Charadrahyla juanitae (Snyder, 1972)
Rana-de Arbol de Juanita, Juanita's Earless Tree Frog
The arms and fingers are long and slender. A poorly developed axillary membrane that extends up to the mid-humerus is present and extends about a third of the length of the upper arm. There is also a ventrolateral dermal fold on the forearm that extends to the lateral aspect of the fourth finger. A transverse dermal fold may also be visible on the wrists. A low, flat, and bifid palmar tubercle is present. A moderately enlarged prepollex with weak horny nuptial excrescence is also present. The fingers end with round adhesive discs that are wider than the digits. Moderately large, subconcical subarticular tubercles are present, as is a weakly bifid distal tubercle on the fourth finger and sometimes the third finger. There are also small and subconical supernumerary tubercles that are often arranged in a single row on the proximal segments of fingers II - IV. The fingers are about 1/4 webbed with vestigial webbing between the first and second fingers (Snyder 1972, Duellman 2001).
The legs are also long and slender. When the hind limbs are adpressed at right angles, the heels overlap by 1/4th the length of the shank. When adpressed along the body, the tibotarsal articulation reaches the tip of the snout. There is a small tubercle on the heel and a distinct tarsal fold that run along the full length of the tarsus. There is no outer metatarsal tubercle, but the inner metatarsal tubercle is small, oval, and slightly visible from above. The long, slender toes have small, subconical to flattened subarticular tubercles and a few small, subconical supernumerary tubercles, which are arranged in rows on the proximal segment of the toes. The toes are about two-thirds webbed and the adhesive discs are smaller than in the fingers (Snyder 1972, Duellman 2001).
The dorsal skin is smooth while the skin on the throat, belly, and proximal ventral surfaces is granular. The skin on the throat is finer than the rest of the body. There is a single, median, subgular vocal sac. The posteroventrally-directed vent is located above the level of the mid-thigh, and has tubercles immediately around the vent along with rows of smaller tubercles above and below it. The vent has a short, vestigial sheath (Snyder 1972, Duellman 2001).
Charadrahyla juanitae adults can generally be distinguished from similar species in its range by coloration and patterning. It has irregular dark transverse bars along its legs, with the outer borders of the bars being a darker brown. In other species, such as Exerodonta bivocata, E. catracha, E. melanomma, E. perkinsi, and Plectrohyla hazelae these bars are generally more uniformly colored and either green, brown or yellow. Similarly, to C. pinorum, C. juanitae lacks a tympanum. However, the two can be differentiated by C. juanitae having a transverse fold along the wrist, a shorter axillary membrane, larger thumb disc, a sharply angular canthus, and smaller vent tuberbcles. Other hylidae found in Mexico can also be distinguished from C. juanitae by their lack of tubercles below the vent, as well as some of them having fully webbed feet (Duellman 2001).
Charadrahyla juanitae tadpoles can be distinguished from many other stream breeding tadpoles in Oaxaca by having a tooth row formula of more than 2/3 rows of keratodont teeth. Specifically, this feature distinguishes them from Charadrahyla altipotens, Hyalinobatrachium fleischmanni, Incilius occidentalis, Incilius marmoreus, Plectrohyla hazelae, Plectrohyla pentheter, Plectrohyla thorectes, Plectrohyla cembra, and Rana forreri. Additionally, Exerodonta sumichrasti, Megastomatohyla pellita, Ptychohyla leonhardschultzei, and Rana sierramadrensis all have more tooth rows. Charadrahyla juanitae can be distinguished from C. pinorum, by having a narrower gap in the second anterior tooth row, equivalent to less than 5 keradonts, and a less spotting on the tail. From Exerodonta melanomma, C. juanitae can be differentiated by the latter having a wider gap in the first posterior tooth row, equivalent to about 7 keradonts (Köhler et al. 2016).
The dorsal surface of adults has a light olive-grey to tan background color with a dark gray or brown, middorsal, saddle or hourglass-shaped mark surrounded by irregular blotches of the same color. There is a narrow white stripe along the canthus and a narrow dark brown postorbital stripe. In most specimens, a dark brown mid-dorsal line extends from the snout to the scapula, but the line may extend along the entire body. The dorsal surface of the limbs match the rest of the dorsum and are patterned with irregular transverse bars boarded by darker brown. The arms have 3 - 4 bars, while the thighs have 3 - 5 bars. The posterior portion of the thighs is grayish tan. The tubercles immediately surrounding the vent are darkly colored while transverse rows of smaller white tubercles are found above and below the vent. The flanks may have dorsal coloration or rows of dark brown spots. The ventral side of the frog is a creamy white color with a few dark speckles on the lateral portions of the throat. The iris is grayish bronze with dark reticulations. In preservative, the dorsal coloration fades to gray, the markings become a darker gray, and the ventrum becomes dull white (Snyder 1972, Duellman 2001).
In preservative, tadpoles have brown to tan bodies without notable markings. The caudal musculature is creamy tan and has brown flecks. The caudal fins are translucent and have brown flecks that are concentrated on the dorsal fin and posterior portion of the ventral fin (Snyder 1972, Duellman 2001).
Frogs from the Oaxacan population seem to be non-significantly larger and have more bold color patterns, however recently metamorphosed individuals have less distinct patterns than adults of that region. The canthus was lighter colored in some of the Oaxacan specimens and even had a distinct white line in some. The middorsal line is variable in length, but on rare occasions may be absent altogether. All of the dorsal blotches and patterns were variable in size shape and location; however the overall hourglass shape of coloration was present in all of the specimens (Snyder 1972, Duellman 2001).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
Males were observed calling from January to March, as well as in November from low vegetation near streams. The majority of the males were found in perches of leaves 40 - 120 cm off the ground, but some were found up to 2 meters off the ground. Calls are described as two to three loud, medium-pitched rattles that are repeated three to four times per minute (Duellman 2001).
