Researchers may have figured out toxic, lime green lizard blood

Henrietta Strickland
May 17, 2018

"Our current hypothesis is that this novel and toxic physiology might have evolved to reduce or preclude the infection of blood parasites such as malaria", Austin said.

High levels of biliverdin cause jaundice in most animals, but these lizards thrive despite biliverdin levels many times greater than the lethal concentration in people. They're still not sure of the benefits of the lizards having the green blood, finding out could give them an idea about human illnesses such as jaundice.

So Austin, Perkins, and their colleague Zachary Rodriguez chose to create a kind of lizard family tree by studying the DNA of 51 Australasian skink species, including six species that have green blood.

It is odd to believe that with such high levels of bile pigment, these lizards live a healthy life.

Lately the scientists have been wondering if the lizards' green blood might protect them from parasites like malaria - although Austin admits that this is "pretty speculative".

In a study published Wednesday, scientists explain that the lizards' blood - as well as their muscles, bones, and tongues - are bright green because they contain high levels of biliverdin. For the research, a team from LSU examined 51 types of skink lizards-including six species with green blood, two of which are new to science-by analyzing the DNA of various specimens.

The green blood is among the most unusual characteristics that one can find in the animal kingdom but it is a distinguishing characteristic for a group of lizards that are found in New Guinea. In this tube, red blood cells are on the right and green blood plasma is on the left. This happens as their entire bodies have high concentrations of biliverdin.

Researchers in the study believe that understanding the physiological changes that have let the skinks be jaundice-free could lead to a better understanding of health problems caused by biliverdin. But these lizard species don't look alike and have different lifestyles, with some laying eggs and others giving birth to live young. This green bile pigment is produced in the process of breaking down the oxygen-transporting molecule hemoglobin into the bile pigment bilirubin.

The fact that green blood emerged independently on numerous occasions suggests it may be evolutionarily beneficial, according to the researchers. The researchers say the next step is to identify the specific genes responsible for green blood.

Elevated levels of bile pigments have been found in animals such as insects, fish, and frogs in the past. They think that this means that the green blood may be a valuable adaptation. While the function of the green bile in the lizards remains uncertain, several studies have shown that that bile pigment can have antioxidant properties and also helps to prevent disease during in vitro fertilization.

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