Mantidactylus majori, Boulenger, 1896

dos Santos Dias, Pedro Henrique, Vera Candioti, Florencia, Wassersug, Richard, Lukas, Paul, Targino, Mariane, Glos, Julian, Wheeler, Ward C, Hertwig, Stefan, Crottini, Angelica & Haas, Alexander, 2024, Stranger things: on the novel buccopharyngeal anatomy and functional morphology of ‘ sand-eating’ Malagasy tadpoles (Anura: Mantellidae: Mantidactylus), Zoological Journal of the Linnean Society 202 (2), pp. 1-13 : 4-5

Mantidactylus majori

Oral disc: Oral configuration is described and illustrated in Randrianiaina et al. (2011a) and reproduced here ( Fig. 1 ). SEM micrographs show slight flaking of a keratinized epithelium on the surface of the three, large, thorn-like papillae in the normal position of the upper jaw sheath ( Fig. 5A, B ); lower jaw sheath U-shaped, slightly keratinized, and marginally smooth ( Fig. 5D ).

B uccalfloor ( Fig.5D, E ): Fivepairsoftall, conicalinfra-labialpapillae aligned on the posterior margin of Meckel’s cartilage. Tongue anlage with one pair of tall, flat, lingual papillae with pustulated tips. Buccal floor arena delimited by two long, thick crests formed of about 20 transverse ruffled ridges closely spaced (365–375 µm long, 40–200 µm wide; detail in Fig. 5E ); crests meet medially thus forming a horse-shoe intricate margin surrounding the whole buccal floor arena. Central region of the arena smooth, except a medial, posterior area where several scattered short, pustulated papillae appear. Buccal pockets oriented transversely. Ventral velum without marginal projections and median notch. Glottis fully covered.

Buccal roof ( Fig. 5F, G ): Prenarial arena with a wide inverted-V crest with smooth margin. Internal nares large and slit-like, transversely oriented; margins thick and mostly smooth, with a long, conical papilla at the anterolateral edge, projecting posteriorly. Median ridge rectangular, taller than wide, and with crenulated free margin. Buccal roof arena entirely ornamented with c. 22 bilateral, transverse, parallel ruffled ridges of densely packed, short papillae; posteriorly to the median ridge, these ridges meet medially with the contralateral one and papillae appear less packed; some larger papillae are scattered along the midline; laterally, each ridge ends in a hand-like flap papilla that recurves medially (detail in Fig. 5G ); these flaps are large in the middle section, and gradually decrease in size rostral and caudally. Overall, ridges are 400–830 µm long and 90–160 µm wide, and cover about 45% of the buccal roof. Threedimensional reconstruction of the buccal cavity ( Fig. 5C ) shows how buccal roof and floor structures align relative to each other, with dorsal crests fitting exactly within the space defined by ventral crests. Unfortunately, the dorsal velum was broken in SEM images.

Figures

Figure 1. Oral discs of Mantidactylus tadpoles examined. Adapted from Randrianiaina et al.(2011a). Note the extraordinary diversity of oral discs, from configurations similar to pond-type tadpoles in M.argenteus (with keratinized jaw sheaths and labial tooth ridges) to the highly derived morphologies in M. mocquardi and M.majori, with minimum keratinization and extensive papillation. Scale bars: 1 mm. Reprinted with permission of the Journal "Contributions to Zoology".

Figure 5. Oral disc and buccopharyngeal morphology of Mantidactylus majori (ZSM 042/2007 for oral disc and ZSM 1684/2004 Stage 29 the remaining).A, upper lip, showing three large papillae in the place of upper jaw sheath. B, detail of the central papillae, showing a likely slight keratinization of the surface, as suggested by tissue flaking.C, three-dimensional reconstruction of a CT scanned specimen, showing the arrangement of dorsal (yellow, central region) and ventral (cream, lateral regions) ruffled ridges regarding the chondrocranium:ventral view of the chondrocranium, transverse section at the level of subocular fenestrae, and sagittal section at midline; in the latter image, the hyobranchial apparatus was not removed to show the tight space between buccal roof and floor that crowded ruffled ridges occupy; arrows indicate anterior. D, buccal floor; note the extraordinary development of the ruffled ridges, and the bilateral crests meeting medially forming a horse-shoe structure. E, detail of ventral ruffled ridges from the anterior section of the right crest; note the rows of tall, cauliflower-like papillae packed together forming each ridge.F, buccal roof; note the transverse, bilateral ruffled ridges occupying the entire buccal roof arena. G, detail of dorsal ruffled ridges from the mid portion of the left crest; note the lateral edge of each ridge retaining a papilla- or flap-like aspect and the medial portion proliferating with a cauliflower-like appearance as in the buccal floor. Scale bars: 500 µm (A, D, F), 100 µm (B, E, G).