Glass Frog of the Costa Rican Rainforest

At first glance, the glass frog of the Costa Rican rainforest may seem like an easy target for predators due to its nearly transparent skin. However, this unique species has developed a clever adaptation to evade danger while it sleeps. A recent study published in the journal Science has revealed that when a glass frog falls asleep, almost all of its red blood cells retreat into its liver, allowing it to become nearly invisible to predators. This remarkable adaptation not only provides insight into the diverse and intricate ways in which animals have evolved to survive in their environments, but it may also hold clues for preventing deadly blood clots in humans.

A Transparent Evolution

While translucence is a rare trait in animals that live on land due to the presence of substances in their bodies that light cannot penetrate, glass frogs seem to have evolved see-through versions of some of these essential anatomical features. In addition, they have developed a way to hide lingering colors when they are at their most vulnerable. When awake, the circulatory system of the glass frog is red due to the presence of haemoglobin, a colored protein in red blood cells that delivers oxygen throughout the body. However, when the frog falls asleep, this color disappears.

To understand this intriguing phenomenon, biologists Jesse Delia and Carlos Taboada, authors of the new study, wanted to compare images of sleeping and anesthetized frogs to see where the red blood cells were going. Utilizing ultrasonic waves to identify the contents of the frog’s organs, the researchers found that about 89% of the red blood cells had retreated to the liver when the frog was asleep. The liver, which filters blood, is a logical destination for red blood cells when they are not in circulation. However, the researchers were puzzled by how the frogs were able to cram all of these cells together without forming deadly blood clots.

Preventing Blood Clots in Humans

In most vertebrates, the coagulation of blood cells when they come into contact with each other leads to the formation of a clot, which can either seal a wound or, if located in a blood vessel, block the circulatory system and cause death. In the United States alone, 100,000 people die from blood clots each year. The findings of the new study suggest that glass frogs have the ability to control when their blood clots, forming a scab when wounded but avoiding clotting when their red blood cells are packed into the liver while sleeping. If future research can reveal the mechanism behind this ability, it could lead to treatments that reduce deaths from blood clots in humans.

Breathing While Asleep

The researchers also noted that if 89% of the cells responsible for carrying oxygen are stored in the liver while the frog sleeps, how is it able to breathe? They speculate that the frog may have developed a way to redirect oxygen from other parts of the body to the liver, allowing it to continue functioning while in this state of near invisibility. Further research is needed to fully understand this mysterious adaptation and the potential implications for human health.

The glass frog of the Costa Rican rainforest is a fascinating and unique species that has evolved a clever way to evade predators while it sleeps. By retreating almost all of its red blood cells into its liver, it becomes nearly invisible, avoiding detection by would-be predators. This adaptation raises interesting questions about how the frog is able to continue breathing while in this state and holds potential clues for preventing deadly blood clots in humans. Further research is needed to fully understand this intriguing species and the potential implications of its adaptations.