Eggs are found in large, completely submerged, clumps attached to rocks, logs, or dead branches in streams. Clutches contain 57 – 82 eggs with diameters of 2.08 – 2.30 mm. Earlier stage tadpoles were collected from January to May, while later stage tadpoles were only found in May and June, suggesting that they breed in the dry season (Duellman 2001).
Charadrahyla juanitae is found in sympatry with C. altipotens, C. pinorum, Ecnomiohyla miotympanum, Megastomatohyla pellita, Plectrohyla pentheter, Plectrohyla thorectes, and Ptychohyla leonhardschultzei (Duellman 2001).
Trends and Threats
Possible reasons for amphibian decline
General habitat alteration and loss
Charadrahyla juanitae is most closely related to Charadrahyla pinorum based on adult and larval characters. They were originally classified under the genus Hyla, however they were put into the resurrected group Exerodonta after a taxonomic revision of the Hylidae family in 2005 (Faivovich et al.). In April of 2018, E. juanitae and E. pinorum were reassigned to the genus Charadrahyla based analysis from four mitochondrial genes and 12 nuclear genes that showed that Exerodonta was not monophyletic and that E. juanitae was nested within Charadrahyla (Faivovich et al. 2018).
At the time of the genus description, Charadrahyla, was composed of five species: C. altipotens, C. chaneque, C. nephila, C. taeniopus, and C. trux; this was determined by 56 transformation in the ribosomal genes as well as the nuclear and mitochondrial proteins. The genus Megastomatohyla is closely related to Charadrahyla (Faivovich 2005). By 2019, three more species were described, C. tecuani by Campbell et al. (2009), C. esperancensis by Canseco-Márquez et al. (2017), and C. sakbah by Jiménez-Arcos et al. (2019). Genetic analysis is needed to reveal the relationships within the genus.
The genus, Charadrahyla, was named in 2005 by Faivovich et al. The name is derived from the Greek word for “ravine”, “charadra”, in reference to where the frogs in this genus are found.
The species epithet, “juanitae” is in honor of Juanita Snyder, the wife of David Snyder, the researcher who first described the species. He named the species after her for her “invaluable assistance in the field on many expeditions” (Snyder 1972).
Campbell, J. A., Blancas-Hernández, J. C., Smith, E. N. (2009). ''A new species of stream-breeding treefrog of the genus Charadrahyla (Hylidae) from the Sierra Madre del Sur of Guerrero, Mexico.'' Copeia, 2009(2), 287-295. [link]
Canseco-Márquez, L., Ramírez-González, C.G., González-Bernal, E. (2017). ''Discovery of another new species of Charadrahyla Anura, Hylidae) from the cloud forest of northern Oaxaca, México.'' Zootaxa, 4329(1), 64-72. [link]
Duellman, W. E. (2001). The Hylid Frogs of Middle America. Society for the Study of Amphibians and Reptiles, Ithaca, New York.
Faivovich, J., Haddad, C. F. B., Garcia, P. C. A., Frost, D. R., Campbell, J. A., Wheeler, W. C. (2005). ''Systematic review of the frog family Hylidae, with special reference to Hylinae: phylogenetic analysis and taxonomic revision.'' Bulletin of the American Museum of Natural History, (294), 1-240. [link]
Faivovich, J., Pereyra, M.O., Luna, M.C., Hertz, A., Blotto, B.L., Vásquez-Almazán, C.R., McCranie, J.R., Sánchez, D.A., Baêta, D., Araujo-Vieira, K., Köhler, G., Kubicki, B., Campbell, J.A., Frost, D.R., Wheeler, W.C., Haddad, C.F.B. (2018). ''On the monophyly and relationships of several genera of Hylini (Anura: Hylidae: Hylinae), with comments on recent taxonomic changes in Hylids.'' South American Journal of Herpetology, 13(1), 1-32. [link]
Jiménez-Arcos, V.H., Calzada-Arciniega, R.A., Alfaro-Juantorena, L.A., Vázquez-Reyes, L.D., Blair, C., Parra-Olea, G. (2019). ''A new species of Charadrahyla (Anura: Hylidae) from the cloud forest of western Oaxaca, Mexico.'' Zootaxa, 4554(2), 372-385. [link]
Köhler, G., Trejo-Pérez, R. G., Reuber, V., Wehrenberg, G., Méndez-de la Cruz, F. (2016). ''A survey of tadpoles and adult anurans in the Sierra Madre del Sur of Oaxaca, Mexico (Amphibia: Anura).'' Mesoamerican Herpetology, 3, 640–660. [link]
Santos-Barrera, G., Canseco-Márquez, L. (2004). “Exerodonta juanitae”. The IUCN Red List of Threatened Species 2004: e.T55523A11325140. http://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T55523A11325140.en.
Snyder, D.H. (1972). ''Hyla juanitae, a new treefrog from southern Mexico, and its relationship to H. pinorum.'' Journal of Herpetology , 1972, 5-15. [link]
Originally submitted by: Jacob Slavik (first posted 2019-10-07)
Edited by: Ann T. Chang, Michelle S. Koo (2023-03-07)
Species Account Citation: AmphibiaWeb 2023 Charadrahyla juanitae: Rana-de Arbol de Juanita <https://amphibiaweb.org/species/833> University of California, Berkeley, CA, USA. Accessed Dec 2, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 2 Dec 2023.
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