People can see the beating heart of the see-through Glass Frog. But, its blood is less visible. Scientists have recently discovered why. The Glass Frog hides its blood in its liver when it sleeps.
The Glass Frog (Hyalinobatrachium yaku) and the Fleischmann’s Glass Frog (Hyalinobatrachium fleischmanni) live in the tropical, dense Amazonian lowlands of Ecuador.
The size of a marshmallow, the amphibians are called Glass Frogs because their skin is translucent and transparent (see-through). Jesse Delia at the American Museum of Natural History in New York said to the New Scientist LIFE magazine in 2022, “If it wasn’t for that green skin on their back, you would probably be able to read a newspaper through them.”
Being transparent helps the Glass Frog avoid predators. But, if people can see their beating heart, then surely their predators could see their heart and blood. Researchers were keen to study the Glass Frog’s transparency more closely.
Jesse Delia and his colleagues began studying the Glass Frog after noticing that they seemed to be more transparent when they were sleeping. The researchers conducted several light transparency tests while the frogs were sleeping and when they were active. They found that Glass Frogs became up to 61% more transparent when sleeping, by storing – or hiding – up to 90% of their blood in their liver.
The researchers traced the movement of the frogs’ blood using photoacoustic imaging. About 90% of their red blood cells where in their liver during sleep. Their liver enlarged by 40%. When the frogs woke up and their blood circulation increased, they became less translucent and their livers went back to their usual size.
With other animals, storing blood in the liver would cause blood clots that could kill the animal, but Glass Frogs don’t get blood clots. Now the researchers want to find out more from the Glass Frogs so that they can help humans with blood clots.
Journal reference: Science, DOI: 10.1126/science.abl6620
Photographs are from the New Scientist LIFE magazine, 22 December 2022
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