Description
Cruziohyla sylviae is a moderate to large sized species with males having a snout-vent length between 44.3 - 67.0 mm and females being between 73.5 - 88.2 mm. The body is elongated, robust for the genus. The head is wider than long and slightly broader than the body. The snout is sloping in profile, with nostrils having minimal protuberance and distanced slightly nearer to the upper lip than to the eye, whilst being distanced from each other by an interval about the same distance as from the upper lip. The canthus rostralis is not distinct and loreal region is slightly concave. The eyes are large, and pupil vertically elliptical. The palpebral membrane is transparent to partially-transparent, not reticulated. The tympanum is large, distinct, more than two-thirds diameter of the eye. A faint supratympanic fold is present. The vomerine teeth form two short oblique series located between the choanae. The tongue is oval-shaped, longer than wide, more than half the width of the mouth, and deeply notched anteriorly. The dorsal surfaces are smooth, and the ventral surface slightly granular; skin on the thighs and surrounding vent are coarsely granular. The upper arm is slender and the forearm robust, having a distinct dermal fold or ridge, almost ovoid in shape, and extending along the anterior edge of the forearm where it tapers from widest point of forearm to meet disk of the fourth finger. The fingers and toes possess large rounded disks. The subarticular tubercles on the fingers and toes are prominent and round. The fingers and toes are approximately ¾ webbed, with webbing extending to the base of the disc on the fourth finger and the penultimate phalange on the fourth toe. A distinct dermal ridge extends along the posterior ventrolateral edge of the tarsus, paralleling a less distinct inner tarsal fold extending along medial edge of tarsus. A triangular dermal flap is present on heel, which when hindlimb is withdrawn faces inward toward the vent (Gray 2018).

The tadpole of C. sylviae was described by Donnelly, et al. 1987, when the specimens concerned were first thought to belong to that of Agalychnis (Cruziohyla) calcarifer.

Cruziohyla sylviae can be distinguished from both other species in the genus, C. calcarifer and C. craspedopus, by a combination of the following characters: (1) it is a moderate to large sized species, with a snout-vent length in males of 44.3 mm to 67.0 mm and 73.5 mm to 88.2 mm in females; (2) the absence of dark brown patches on the vent seen in C. calcarifer; (3) a large distinct tympanum, diameter size more than 70% that of the eye; (4) fingers and toes extensively webbed (5) a sloping snout in profile; (6) in life, the presence of small irregular-shaped pale green lichenose speckles to whole of dorsal surface area; (7) bold black barring extends to lateral surfaces of the flanks, often interconnecting; (8) a triangular dermal flap on the heel, which faces inward when limb closes; (9) lack of a calcar terminating on heel projecting outward (Gray 2018).

Additionally, all Cruziohyla species have an overall dorsal coloration and patterning that is distinctly different: C. sylviae has a dorsal surface coloration consisting of two shades of green, with an areolated texture, giving a very finely granulated appearance, and also having small pale green lichenose speckles throughout; C. craspedopus has a uniform dark green dorsal surface background coloration with irregular-shaped large pale blue-grey lichenose blotches throughout; C. calcarifer has a consistent uniform green background coloration, often with a fine scattering of white or pale-blue spots, and possesses a small yellow colored spot directly posterior to the eye on the very rim. This marking, which is concealed when the frog is at rest, is lacking in both C. craspedopus and C. sylviae. Additionally, C. sylviae has extensive bold vertical black bars on its flanks and black barring on the upper surfaces of the thighs and the anterior surfaces of tibia (Gray 2018), whereas C. craspedopus has narrow black lines on the flanks (Funkhouser 1957), and C. calcarifer has black barring that is short and limited (Boulenger 1902).

In life, the dorsal surface coloration of C. sylviae combines two shades of green, with small pale lichenose speckling present throughout. The concealed surfaces of flanks, thighs, hands and feet, are orange-yellow. It has extensive bold vertical black bars on its flanks, black barring on the thighs’ upper surfaces and the anterior surface of tibia. The ventral surfaces of this species are pale orange-yellow. The eye contains two separate and contrasting colors: having a silvery-grey center with a yellow periphery. The lower eyelid is opaquely mottled, consistent with skin pattern of dorsal surface. In preservative, the dorsal ground color is dark greenish-grey, the lichenose markings are pale but as much emphasized as in life, and the orange colorations in life change to a cream color in preservative (Gray 2018).

There is little variation between adult specimens of C. sylviae apart from a sexually dimorphic size difference, however juveniles have a gray dorsal coloration which turns green with age (Kubicki 2004: sub C. calcarifer).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Costa Rica, Honduras, Nicaragua, Panama

View distribution map in BerkeleyMapper.

