“Animal blood comes in a rainbow of hues
because of the varying chemistry of the molecules it uses to carry
oxygen. Humans use hemoglobin, whose iron content imparts a crimson
color to our red blood cells. Octopuses, lobsters, and horseshoe crabs
use hemocyanin, which has copper instead of iron, and is blue instead of
red—that’s why these creatures bleed blue. Other related molecules are
responsible for the violet blood of some marine worms, and the green
blood of leeches. But the green-blooded lizards use good old hemoglobin.
Their red blood cells are, well, red. Their green has a stranger
origin: Biliverdin.

They should be dead. Biliverdin can damage DNA, kill cells, and destroy
neurons. And yet, the lizards have the highest levels of biliverdin ever
seen in an animal. Their blood contains up to 20 times more of it than
the highest concentration ever recorded in a human—an amount that proved
to be fatal. And yet, not only are the lizards still alive, they’re not
even jaundiced. How do they tolerate the chemical? Why did they evolve
such high levels of biliverdin in the first place? And why, as Austin’s
colleague Zachary Rodriguez has just discovered, did they do so on
several occasions?”

Source: TheAtlantic

These Lizards Are Full of Green Blood That Should Kill Them