Why Do These Lizards Have Toxic Lime-green Blood?

Why Do These Lizards Have Toxic Lime-green Blood?

Why Do These Lizards Have Toxic Lime-green Blood?

A pair of LSU scientists has found the biological cause of odd, lime-green blood found in several species of New Guinea lizards could unlock cures for malaria and jaundice in humans, according to an LSU news release.

"In addition to having the highest concentration of biliverdin recorded for any animal, these lizards have somehow evolved a resistance to bile pigment toxicity", lead author Zachary Rodriguez, a doctoral candidate in Austin's lab at Louisiana State University, explained in a statement released Wednesday.

But these lizards are beginning to give up some of their secrets, including their evolutionary history. The team studied the DNA of 51 species of New Guinea skinks, including six with green blood.

They found that green blood in these lizards likely evolved four different times, and that all of the green-blooded lizards were probably descended from a red-blooded ancestor. The name of this green-blood lizard's group or a type of lizard is known as Prasinohaema. Its green blood and body contains 40 times the concentration of biliverdin that is enough to kill a human.

Green blood likely emerged independently in various lizards, which suggests that green blood may have an adaptive value. Several fish, frog and insect species also are green-blooded.

"I find it just absolutely remarkable that you've got this group of vertebrates, these lizards, that have a level of biliverdin that would kill a human being, and yet they're out catching insects and living lizard lives", says Susan Perkins, a researcher at the American Museum of Natural History in NY.

"We were excited by the complex history of these animals and surprised by the breadth of green-blooded lineages across lizards", Rodriguez said. "Understanding the underlying physiological changes that have allowed these lizards to remain jaundice-free may translate to non-traditional approaches to specific health problems". It turned out that numerous species with green blood aren't closely related to one another, and have more in common phylogenetically with red-blooded skinks.

"Oh, these animals are gorgeous, truly some of the most attractive and enigmatic lizards in the world, living on one of the most mega-diverse islands on the planet", Austin said. The other species that sport green blood give birth to live young.

If the green blood is protective against malaria, it's not perfectly so, because they've found a malarial parasite living inside a green-blooded lizard, says Perkins. It's possible the green blood protects the animals from malaria, as in vitro studies have shown that human blood with high levels of bilirubin, a close relative, can stave off infection. Still, they're continuing to explore what kind of relationship there might be between malaria and green blood.

Previous studies suggest bile pigments can take on an antioxidant role, finding and neutralizing free radicals.

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