Description
Atelopus onorei is a moderately sized Harlequin frog with male snout-vent lengths ranging from 35.2 mm – 41.3 mm and larger females with a snout-vent length ranges of 41.9 mm – 47.0 mm. Individuals of this species generally have a head that is approximately as long as it is wide, with male head widths ranging from 10.2 - 12.6 mm (an average of 11.6 ± 0.8 mm). The range for head lengths in males is 10.9 - 13.3 mm, the average being 12.2 ± 0.08 mm. Females are again larger with a range in head length being 12.6 – 13.6 mm (an average of 13.1 ± 0.4 mm) and head width ranging from 11.9 - 13.5 mm (an average of 12.4 ± 0.6 mm). The snout tapers to a point and protrudes a little past the lower jaw. A distinct characteristic of this species is that it lacks a tympanum membrane and annulus. Atelopus onorei generally have a smooth texture along their dorsal, chest, belly, and underside of their flanks. The skin on the throat, lateral to their cloaca, and along the flanks is typically rugose. This frog has distinct, rounded pads at the end of it digits. There is no basal webbing or lateral fringing on the hands, however webbing is present in the hind feet. The specific formula for the foot webbing of A. onorei is I1 — 1II1 — 2III2 — 3IV3 — 2V. The relative length of the fingers is II < III < V < IV, while the relative toe length is I < II < III = V < IV. Vocal slits are present in males and male A. onorei have keratinized nuptial pads on their dorsal and inner thumbs (Coloma et al. 2007).

The most distinctive feature that sets A. onorei apart from the other species in the Atelopus genus is their aqua blue iris. Yellow-orange or green coloration in life makes A. onorei most similar to A. bomolochos, which it was once mistaken as. However the latter has black irises, minute black stippling on the dorsum, and larger hand and foot length in females. Atelopus onorei differes from A. guanujo by being significantly larger and not having white spiculae in life. From A. carbonerensis and A. sorianoi, A. onorei can be differentiated by having a less protuberant snout and not having a postocular crest. Male A. onorei possess vocal slits but no row of warts on the dorsolateral sides of their body that differentiates them from A. chrysocorallus and further from A. carbonerensis. Atelopus onorei is distinguishable from A. petersi by the absence of posterior flange at the anterolateral hyoid process, slightly more mineralized cartilaginous suprascapula and scattered pits absences and the latter having white digital pads on black phalanges (Coloma et al. 2007).

In life, the dorsum is yellow-orange and green with varying amounts of each color. A few individuals have a pale yellowish-brown dorsum blotched with diffused black spots and with yellow spiculae. The iris is a distinct aqua blue with black reticulations and a thin bluish-white stripe on the upper margin of the pupil. Specimens preserved in alcohol have dorsal colors that vary from yellow to grey. In a preserved sample of 70% ethanol, the dorsal and ventral parts of limbs are a creamy yellow while the tibia, fingers III and V, toes IV and V fade to a grayish (Coloma et al. 2007).

Overall, this species shows little variation within itself. The main form of variation we see in this species is sexual dimorphism with females having larger body sizes than males and females have longer and more slender limbs. Coloration patterns are generally the same between males and females with the occasional difference occurring between males (Coloma et al. 2007).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Ecuador

View distribution map in BerkeleyMapper.

Atelopus onorei is endemic to the Pacific versant of in the Azuay Basin of Cordillera Occidental of Ecuador, Azuay Province. More specifically, it is only known from the Río Chipla and another creek 1 – 2 km west of Miguir. These sites are near fast moving streams at elevations of 2500 m above sea level. It was known to occur on terrestrial and freshwater habitats along the “humid cloud montana forest” of the Andes Mountains in Ecuador. It is believed that A. onorei requires a permanent source of water, and it usually only found near running water. However, the species has not been seen since 1990 (Coloma et al. 2007, Coloma 2008).

The Azuay Basin has a mean annual rainfall of 1000 – 2000 mm and a mean annual temperature of 12 – 18^oC.

Life History, Abundance, Activity, and Special Behaviors
Specimens collected in 1990 at the type locality were found active during the day in April and with many pairs in amplexus near the margin of the Río Chipla and one of its small tributaries. Prior to 1990, the species was abundant at the type locality (Coloma et al. 2007).

A female specimen was found containing 133 eggs that were 2.14 mm in diameter (Coloma et al. 2007).

