Australia's green-and-golden bell frog was hiding a surprising secret in plain sight.
Scientists have discovered that the skin on the inner thighs of this animal changes color from blue to green depending on the direction of light.
For a species that is critically endangered and already considered iconic, this discovery adds another compelling reason to pay attention to how many more surprises biodiversity may have in store for us.
What's happening?
At Newcastle University, scientists have discovered an unusually pronounced iridescent effect in an amphibian – the endangered green-and-golden bell frog, or Ranoidea aurea.
Their work shows that this species exhibits angle-dependent coloration in areas of the skin that have not previously been observed.
The team presented their findings in the journal Austral Ecology, along with photographs of the usually hidden skin of the frog's inner thigh. These images show that from some angles, this area appears blue, while from others, it appears green.
Lead author of the study, conservation biologist Dr. John Gould from Newcastle University, said in a statement published by Phys.org: "Iridescent glow occurs when the color changes depending on the viewing angle.".
Researchers believe these bright spots may act as a flash of color. If the hidden skin is suddenly exposed when the frog jumps or moves, the splash of color could startle or distract a predator long enough for the animal to escape.
Why is this important?
The obtained results may prompt a re-evaluation of both the methods of color formation in frogs and the methods of self-defense of these animals in natural conditions.
Many blue hues in animals are caused not by pigment, but by tiny structures that affect light. In this case, the iridescent glow indicates the presence of carefully organized reflective plates—a mechanism more akin to butterfly wings than to random light scattering.
Such knowledge can help biologists better understand how species evolved defenses against predators and how specialized traits may be linked to habitat health. This knowledge contributes to more effective conservation of wetlands and other ecosystems, which humans also depend on for flood protection, clean water, and resilience to climate change.
Endangered animals are not static entries on a list of endangered species. They are living parts of ecosystems that can still reveal new biological characteristics.
What is being done?
This discovery opens a new starting point for scientists to study structural coloration in amphibians.
Discoveries like these can strengthen the case for protecting species like the green and golden bell frogs, demonstrating that we still have much to learn about them. This, in turn, can help support habitat restoration programs, monitoring, and rebuilding frog populations in threatened areas.
Healthy frog populations are often a sign of a healthier ecosystem, and healthier ecosystems tend to promote healthier human communities.
«"It's a remarkable optical effect, but it's very rare in amphibians," Gould said. "Two people in different locations can look at the same patch of tissue at the same time and see different colors.".
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