Natures wonders: frogs go translucent (Introduction)

by David Turell , Friday, December 23, 2022, 00:26 (491 days ago) @ David Turell

By sequestering their red blood cells into their livers:

https://phys.org/news/2022-12-glassfrogs-red-blood-cells-liver.html

"Glassfrogs make themselves transparent while they rest by taking red blood cells from circulation and concealing them in their livers.

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"It's easy to miss a glassfrog in its natural environment. The northern glassfrog, Hyalinobatrachium fleischmanni, measures no more than a few centimeters, and they are most active at night, when their green skin helps them blend in with the surrounding leaves and foliage.

"But these amphibians become true masters of camouflage during the day when they're asleep.

"When glassfrogs are resting, their muscles and skin become transparent, and their bones, eyes and internal organs are all that's visible," said Carlos Taboada, a post-doctoral fellow at Duke and a co-first author of the paper. "These frogs sleep on the bottoms of large leaves, and when they're transparent, they can perfectly match the colors of the vegetation."

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"Glassfrogs are some of the only land-based vertebrates that can achieve transparency, which has made them a target for study. Taboada first began studying glass frogs as a post-doctoral fellow in the lab of Sönke Johnsen, a professor of biology at Duke who specializes in studying transparency. Working with Jesse Delia, who traveled around the world collecting different glassfrogs for the study, they observed that red blood cells seemed to be disappearing from the circulating blood whenever the frogs became transparent.

"They conducted additional imaging tests on the animals, proving via optical models that the animals were able to achieve transparency because they were pushing red blood cells out of their vessels. He suspected that the cells were being stored in one of the frog's inner organs which are packaged in a reflective membrane.

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"In their imaging set-up, the frogs slept upside down in a petri dish, similar to how they would sleep on a leaf, and the team shined a green laser at the animal. The red blood cells in the frog's body absorbed the green light and emitted ultrasonic waves, which were then picked up by an acoustic sensor to trace their whereabouts, with high spatial resolution and high sensitivity.

"The results were startlingly clear: When the frogs were asleep, they removed nearly 90 percent of their circulating red blood cells and stored them in their liver.

In further tests, the team also saw that red blood cells flowed out of the liver and circulated when the frogs were active, and then re-aggregated in the liver while the frogs were recovering.

"'The primary result is that whenever glassfrogs want to be transparent, which is typically when they're at rest and vulnerable to predation, they filter nearly all the red blood cells out of their blood and hide them in a mirror-coated liver—somehow avoiding creating a huge blood clot in the process," said Johnsen. "Whenever the frogs need to become active again, they bring the cells back into the blood stream, which gives them the metabolic capacity to move around."

"According to Delia and Taboada, this process raises questions about how the frogs can safely store almost all their red blood cells in their liver without clotting or damaging their peripheral tissues. One potential next step, they said, could be to study this mechanism and how it could one day apply to vascular issues in humans."

Comment: This is an internal trick, so how did frogs learn to turn it on? It is not an external instinct where one could learn from watching others. That is one problem. The next is clumps of red cells adhere together as clots/scabs. Something or some metabolite has to stop that. It is probable that falling asleep triggers the vanishing trick since one always follows the other. How does evolution create any of this? It can't. The trick is survival protection. If not present all at once, when the frogs appeared, they would not have survived until now. The disappearing clumped red cells had to be protected from clotting, so here again, the trick of disappearing and no-clotting had to be designed all at once. Irreducible complexity once again. /Can't/Doesn't appear without a designer. This is one of the best examples of God-must-design I've ever found