 25 and 26 differ from older stages by keratodont row formulae 1:3+3/1+1:2 and 1:3+3/3. In earlier stages, the skin is more transparent and the intestinal spiral is well visible in dorsal view, lying under the apex of myotomes of the tail musculature.

Stage 25 25 26 26 27 36 38 Previous descriptions. In comparison to the data provided by Blommers-Schlösser (1979) our series differs only slightly. Our tadpoles in stages 25 and 26 have maximum body lengths of 7.1 and 9.6 mm, respectively, and therefore are approximately 0.6 mm larger than tadpoles of the same stages measured by Blommers-Schlösser (1979). This also refers to the maximum recorded body length in stages 26–30, which was given as 9.0 mm by Blommers-Schlösser (1979) and is 10.3 mm in a stage 27 larva from our sample. The average ratio of tail to body length is 2.05 (range 2.0–2.1) in our sample and 2.2 according to Blommers- Schlösser (1979). See discussion.

Figures

FIGURE 1. Drawings of the preserved voucher tadpole of Mantidactylus betsileanus (stage 38), series ZSM 880 / 2004; (A) dorsal view, (B) lateral view, (C) oral disc.