Scientists have discovered that four different kinds of lizards independently evolved toxic green blood. They're still not sure of the benefits of lizards having the green blood, but finding out could give them an idea about human illnesses such as jaundice.

The substance found in the lizard's blood is toxic for humans.

Green Everything

Green-blooded skinks found in New Guinea have green blood due to high levels of biliverdin, which is a green bile pigment. Biliverdin is toxic and causes jaundice. The blood of skinks contains 40 times the lethal concentration found in humans. Despite this, the lizards are healthy.

Biliverdin causes the lizards to have lime-green blood, muscles, bones, and tongues. It is a toxic waste product that is made during the body's breakdown of red blood cells. Skinks were found to have the highest concentration of biliverdin in any animal, and they have developed a resistance to the toxicity of biliverdin. 

Researchers in the study believe that understanding the physiological changes that have let the skinks be jaundice-free could lead to a better understanding of health problems caused by biliverdin. For the study, 51 species of skinks were analyzed. This included six species with green blood. Two of the green-blooded species were newly discovered.

Origin Of Green Blood

Scientists previously believed that green-blooded skinks may be part of a closely related group, but this wasn't the case. All of the green-blooded species of skinks don't look anything alike and live different lifestyles. Some of the skinks lay eggs, and others give birth to live young.

While analyzing, they found that there were four separate lines of green-blooded skinks. Each line shared an ancestor that originally had red blood. Researchers determined that green blood evolved four times. Scientists found that it came about independently in each of the species of skinks. They think that this means that the green blood may be a valuable adaptation.

Elevated levels of bile pigments have been found in animals such as insects, fish, and frogs in the past. Bile pigment has been shown to act as an antioxidant scavenging free radicals and preventing diseases during in-vitro fertilization. Having elevated levels of bile pigments was a positive advantage for those animals. Now, scientists are trying to see how the green blood may help the skinks. 

Researchers are also trying to determine if the green-blood is related to malaria prevention. Another liver product bilirubin is similar to biliverdin but is toxic to human malaria parasites. They're trying to determine the effects of biliverdin on malaria and other parasites that are affecting the skinks.

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