Osteocephalus taurinus, Steindachner, 1862

Schiesari, Luis, Rossa-Feres, Denise De Cerqueira, Menin, Marcelo & Hödl, Walter, 2022, Tadpoles of Central Amazonia (Amphibia: Anura), Zootaxa 5223 (1), pp. 1-149 : 63-65

Osteocephalus taurinus

External morphology. Description based on three tadpoles at Stage 37 (LCS 545). Total length 32.8 ± 2.1 mm (N = 3). Body ovoid in dorsal view and globular in lateral view ( Fig. 35A, B ). Snout truncate in dorsal view and rounded in lateral view. Eyes medium-sized, dorsally positioned and laterally directed. Nostrils small, oval, dorsolaterally positioned, near to eyes, with opening anterolaterally directed, without a projection on the marginal rim. Oral disc ( Fig. 35C ) anteroventral, ventrolaterally emarginate; marginal papillae conical, uniseriate, with a dorsal gap. Submarginal papillae present laterally. LTRF 2(2)/7(1); A1 and A2 of the same length; P1 shorter than P2; P3 to P6 similar in length and smaller than P2; P7 shorter. Anterior jaw sheath moderately wide and posterior jaw sheat narrow, both finely serrated; anterior jaw sheath arch-shaped, posterior jaw sheath V-shaped. Spiracle single, sinistral, conical, short and wide, posterodorsally directed, opening in the medial third of the body, with the centripetal wall fused to the body wall and longer than the external wall. Vent tube medial, fused to the ventral fin, with a dextral opening. Caudal musculature of moderate width; in lateral view gradually tapering to a pointed tip. Dorsal fin shallow and convex, originating at the tail-body junction; ventral fin shallow, convex. Tail tip pointed. Lateral lines visible.

Colour. In preservative dorsum grayish brown; caudal musculature cream and fins translucent, both with diffuse pigmentation. In life body transparent olive to brown with scattered white and/or black chromatophores; tail transparent (see Fig. 72D, E ) (Hero 1990; this study).

Variation. LTRF 2(2)/3, 2(2)/4, 2(2)/5, 2(2)/5(1) between Stages 25 and 28.

Metamorphs. dorsal and lateral surfaces grey except for a black canthal stripe continuing as a supratympanic stripe posterior to eye to insertion of the arm; dorsal surfaces of upper arm and proximal half of lower arm white; an orange spot on elbow; a large white spot, capped by a smaller orange one, on heel; another orange spot on knee; finger- and toe-discs orange; iris bright red (see Fig. 72F ).

Natural history. Eggs are deposited as a floating film ( Fig. 72A–C ) containing from 1,794 to 3,154 pigmented eggs ( Gascon 1995). Tadpoles are found in all months of the year in isolated forest ponds, streamside ponds and occasionally streams in terra-firme forest and forest edge. Eggs are preyed upon by dytiscid beetle larvae (this study) and wasps ( Lacey 1979; this study). Tadpoles are preyed upon by the snake Helicops angulatus (this study) and Pipa arrabali ( Buchacher 1993) . In experiments eggs were found to be avoided by fish but consumed by adult dytiscid beetles and Pipa arrabali ( Magnusson & Hero 1991; Gascon 1992a,b). In experiments tadpoles were found to be consumed by dragonfly larvae, oophagous tadpoles, Pipa arrabali and fish ( Hero 1991; Magnusson & Hero 1991; Gascon 1992a,b). O. taurinus tadpoles are oophagous ( Hero 1991; Magnusson & Hero 1991).

Comments. Tadpoles of O. taurinus from French Guiana ( Duellman 1978) differ from those herein characterized by presenting body elongately elliptical in dorsal view, vent tube dextral, tail acutely rounded, marginal papillae biseriate, and LTRF 3/5. Tadpoles from Peru present body ovoid, snout broad and bluntly rounded, vent tube dextral and pointed tail tip ( Duellman 2005). Tadpoles from the Bolivia lowlands have vent tube medial with a dextral opening, marginal papillae row varying from uniseriate to biseriate anterolaterally, laterally and posteriorly ( Schulze et al. 2015). Tadpoles from Central Amazonia were illustrated by Hero (1990) and described in detail by Schiesari et al. (1996). Tadpoles illustrated by Hero (1990) differ from those herein characterized by presenting papillae round, submarginal papillae lateroanteriorly and lateroposteriorly, P5 ad P6 shorter than the anterior tooth rows, spiracle posteriorly directed, and tail tip narrow. Those described by Schiesari et al. (1996) differ from those herein characterized by presenting a uniseriate row of papillae anteriorly and biseriate lateroventrally.

Figures

FIGURE 35. Tadpole of Osteocephalus taurinus (LCS 589) at Stage 36: (A) lateral view, (B) dorsal view (scale = 10 mm), and (C) oral disc (scale = 1 mm).

FIGURE 72. Indirect and direct development in anurans from Central Amazonia. (A) Amplectant pair of Osteocephalus taurinus in a temporary pond. (B) Eggs, (C) embryos, (D) tadpole, (E) metamorph and (F) newly metamorphosed froglet of O. taurinus. (G) Amplectant pair of Pristimantis fenestratus on the forest floor. (H) Eggs, (I, J and K) embryos at different developmental stages, and (L) newly hatched froglet of Pristimantis fenestratus. In I, J, and K the outermost, tougher egg capsule was removed to permit visualization of the developing embryo. Note the very large yolk reserve in (I) and the egg tooth in the snout of the about-to-hatch embryo in (J).