It’s time for another visit to the Department of Awesome Natural Wonders. These pretty amphibians with perfectly transparent underbellies are called Glass frogs. They live in the cloud forests of South america, are one of the relatively small number of species where the fathers exclusively care for the young, and scientists are still trying to figure out why they evolved to have transparent tummies.
Complete transparency has evolved multiple independent times. This suggests that a translucent underbelly provides some evolutionary advantage. Juan Manuel Guayasamin, an evolutionary biologist who studies glassfrogs extensively as a researcher at Universidad Tecnológica Indoamérica’s Center for Research on Biodiversity and Climate Change, explains:
"Most frogs are not transparent because this would expose organs to the deleterious effects of sunlight and heat." But in transparent glassfrogs, key organs like the liver and digestive tract are covered by a thin layer of light-reflecting organelles called iridiphores. These iridescent cellular subunits may provide a layer of protection from heat and sunlight, a feature that Guayasamin says could give glassfrogs the ability to optimize their internal homeostasis by simply moving about, "covering each organ at a time, as opposed to the entire body cavity."
Guayasamin says another hypothesis holds that transparency evolved to help glassfrogs avoid predators (an ability commonly referred to as “crypsis”). ”Most glassfrogs are green and reflect light almost as a leaf. For predators (and amphibiologists), it is quite difficult to find a glassfrog if it is not, for example, calling.”
You can even see their hearts beating inside their bodies. That’s pretty awesome.