Comprehensive DescriptionRead full entry
Sphaenorhynchus lacteus is a relatively large Sphaenorhynchus (Lime Treefrog) found in South America. Snout-vent length is 25.5-41.5 mm in males, 38.4-45.7 mm in females (Duellman 2005). The skin is smooth dorsally, granular ventrally. The snout is pointed when viewed from above, and angles sharply back when viewed laterally. The pupil is horizontally elliptical (Benício et al. 2011). A dark canthal stripe often runs from the anterior corner of the eyes to the tip of the snout. The vomerine teeth are arranged in oval patches between the rear portions of the choanae. The tympana are exposed, and a tarsal fold is present. Fingers are approximately two-thirds webbed, while toes are completely webbed (Rivero 1969).
Sphaenorhynchus lacteus can be distinguished from other Sphaenorhynchus species by its large size, well-defined canthal stripe, more extensive webbing of the digits, and lack of a dorsolateral stripe (Rivero 1969).
In life the dorsum of S. lacteus is green. The canthal stripe is dark brown. The eyes are a creamy bronze color. White ventrally, and along the outer margins of the limbs. The limbs are a bluish green viewed from below (Benício et al. 2011).
Males tend to be smaller than females. The appearance of the canthal stripe may vary. Amount of webbing and disc size also may vary between individuals or across populations (Rivero 1969). Males have nuptial pads on the thumbs and a large, median, subgular vocal sac (Benício et al. 2011).
Sphaenorhynchus lacteus tadpoles are oval in shape with blunt snouts. Body length in stage 25 tadpoles is 4.1-7.2 mm, with a total length of 12-14.3 mm. At stage 42, one individual had a body length of 24.1 mm and a total length of 54.6 mm. Eyes are large and directed to the side. Oral disk is small. The musculature of the tail is moderately robust. At its maximum height, the tail fin is half the height of the caudal musculature (Duellman 2005).
Tadpoles are dark purple dorsally with silver or gold mottling on the sides. The iris is yellow. The chin is grey with flecking, while the belly is purple. The tail has purple stripes. In preservative, tadpoles appear brown and grey (Duellman 2005).
The species authority for S. lacteus is François Marie Daudin, 1803. The species was first described as both Hyla lactea and H. aurantiaca by Daudin. (Note: A "Hyla lactea" had been previously described by Josephus Nicolaus Laurenti in 1768. This species, however, had a large mouth, milky white spots, and barred flanks. This was not the same species as Daudins Hyla lactea, and thus is not the same species as S. lacteus). Hyla lactea and H. aurantiaca were then shown to be a single species in 1969 by Juan A. Rivero, who renamed the species Sphaenorhynchus eurhostus. An analysis of nomenclature by William E. Duellman and John D. Lynch in 1981 found that the species would most accurately be called Sphaenorhynchus lacteus (Duellman and Lynch 1981).
Its common name in Spanish is "Rana Fantasma" (La Marca et al. 2010), which translates to "Ghost Frog."