in 1969, some lizards in New Guinea attracted the attention of two biologists. When they dissected the lizards, they found that they were green to the bone: their bones and muscles were green, and green blood flowed through their veins.

(picture from: Christopher Austin)

how green is their blood? Just look at the picture below. Biologists classify the lizards as Prasinohaema, which means "green blood".

(a sample tube with green blood. Picture from: Christopher Austin)

in many cases, the color of animal blood is determined by the "elements" that carry oxygen in it. For example, our human blood is red, which comes from hemoglobin, which is used to transport oxygen. Creatures such as octopus, lobster and horseshoe crabs have blue blood because the protein they carry oxygen is a different version, in which the core metal ions change from iron to copper.

but there is another reason for the green blood of these lizards. Hemoglobin is responsible for carrying oxygen in their blood, which is no different from ours. Their blood is so green because another pigment occupies the plasma-biliverdin.

(chemical structure of biliverdin)

the researchers found that the green color in lizards' blood comes from biliverdin, which is so high in animals that the red color of hemoglobin is masked. One study measured plasma biliverdin levels in three green-blooded lizard species, with an average of 714 umol /L, 1020 umol /L and 819 umol /L, respectively. How high is this? For comparison, the highest recorded level of human blood biliverdin in the literature is only 50 μ mol/L (note: this is morbid, not normal).

this green looks amazing, but the more amazing thing is-why are green-blooded lizards safe and sound? Bilirubin and biliverdin are toxic metabolites. They are cytotoxic and can damage nerves. Animals generally do not allow these substances to accumulate in the body, but the liver is responsible for metabolizing them and excreting the metabolites through bile. Other animals are busy excreting the bile pigment metabolism, but these lizards allow biliverdin to accumulate in the blood to unimaginable concentrations, will their health not be affected?

at present, exactly how green-blooded lizards tolerate high concentrations of biliverdin need to be further studied. But the researchers do speculate about the reason for the evolution of green blood: it may help fight parasites. Studies have shown that biliverdin can inhibit the activity of parasites. In a recently published study, biologists analyzed the genes of several green-blooded lizards and found that the characteristics of green blood probably evolved independently several times, suggesting that green blood may indeed have a survival side.

there is green poisonous blood in his veins. This setting feels very interesting. I don't know if anyone wants to write a novel or something.

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reference:

https://www.theatlantic.com/science/archive/2018/05/why-do-these-lizards-have-green-blood/560543/

https://www.sciencedirect.com/science/article/pii/0300962994902011