Sphaenorhynchus lacteus

External Morphology. Description based on one tadpole at Stage 32 (LCS s/n). Because this was a single, unidentified but clearly unknown tadpole, the tadpole was photographed (Fig. 48A) and reared through metamorphosis (Fig. 48B). The tadpole was described alive and thus not all characters employed in the characterization of other species could be recorded. A summarized description follows. Total length 22.6 mm. Body elongated oval in dorsal view and depressed in lateral view. Snout rounded in dorsal view. Eyes small, located and directed laterally. Nostrils oval, with opening anterolaterally directed. Oral disc anteroventral, non-emarginate; marginal papillae uniseriate, with a wide a dorsal gap. Marginal papillae of variable sizes. Submarginal papillae absent. LTRF 2(2)/3. Jaw sheaths narrow, finely serrated; anterior jaw sheath shaped as a flat arch, posterior jaw sheath U-shaped. Spiracle single, sinistral, conical, posterodorsally directed. Vent tube large, wide, medial, with a medial opening. Caudal musculature of moderate width; in lateral view gradually tapering to a pointed tip. Dorsal fin moderately high, originating at the tail-body junction, convex; ventral fin moderately high, convex. Tail tip rounded.

Colour. In life body olive brown with golden flecks on the sides; dorsal and ventral thirds of eyes golden, medial third red; fins translucent with a marbled brown pattern and scattered golden chromatophores (Fig. 48A).

Metamorphs. Metamorphs green with yellow reflections in head, dorsum and legs (Fig. 48B).

Natural history. Eggs were not observed in Central Amazonia. Gravid females contain on average 478 ovarian eggs (Ĥdl 1990). Tadpoles are found in floating meadows in várzea floodplain lakes.

Comments. Tadpoles of S. lacteus were described by Duellman (2005) from Peru and by Lynch & SuárezMayorga (2011) from Colombia. Tadpoles of Peru differ from those herein characterized by presenting eyes large, ventral tube dextral, LRTF 2 (2)/3(1), dorsal fin originating on the proximal caudal musculature (although his Fig. 13.8E shows dorsal fin originating at the tail-body junction), slender tail tip, posterior jaw sheath broadly V-shaped. Tadpoles from Colombia differ from those herein characterized by presenting LTRF 2 (2)/3(1).

Genus Trachycephalus. Tadpoles of genus Trachycephalus found in the Central Amazonia share the following combination of morphological characteristics: moderate size; body elongate oval in dorsal view and triangular in lateral view; dorsal fin of moderate height or high; oral disc anteroventral, ventrolaterally emarginate; marginal papillae biseriate with a dorsal gap; submarginal papillae present.