FaunaHub

Glass Frog (Hyalinobatrachium valerioi)

AmphibianFrogNeotropical

Glass frog (Hyalinobatrachium valerioi), a small green frog with translucent skin.

Reticulated glass frog (Hyalinobatrachium valerioi).

Image: Dan MacNeal, CC BY 4.0, via Wikimedia Commons.

Overview

Glass frogs (family Centrolenidae) are small, delicate tree frogs of Central and South American rainforests, named for their most extraordinary feature: the skin on their underside is translucent, so you can see the heart, liver, digestive organs — and sometimes even the beating heart — through the belly. Most are lime-green above, which blends with leaves, while the see-through underside helps hide them from below. The reticulated glass frog (Hyalinobatrachium valerioi) is shown here.

Beyond their startling transparency, glass frogs are notable for devoted fatherhood and for a recently discovered trick of becoming even more transparent while they sleep.

Note: there are many glass frog species; details here use the reticulated glass frog as a reference. Treat general statements as approximate and verify against authoritative sources.

Habitat & Range

Glass frogs live in humid tropical forests of Central and South America, almost always near streams. They are arboreal, spending their lives among the leaves of trees and shrubs overhanging running water, where they call, breed, and lay their eggs. They depend on healthy, undisturbed streamside forest.

Diet

Glass frogs are insectivores, feeding on small insects and other invertebrates — such as flies, ants, spiders, and tiny crickets — that they catch among the foliage. As small predators of insects, they are part of the web of life in streamside rainforest.

Behavior

Glass frogs typically lay their eggs on leaves hanging over a stream, and in many species the male guards the egg clutches — sometimes several at once — keeping them moist and defending them from predators and parasitic wasps until the tadpoles hatch and drop into the water below. Their transparency is more than a curiosity: research has shown that some glass frogs become markedly more see-through while asleep by hiding most of their red blood cells in the liver, reducing their visible outline — a striking natural camouflage trick.

Human Interaction & Conservation

Glass frogs are beloved by naturalists and photographers for their living-window bodies and are popular subjects in studies of camouflage and amphibian biology. Like many amphibians, they depend on clean water and intact forest, so deforestation, pollution, and disease are concerns; some species are threatened while others remain widespread. Consult AmphibiaWeb and the IUCN Red List for species-specific status.

More photos of the glass frog

A glass frog viewed to show its see-through underside and internal organs.

Glass frog (Hyalinobatrachium valerioi) — note the transparent belly.

Image: Nick Tobler (Cowturtle), CC BY 4.0, via Wikimedia Commons.

Frequently Asked Questions — Glass Frog

Can you really see a glass frog's organs?
Yes. The skin on a glass frog's underside is translucent, so through the belly you can see internal organs such as the heart, liver, and digestive tract — and in some species the beating heart is visible. The green back hides it on leaves, while the see-through underside helps conceal its shape from predators looking up from below.
Do glass frogs become more transparent when they sleep?
Some do. Research found that certain glass frogs hide most of their red blood cells in the liver while resting, which makes their bodies much more transparent and harder to spot as they sleep on leaves by day. When active, the blood returns to circulation. It's a remarkable, recently discovered camouflage mechanism.
Which parent looks after glass frog eggs?
Often the father. In many glass frogs the male guards the egg clutches laid on leaves over a stream — sometimes tending several clutches — keeping them moist and protecting them from predators and egg-eating wasps until the tadpoles hatch and fall into the water below. This paternal care is a notable part of their biology.
What do glass frogs eat?
Glass frogs are insectivores, eating small insects and other invertebrates such as flies, ants, spiders, and tiny crickets, caught among the streamside foliage where they live. As small insect predators they are part of the rainforest food web.

Sources and further reading

Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.