Green blood may sound like something out of a horror movie, but there are a group of lizards that live on the large island near Australia that actually have lime-green blood.
They are called green-blooded skinks. Skinks are smooth lizards with very small legs that live in the tropics. It’s not just their blood that is green. They also have bright, lime-green muscles, bones and tongues.
The green blood is caused by high levels of biliverdin, a color that makes bile green. Bile is a fluid that helps digest food. You have bile in an organ called the gallbladder. But skinks have levels of biliverdin that are about 40 times higher than what would kill a human.
Out of 51 lizards that scientists from Louisiana State University examined in New Guinea, six had green blood, but they also found a total of 27 lizards with green blood to help with their study. The scientists are wondering what’s the advantage to having green blood and why doesn’t it kill the animals, since it is so dangerous to humans?
Over many, many years, the skinks evolved to build up a resistance to the bile. It could be that the high levels of biliverdin helps them avoid diseases, like malaria, that are common to jungle areas. Some other fish, frogs and insects have more biliverdin, too.
The strange thing is that the scientists found that all of these green-blooded lizards, way back in their past, had red-blooded ancestors. This is one more strange evolutionary finding that demonstrates how little we know about the animal world and how much even lizards are capable of teaching us.
— Brett French, firstname.lastname@example.org