The type locality for C. sylviae is Guayacan, Costa Rica. It occurs at low-mid elevation localities (below 750 m) along the Cordillera Central of Central America, primarily along the Atlantic versant, from the Darien Province in southern Panama through Costa Rica and Nicaragua to southern Honduras (Gray 2018). It is mainly associated with primary rainforest habitat.

Life History, Abundance, Activity, and Special Behaviors
Advertisement calls of C. sylviae consist of single low-pitched note of 170 – 215 m/second duration repeated at regular intervals (Gray 2018).

Adult males use leg-waving behavior to communicate visually during territorial displays (Gray 2001).

The reproduction of C. sylviae differs little from that of Cruziohyla craspedopus: Egg clutches are deposited arboreally on leaves, roots and vines, over small pools and water-filled tree holes. Tadpoles drop into the water below upon hatching, where they swim using their wide flattened tails (Gray et al. 2021).

Trends and Threats
In recent years a greater number of Cruziohyla sylviae specimens have been recorded, not least through commendable efforts to help conserve them at the Costa Rican Amphibian Research Centre. However, habitat loss and fragmentation directly impacts the species’ future.

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing

Comments

Phylogenetic analysis of DNA sequences shows that C. sylviae is highly divergent from both other members of the genus: DNA sequences of the 16S rRNA gene confirms C. sylviae having minimum 6.2% genetic divergence from both C. calcarifer and C. craspedopus. Despite morphological similarities, phylogenetically C. sylviae is the sister species of C. craspeopus rather than C. calcarifer (Gray 2018).

The specific name “sylviae” is a patronym given in adoration of the author’s first grandchild, Sylvia Beatrice Gray. Sylvia originates from the Latin word for forest, Silva meaning ‘Spirit of the Forest’ (Gray 2018).

Until 2018 this species was confused with C. calcarifer, which is only known to occur from Ecuador to the southern most part of Costa Rica. By comparison, adults of C. calcarifer lack the lichen-like markings found on the dorsal surfaces of C. sylviae, have a tympanum to eye size ratio of approximately half, and have less barring to the flanks. Further distinctions between C. sylviae and C. calcarifer include C. sylviae having webbing that extends to the penultimate phalanx on the 4th toe (Duellman 1970: sub C. calcarifer) whereas C. calcarifer itself has more moderate webbing that extends to the antepenultimate phalanx on the 4th toe (Cochran and Goin 1970). All C. calcarifer specimens also posses unusual prominent dark ventral markings on the underside of the thigh region, which are totally absent in C. sylviae.

References

Boulenger, G.A. (1902). ''Descriptions of new batrachians and reptiles from north-western Ecuador.'' Annals and Magazine of Natural History, Series , 7(49), 51-57. [link]

Cochran, D. M. and Goin, C. J. (1970). ''Frogs of Colombia.'' United States National Museum Bulletin 288. Smithsonian Institution Press, Washington, D.C..

Donnelly, M. A., Guyer, C., Krempels, D. M., and Braker, H. E. (1987). ''The tadpole of Agalychnis calcarifer (Anura: Hylidae).'' Copeia, 1987(1), 247-250.

Duellman, W.E. (1970). The Hylid Frogs of Middle America. Monograph of the Museum of Natural History, University of Kansas.

Funkhouser, A. (1957). ''Review of the neotropical frogs of the genus Phyllomedusa.'' Occasional papers of the Natural History Museum of Stanford University, 5, 1-90.

Gray, A. R, Taupp K, Denès L, Elsner-Gearing F, and Bewick D (2021). "Description of the tadpole of Cruziohyla calcarifer (Boulenger, 1902) (Amphibia, Anura, Phyllomedusidae)." Herpetological Journal, 31(July, 2021), 7. [link]

Gray, A. R. (2018). ''Review of the genus Cruziohyla (Anura; Phyllomedusidae), with description of a new species.'' Zootaxa , 4450(4), 401-426. [link]

Gray, A. R. (2001). ''Investigations of visual and acoustic communication in the Agalychnis calcarifer.'' Master's Thesis, The University of Manchester, Manchester 148 pp.

Kubicki, B. (2004). Ranas de hoja de Costa Rica. Leaf-frogs of Costa Rica. Editorial Santo Domingo de Heredia, Editorial INBio, Costa Rica.

Species Account Citation: AmphibiaWeb 2021 Cruziohyla sylviae: Sylvia's Tree Frog; Rana arbórea de Sylvia <https://amphibiaweb.org/species/8884> University of California, Berkeley, CA, USA. Accessed Jan 29, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 29 Jan 2025.

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