Lizard with toxic, lime-green blood discovered in New Guinea

Maricruz Casares
May 17, 2018

To their surprise, the results show that green blood evolved independently on at least four separate occasions. "The bones are green, the muscles are green, the tissues are green, the tongue and mucosal lining is green". Researchers said on Wednesday a DNA study resolved their family tree, finding that green-bloodedness evolved four different times among lizards called skinks on New Guinea.

Prasinohaema prehensicauda, a green-blooded skinkCHRISTOPHER AUSTINSeveral species of New Guinea skinks, a type of lizard, are just as colorful inside as they are outside-bright green blood runs through their veins, an oddity among animals. "There's so much green pigment in the blood that it overshadows the brilliant crimson coloration of red blood cells", says Chris Austin, a biologist at Louisiana State University who has studied these lizards for decades. These skinks' green blood comes from high levels of biliverdin, a green bile pigment that, when converted to bilirubin, causes jaundice. But these lizards thrive despite biliverdin levels many times greater than the lethal concentration in people.

Although all the green-blooded species have been assigned to a single genus, Prasinohaema, there were signs that they are not that closely related.

"They have other cool traits such as giving birth to live young and adhesive toe pads", Rodriguez added. This particular group of lizards might somehow be predisposed to evolving green blood, says Austin.

If that turns out to be true, the question is why some lizards would find it easier to be green.

We already know the broad mechanism. But he's offered the green-blooded lizards to captive birds, and the birds gobbled them right up.

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Another possible benefit the researchers considered was that all the extra green made for better camouflage in green leaves. "The problem is that there's green-blooded lizards that aren't green, and there's red-blooded lizards that are green", he explains.

The team's leading hypothesis is that the toxic green blood provides some protection against malaria, as higher than normal levels of biliverdin in human blood are known to kill malaria parasites.

Lately the scientists have been wondering if the lizards' green blood might protect them from parasites like malaria - although Austin admits that this is "pretty speculative".

However, the green-blooded lizards do still get malaria.

This basic research might someday lead to a better understanding of both this disease and jaundice, says Rodriguez.

"It's rare in the animal kingdom", says Rodriguez, "but because it does appear, this suggests there has to be some beneficial properties to green blood".

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