Lizards with green ‘inside’

Washington, May 17: Lizards whose anatomy is green inside had puzzled biologists earlier. Not anymore.

An educated guess by scientists, Allan Greer and Gary Raizes, who found three of such species in New Guinea in 1969, had suggested that the green colour inside them was the result of a green pigment called biliverdin. It is created when red blood cells that only live for four months or so, die and bodies recycle the iron within them.

Biliverdin is usually converted into a yellow pigment called bilirubin.

Both of these are toxic, and human liver quickly filters them out of the blood. Under normal circumstances, the presence of biliverdin should have killed the lizard. It can damage DNA, kill cells, and destroy neurons.

The lizards have the highest levels of biliverdin ever seen in an animal. Their blood had 20 times more of biliverdin than the highest concentration ever recorded in a human.

The questions that surfaced as a result of this finding is how do they tolerate the chemical? Why did they evolve such high levels of biliverdin in the first place?

It’s an unusual physiological trait that’s only found in New Guinean lizards. The green-blooded species evolved from red-blooded ancestors on four separate occasions. They all independently showed up to life’s party with green in their veins.

The team can’t rule out the possibility that the lizards evolved green blood once and then reverted to red on several occasions. Whatever be the case, the team of scientists agree that they need to be reclassified.