Glass frog

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Glass Frogs

Hyalinobatrachium ruedai

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Amphibia
Order:	Anura
Suborder:	Neobatrachia
Family:	Centrolenidae Taylor, 1951

Distribution of Centrolenidae (in black)

Genera

Centrolene
Cochranella
Hyalinobatrachium

• Glass frog is the common/popular name for the frogs of the amphibian family Centrolenidae (order Anura). While the general background coloration of most glassfrogs is primarily lime green; the ventral skin of some members of this family is transparent (species of the genus Hyalinobatrachium). The internal viscera, including the heart, liver, and digestive tract, can be seen due to the translucency of the ventral skin. This particular characteristic is the origin of their common name (Glass Frogs or Glassfrogs).

1 Historical Account of Taxonomy
2 Taxonomic classification
3 Diagnosis from other anurans
4 Distribution
5 Biology and Natural History
6 References
7 External links
8 Accounts for Glass frogs in other languages

[edit] Historical Account of Taxonomy

The first described species of Centrolenidae was the "giant" Centrolene geckoideum, named by the notable scientist Marcos Jiménez de la Espada in 1872, based on specimens collected in northeastern Ecuador. Several species were described in subsequent years by different herpetologists (including G. A. Boulenger, G. K. Noble, and E. H. Taylor) but usually placed together with the treefrogs in the genera Hylella and Hyla.

The family Centrolenidae was proposed by Edward H. Taylor in 1951. Between the 50s and 70s, most species of Glassfrogs were known from Central America, particularly from Costa Rica and Panama, where Edward H. Taylor and Jay M. Savage extensively worked, and just a few species where know to occur in South America. In 1973, John D. Lynch and William E. Duellman, published a large revision of the Glassfrogs from Ecuador, showing that the species richness of Centrolenidae was particularly concentrated in the Andes. Later contributions by authors like Juan Rivero, Jay Savage, William Duellman, John D. Lynch, Pedro Ruiz-Carranza and José Ayarzagüena increased the number of described taxa especially from Central America, Venezuela, Colombia, Ecuador, and Peru.

The taxonomical classification of the Glassfrogs was problematic during those years. Although four genera had been described for Centrolenidae (Centrolene, Centrolenella, Cochranella, Teratohyla), the taxonomical arrangements were always incomplete, and not valid for all species. In 1991, after a major revision of the species and taxonomic characters, the herpetologists Pedro Ruiz-Carranza and John D. Lynch published a new proposal for a taxonomic classification of the Centrolenidae based on cladistic principles and defining monophyletic groups ^[1]. That paper was the first of a series of contributions dealing with the Glassfrogs from Colombia that lead them to described almost 50 species of Glassfrogs. The genus Centrolene was proposed to include the species with a humeral spine in adult males; and the genus Hyalinobatrachium to the species with a bulbous liver^[1]. However, there was an heterogeneous group of species that they left in the genus Cochranella, defined just by lacking a humeral spine and a bulbous liver^[1]. Since the publication of the extensive revision of the Colombian Glassfrogs, several other publications have dealt with the Glassfrogs from Venezuela, Costa Rica, and Ecuador.

Recent molecular studies ^[2] have found that the three genera of Glassfrogs are non-monophyletic units, although taxon sampling was limited. The genus Centrolene is paraphyletic towards the genus Cochranella, and some species of Hyalinobatrachium were apparently more related to Cochranella. A reanalysis of morphological traits suggested a polyphyletic Centrolene and Cochranella, and supported the monophyly of the Hyalinobatrachium fleischmanni group ^[3] Other studies have addressed the same problem; e.g., in 2006 a scientific paper describing a new species of Centrolene from Ecuador ^[4] removed the species "Hyalinobatrachium pulveratum" and "Hyalinobatrachium antisthenesi" from Hyalinobatrachium and placed them inside the genus Cochranella as Cochranella pulverata and Cochranella antisthenesi. Although these changes keep Cochranella paraphyletic, they "clean" Hyalinobatrachium in order to define a monophyletic group. Further changes will need to be supported by extensive molecular and morphological analyses that are currently been developed by researchers from the University of Kansas, the U.S. Geological Survey/National Museum of Natural History, the Universidad San Francisco de Quito, the Pontificia Universidad Católica del Ecuador, and the Museo Ecuatoriano de Ciencias Naturales.

[edit] Taxonomic classification

The family Centrolenidae is a clade of anurans. Previously, the family Centrolenidae was considered closely related to the family Hylidae (tree frog); however, recent phylogenetic studies^[2] have placed the Centrolenidae (and its sister taxon the family Allophrynidae) closer to the family Leptodactylidae.

