Description
Males of this large species of Hyloxalus attain a snout-vent length of 30.0 mm and females, 33.0 mm. The discs on the fingers and toes are expanded, half again width of the penultimate phalanges. Finger I is shorter than Finger II, and Finger III is not swollen in males. Lateral fringes are present as narrow ridges on the fingers and toes. The inner tarsal fold weak or absent and a tarsal tubercle is absent; the toes are about one-half webbed. The dorsum of the head and body is dull brown to nearly black, usually with darker brown or black irregular marks; the flanks are black. The dorsolateral stripes originate on the snout and extend to the paracloacal area; they are curved slightly medially at about midlength of the body and variable in color from nearly red to most commonly orange or to tan. The oblique lateral stripes are cream, pale orange, or most commonly bluish white; ventrolateral stripes are absent.. The upper lips and proximal dorsal surfaces of the upper arms are creamy tan to pale yellow. The dorsal surfaces of the hind limbs are tan to pale bluish gray with dark brown transverse bars or, less commonly, irregular marks; the anterior and posterior surfaces of the thighs and ventral surfaces of the limbs are bluish gray. The digital scutes are white to pale gray; the throat and belly are white to pale yellow, and the iris is reddish copper. A median lingual process is absent, and the testes are black (Frost 1986).

A tadpole in Stage 37 has a body length of 9.2 mm and a total length of 30.5. The body is ovoid and wider than high. The snout is bluntly rounded in dorsal view and rounded in profile. The large eyes are situated and directed dorsolaterally and are not visible from below. The spiracle is sinistral with a short tube attached to the body for its entire length; the spiracular opening is directed posterodorsally well below the midline at about two-thirds of the length of the body. The cloacal tube is short, dextral, and attached to the ventral fin. The caudal musculature is robust, about equal in height on the proximal third of the tail, and gradually diminishes to a pointed terminus. The dorsal fin originates on the base of the caudal musculature, attains its greatest height at midlength of the tail, and gradually diminishes to an acutely rounded tip. The ventral fin originates on the body wall and is about equal in height throughout its length. The oral disc is directed anteroventrally; the median two-thirds of the anterior labium is bare, and elsewhere the labia have a single row of subconical marginal papillae. A few small, rounded papillae are present in the shallow, lateral labial folds.. The jaw sheaths are moderately slender and coarsely serrate; the anterior sheath forms a broad arch, and the posterior sheath is broadly V-shaped. The labial tooth row formula is 2(1)/3; the anterior rows are slightly longer than the posterior rows. The body is dark brown with tan dorsolateral stripes in the largest individuals; the tail is tan with brown flecks.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Ecuador, Peru

View distribution map in BerkeleyMapper.

This species is widely distributed at elevations of 360–1500 m in the western fringe of the Amazon Basin and lower Andean slopes in southern Ecuador and northern Peru; it also occurs at elevations of 325 and 520 m on the western slope of the northern part of the Cordillera Central in northern Peru. Most individuals are active by day along rocky streams, but some have been on boulders in streams at night. One juvenile and one adult male carrying tadpoles were on leaves in the spray zone of a waterfall at night; another male carrying tadpoles was on a rock in a stream by day. Free-swimming tadpoles were in pools in streams. Near Tarapoto, Peru, this species was found sympatrically with Hyloxalus ornatus

Life History, Abundance, Activity, and Special Behaviors
Males transport tadpoles.

References

Coloma, L. A. (1995). Ecuadorian Frogs of the Genus Colostethus (Anura: Dendrobatidae). Museum of Natural History, University of Kansas, Lawrence, Kansas.

Duellman, W. E. (2004). ''Frogs of the genus Colostethus (Anura; Dendrobatidae) in the Andes of northern Peru.'' Scientific Papers of the Natural History Museum, University of Kansas, 35, 1-49.

Frost, D. R. (1986). ''A new Colostethus (Anura: Dendrobatidae) from Ecuador.'' Proceedings of the Biological Society of Washington, 99, 214-217.

Species Account Citation: AmphibiaWeb 2007 Hyloxalus nexipus <https://amphibiaweb.org/species/1590> University of California, Berkeley, CA, USA. Accessed Jan 13, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 13 Jan 2025.

AmphibiaWeb's policy on data use.