Overview
The Yaku Glassfrog (Hyalinobatrachium yaku) is an extraordinary, jewel-like treefrog discovered in 2017 in the Amazonian lowlands of eastern Ecuador. Named ‘yaku’ from the indigenous Kichwa word for water, this miniature amphibian captivated evolutionary biologists with its virtually transparent ventral skin that completely exposes its red beating heart, digestive tract, and hepatic organs in living color without dissection.
Biology and Physical Characteristics
Measuring barely two centimeters in length, Hyalinobatrachium yaku features an apple-green dorsal surface peppered with tiny yellow dots that mimic fungal spores or moss growth on wet rainforest leaves. Its most astonishing anatomical marvel is its completely transparent ventral parietal peritoneum and pericardium: through its glassy underside, observers can clearly witness the rhythmic contractions of its bright red cardiac chambers and the intricate network of blood vessels. Males possess distinct high-pitched tonal vocalizations with unique frequency modulations used to claim leaves above swift river currents.
Behavior and Ecology
Yaku Glassfrogs are strictly nocturnal and obligate stream dwellers. Males establish calling territories on the undersides of broad leaves hanging directly over rushing rocky streams. After attracting a female and completing amplexus, the female deposits a clutch of gelatinous eggs on the leaf. The male remains vigilantly behind, actively guarding the egg clutch against predatory wasps, spiders, and fungal infestation until the embryos mature and drop straight down into the torrential current below to complete development as aquatic tadpoles.
Conservation and Human Impact
Formally categorized as Data Deficient by the IUCN, field biologists recognize that the Yaku Glassfrog faces acute ecological vulnerabilities. Its reliance on pristine, unpolluted, highly oxygenated forest streams makes it hyper-sensitive to sedimentation, agrochemical runoff, and road development associated with petroleum extraction in the Ecuadorian Amazon. Preserving clean watershed buffers across the Yasuní and Pastaza basins is vital to its long-term survival.
Interesting Factoid
The underside of the Yaku Glassfrog is completely clear like glass: you can look directly through its chest skin and watch its bright crimson heart beating in real time.
Last updated: October 2026