Trends and Threats
Atelopus onorei has not been seen since 1990. There have been at least four failed expeditions in an effort to relocate the species (Coloma et al. 2007). It is currently listed on the IUCN Redlist as “Critically Endangered” and “Possibly Extinct” due to an estimated loss of more than 80% of its population (Coloma 2008).

Many factors contribute to their decline including climate change, limited geographic ranges, and disease. This species also occurs in areas where climate abnormalities are common. The Chytrid fungus, Batrachochytrium dendrobatidis, is presumed to have affected A.onorei. However, researchers like Luis Coloma argue that global warming/climate change is still the number one driver for A.onorei decline. It is believed that a series of unusually warm events are correlated with major die off of A.onorei. Furthermore, A. onorei have a very small range, consisting of two streams, making them more vulnerable to extinction (Pounds and Coloma 2008, Coloma 2008).

Possible reasons for amphibian decline

Subtle changes to necessary specialized habitat
Disease
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
The species authority is: Coloma, L.A., Lötters, S. Duellman, W.E., Miranda-Leiva, A. (2007) "A taxonomic revision of Atelopus pachydermus, and description of two new (extinct?) species of Atelopus from Ecuador (Anura: Bufonidae)." Zootaxa 1557:1-32

Despite distinct morphologies, Bayesian and Maximum Likelihood analysis of the combined mitochondrial genes 16S rRNA (fragment) tRNA-Leu (complete), ND1 (complete), and tRNA-Ile (partial) could not resolve the relationships in the A. bomolochos complex, of which A. onorei is part of. There are multiple ways this genetic indistinctness could be explained. First, the complex could be a single species with large morphological variation. Secondly, the varied morphology could be result of a recent, rapid adaptation. Thirdly, the genetic markers used may not reflect the actual genetic difference. And lastly, the different species could occasionally hybridize and dilute genetic differences. Several researchers favor the second and last hypotheses (Guayasuamin et al. 2010).

Efforts to understand the phylogenetic relationships between A.onorei and other Atelopus species are also limited because material has been lost and the original description of many species do not provide accurate locality data. The controversial debate of phylogenetic relationship leaves researchers uncertain of whether similarities among the genus reflect synapomorphies, plesiomorphies or convergence evolution. It is hypothesized that the reduction in thumb length might reflect a monophyletic assemblage but many researchers are reluctant to use this characteristic as a way of identifying Atelopus species (Coloma el at. 2007, Venegas et al. 2008).

Atelopus onorei was previously allocated to an Ecuadorian population of Atelopus bomolochos. The original material of A. bomolochos was reviewed, resulting in the discovery of A. onorei (Coloma el at. 2007).

Atelopus onorei is named after the former Curator of Entomology at Pontificia Universidad Catolica del Ecuador, Giovanni Onore. His contribution to the collection of Ecuadorian frogs during the eighties were invaluable to the scientific research at PUCE and provided key data that was later used to document extinction of amphibians (Coloma et al. 2007)

At the site west of Miguir, A. onorei shares habitat with A. nanay (Coloma et al. 2007).

References

Coloma, L. A., Lötters, S., Duellman, W.E., and Miranda-Leiva, A. (2007). ''A taxonomic revision of Atelopus pachydermus, and description of two new (extinct?) species of Atelopus from Ecuador (Anura: Bufonidae).'' Zootaxa, 1557, 1-32.

Coloma, L.A. (2008). Atelopus onorei. The IUCN Red List of Threatened Species 2008: e.T136173A4254841. http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T136173A4254841.en. Downloaded on 27 March 2017.

Guayasamin, J. M., Bonaccorso, E., Duellman, W. E., and Coloma, L. A. (2010). ''Genetic differentiation in the nearly extinct harlequin frogs (Bufonidae: Atelopus), with emphasis on the Andean Atelopus ignescens and A. bomolochos species complexes.'' Zootaxa , 2574, 55-68.

Pounds, J.A., Coloma, L.A. (2008) ''Beware the lone killer.'' Nature Reports Climate Change 2008: 57-59. doi:10.1038/climate.2008.37

Venegas, P., Catenazzi, A., Siu-Tang, K., and Carillo, J. (2008). ''Two new harlequin frogs (Anura: Atelopus) from the Andes of northern Peru.'' Salamandra, 44, 163-176.

Species Account Citation: AmphibiaWeb 2023 Atelopus onorei: Onore's Harlequin Frog <https://amphibiaweb.org/species/6969> University of California, Berkeley, CA, USA. Accessed Nov 16, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 16 Nov 2024.

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