A green-blooded lizard

Unlike most animals, the prehensile tailed skink (Prasinohaema prehensicauda) from the highlands of Papua New Guinea has green blood.

The muscles, bones and tongues of these lizards appear a bright lime green due to high levels of biliverdin, a green bile pigment, which is toxic and causes jaundice. Surprisingly, these lizards remain healthy with levels of green bile that are 40 times higher than the lethal concentration in humans.

No-one knows exactly how the skinks (and several related species of lizard) tolerate the poisonous pigment, but recent research shows that green-bloodedness may have evolved independently at least four times.

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