The glass frogs belong to the amphibian family Centrolenidae (order Anura), native to the Central American Rainforests.
Glass frogs are arboreal, living mainly in trees, feeding on small insects and only coming out for mating season.
The first described species of Centrolenidae was the "giant" Centrolene geckoideum, named by Marcos Jiménez de la Espada in 1872, based on a specimen 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 tree frogs in the genera Hylella or Hyla.
In 1973, John D. Lynch and William E. Duellman published a large revision of the glass frogs from Ecuador, showing the species richness of Centrolenidae was particularly concentrated in the Andes.
Later contributions by authors such as Juan Rivero, 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.
Character evolution seems to be complex, with multiple gains and/or losses of humeral spines, reduced hand webbing, and complete ventral transparency.
[4] However, they left a heterogeneous group of species in the genus Cochranella, defined just by lacking a humeral spine and a bulbous liver.
The monophyly of Centrolenidae is supported by morphological and behavioral characters, including: 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; and 5) eggs clutches deposited outside of water on vegetation or rocks above still or flowing water systems.
It was found in 2022 that these frogs have the ability to conceal red blood cells concentrated inside their livers, increasing transparency when they are vulnerable.
[12] An endangered species of glass frog found in Peru was compared to the N. mixomaculatus species and the following results were recorded: no humeral spine, no webbed fingers between II and III, finger I shorter than II, no vomerine teeth, no ulnar and tarsal tubercles or folds, no white pigment in the visceral or hepatic peritonea, and differing coloration and spots.
Mating begins by the call of a male tree frog, who is perched either on the underside or top of a leaf over a lake edge or a stream.
Males will occasionally call for and mate with other females on the same leaf, establishing a multitude of different developmentally-staged egg clutches to guard.
Hyalinobatrachium iaspidiense was observed having a flattened body posture to avoid predation, after disturbing the frog it propped up into a sitting position.
[13] The Centrolenidae are a diverse family, distributed from southern Mexico to Panama, and through the Andes from Venezuela and the island of Tobago to Bolivia, with some species in the Amazon and Orinoco River basins, the Guiana Shield region, southeastern Brazil, and northern Argentina.
[14] The eggs are usually deposited on the leaves of trees or shrubs hanging over the running water of mountain streams, creeks, and small rivers.