The monophyly of Centrolenidae (excluding Allophryne) is supported by morphological and behavioral characters including^[2] ^[4]: (1) presence of a dilated process on the medial side of the third metacarpal (an apparently unique synapomorphy); (2) ventral origin of the musculus flexor teres digiti III relative to the musculus transversi metacarpi I; (3) terminal phalanges T-shaped; (4) exotroph, lotic, burrower/fossorial tadpoles with a vermiform body and dorsal C-shaped eyes, that live buried within leaf packs in still or flowing water systems; (5) eggs clutches deposited outside of water on vegetation or rocks above still or flowing water systems. Several molecular synapomorphies also support the monophyly of the clade ^[2].

The taxonomic classification of Centrolenidae is still controversial, but currently three genera (with several species-group) of Glassfrogs are recognized:

Centrolene prosoblepon from Ecuador

Centrolene Jiménez de la Espada, 1872.
Centrolene geckoideum species-group
Centrolene prosoblepon species-group
Centrolene gorzulai species-group

Cochranella cf. albomaculata from Costa Rica

Cochranella Taylor, 1951.
Cochranella granulosa species-group
Cochranella ocellata species-group
Cochranella oyampiensis species-group
Cochranella spinosa species-group

Hyalinobatrachium ruedai from Ecuador

Hyalinobatrachium Ruiz-Carranza et Lynch, 1991.
Hyalinobatrachium fleischmanni species-group
Hyalinobatrachium parvulum species-group

Eleutherodactylus, note the form of the head and the snout, and the position of the eyes.

[edit] Diagnosis from other anurans

The Glassfrogs occur only in the Americas (see below Distribution), and in these regions they can be confused only with the greencolor members of the genus Eleutherodactylus or with Treefrogs of the family Hylidae.

However, hylids or Treefrogs have usually the eyes laterally directed whilst the Glassfrogs have them forward directed. Some species of green Treefrogs (especially juveniles) like Hyloscirtus palmeri and Hypsiboas pellucens have the ventral skin transparent but also have calcars on the heels, a character not present in any species of the family Centrolenidae.

Eleutherodactylus have the eyes laterally directed, the toes without membrane, and the snout is usually subovoid or subacuminate in dorsal view and the head is longer than wider.

[edit] Distribution

Centrolenidae is a diverse clade of anurans distributed in the Americas, from southern Mexico to Panama, and through the Andes from Venezuela to Bolivia, with some species in the Amazonas and Orinoco River basins, the Guiana Shield region, southeastern Brazil, and northern Argentina.

[edit] Biology and Natural History

Members of the family Centrolenidae are mostly arboreal frogs that live along rivers and streams (during the breeding season), and are particularly diverse in montane cloud forests of Central and South America, although some species occur also in Amazonian and Chocoan rainforest and semi-deciduous forests. The eggs are usually deposited on leaves of tree or shrubs hanging over the running water of mountain streams, creeks, and small rivers, or over stones close to waterfalls. The method of egg-laying on the leaf is species-specific. The males usually call from leaves close to their egg clutches. The eggs are much less vulnerable to predators than those laid within water, however there is a large risk of parasitism caused by a fly laying its larvae into the egg, so some species show parental care. After they hatch, the tadpoles fall into the waters below. The tadpoles are elongate, with powerful tails and low fins, suited for fast flowing water. During the non-breeding season some species live in the canopy.

[edit] References

^ ^a ^b ^c Ruíz-Carranza, P.M. and J. D. Lynch. 1991. Ranas Centrolenidae de Colombia I: propuesta de una nueva clasificación genérica. Lozania, 57, 1–30.
^ ^a ^b ^c ^d Frost D.R., Grant, T., Faivovich, J., Bain, R.H., Haas, A., Haddad, C.F.B., de Sa, R.O., Channing, A., Wilkinson, M., Donnellan, S.C., Raxworthy, C.J., Campbell, J.A., Blotto, B.L., Moler, P., Drewes, R.C., Nussbaum, R.A., Lynch, J.D., Green, D.M. & Wheeler, W.C. (2006) The Amphibian Tree of Life. Bulletin of the American Museum of Natural History, 297, 1–370. (PDF available by clicking here)
^ Guayasamin, J. M., M. R. Bustamante, D. Almeida-Reinoso, and W. C. Funk. 2006. Glass frogs (Centrolenidae) of Yanayacu Biological Station, Ecuador, with the description of a new species and comments on centrolenid systematics. Zoological Journal of the Linnean Society 147:489–513.
^ ^a ^b Cisneros-Heredia, D.F. & McDiarmid, R.W. (2006). A new species of the genus Centrolene (Amphibia: Anura: Centrolenidae) from Ecuador with comments on the taxonomy and biogeography of Glassfrogs. Zootaxa 1244: 1-32 - Description of Centrolene mariaelenae. (PDF of the abstract available by clicking here)