Leptodactylus vastus A. Lutz, 1930

Description of the tadpoles of Leptodactylus vastus A. Lutz, 1930 View in CoL

External morphology — Tadpoles at Gosner stage 37 have globular bodies that are slightly compressed in lateral view, ovoid in a dorsal view, and wider than high ( Fig. 1 View FIGURE 1 ). The body length is about 30% of the total length; the snout is short, rounded in dorsal and lateral view, eyes large, dorsolateral, with diameters about 12% of the body length, interglobal distance 31% the width of the body; eye-snout distance is about 16% of the body length, and eye-nostril distance represents 10% of the body length. Tadpoles of L. vastus in more advanced developmental stages have similar total length (stages 38 with 52 mm, 39 with 52.5 mm, and 40 with 52 mm).

Nostrils small, rounded, with internarial distance about 31% of the body length, with nostrils dorsally positioned, half way the distance between the eyes and the snout. Internarial distance greater than eye-nare distance. Spiracle short, sinistral, fused to the body and located laterally at the middle third of the body, with the circular opening dorsally oriented.

Tail with visible musculature, large base, rounded extremities about 72% of the total length. Cloacal tube median, short, and fused to the tail; dorsal fin higher than ventral fin, with its greatest height at the middle of the tail. Ventral fin thin and not arched.

Oral disk — Oral disk almost anteriorly placed ( Fig. 1A View FIGURE 1 ), not emarginate, about 29% of the body width, surrounded by marginal papillae interrupted by a rostral gap. Marginal papillae are arranged in a double row on the upper lip, a single row in the lateral region, and then again a double row in the lateroventral and ventral regions of the oral disk. In the mid-ventral region of the oral disk there is a small interruption in the rows of marginal papillae. Submarginal papillae appear in the commissural area ( Fig. 2A View FIGURE 2 ). Papillae long, conical, simple and rounded.

Most of the tadpoles examined (75%) showed a 1/2(1) LRTF, whereas 25% of the individuals had a 1/3(1) LRTF. The P-1 row is slightly interrupted medially, and the P-2 row is shorter than the others ( Fig. 2A View FIGURE 2 ). P-3, when present, about a third of P-2 length. Keratodonts dark, with three distinct zone: base, neck and head; head slightly convex, with 7–9 cusps laterally arranged ( Fig. 2B View FIGURE 2 ). Upper and lower jaw sheaths intensely pigmented and serrated; upper sheath V-shaped and lower sheath slightly convex.

Coloration — In life, the dorsal region of the tadpoles has a light-brown color, with gray to olive-green tones, and dark-brown splotches; flanks the same color as the dorsal region; spiracle transparent, anterior third of belly whitish and posterior region transparent, being possible to distinguish the internal organs. Dorsal and ventral fins slightly pigmented, with splotches with essentially the same coloration as the dorsal region; muscular portion of the tail fin with dorsal region more heavily pigmented than the ventral region.

When preserved in formalin, tadpoles show a dark-brown dorsal region with irregularly scattered black blotches; the flanks are of the same color as the dorsal region and the ventral area is transparent. The dorsal and ventral fins are transparent, with few dark blotches; the muscular portion of the tail is scarcely pigmented, with small blotches of the same color as the dorsal region. Tadpole measurements are listed in Table 1 View TABLE 1 .

Internal Oral Anatomy — Buccal floor triangular and wide ( Fig. 3A View FIGURE 3 ). Oral opening about 12% of the buccal floor width. Two pairs of infralabial papillae: anterior pair conical, taller than wide, slightly obliquely oriented, with acute tip and margins without pustulations. The posterior par is wide than taller, oriented transversally in relation to the buccal opening, with rounded apices and margins with postulations.

Four simple, conical lingual papillae with acute tips; 4–5 short, conical prepocket papillae and 14–18 prepocket pustulations. Buccal floor arena (BFA) circular, with eight long papillae and 12–14 smaller papillae on each side, all conical and with acute apices. The medial region of the BFA shows 70–76 uniformly spaced pustulations, and 17–20 small papillae among them. Buccal pocket longer than wide, transversally oriented on the medial region of the buccal floor. Velar surface free, long, and with small marginal projections.

Pharyngeal cavity with slightly oval branchial baskets longer than wide, both with surface areas of about 27% of the total area of the buccal floor. Third filter plate slightly wider than the second plate, imbricate, covering 1/2 of the fourth plate. Filter mesh dense, with tertiary and higher order folds present. Filter rows moderately wide, intermittently abutting, but with filter canals exposed, corresponding to approximately 1/3 of the width of these filter rows. Glottis small and tall, with moderately thick lips. The measurements of the anatomy feature of pharyngeal cavity are listed in Table 1 View TABLE 1 .

Buccal roof slightly triangular, narrow in the prenarinal arena and caudally wider ( Fig. 3B View FIGURE 3 ). A transversal V-shaped ridge is present in the prenarial arena, anterior to the internal nares. Internal nares longer than wide, obliquely oriented, positioned about 31% of the distance between the oral disk and the esophagus. Anterior portion of each nare without pustulations; posterior portion with an indistinct narial valve. Postnarial arena narrow with two large papillae with rounded, pustulated tips, and 6–8 pustulations between them ( Fig. 3B View FIGURE 3 ). Median ridge wide with trapezoidal shape and with 3–5 pustulations on the free external surface. Lateral ridge papillae simple, conical, with acute apices, transversally oriented on each side of the median ridge and with small pustulations on the anterior edge. Near the lateral papillae ridge there appear 5–8 postnarial pustulations. Buccal roof arena (BRA) poorly defined, with two long papillae and 4–6 shorter papillae, all conical with acute apices; 30–40 pustulations uniformly arranged. Glandular zone poorly defined, with small pustulations. Dorsal velum long, gradually curving, interrupted medially and with free edges with no pustulations.

Habitat — Calling adult frogs, eggs, and tadpoles were observed in a temporary pond within the study area early on the rainy season. Eggs in a foam nest (n = 4) were observed in cavities excavated by the males at the edge of a temporary pond, being separated one from another by 0.45–2.30 m.

The tadpoles of Leptodactylus vastus are predominantly nocturnal, benthic, possess a cryptic coloration, and remain in the foam nest until water fills the small excavations and allows the tadpoles to reach the temporary pond itself. The tadpoles do not exhibit schooling behaviour, and react immediately to potential predators by swimming rapidly away for short distances.