Why do certain lizards have green blood?
Certain reptiles have bile pigments in their blood that are 40 times higher than a lethal concentration in humans. These lizards have somehow developed resistance to bile pigment toxicity. A new study has now explored the origins of these animals' unusual green blood.
In their current investigation, scientists from Louisiana State University and the American Museum of Natural History tried to find out why certain lizards have unusual green blood that contains a very high concentration of biliverdin. The doctors published the results of their study in the English-language journal "Science Advances".
Animals had resistance to biliary pigment toxicity
Aside from the high levels of biliverdin found in each animal, these lizards have somehow developed resistance to biliary pigment toxicity, says study author Zachary Rodriguez of Louisiana State University. For the current study, several expeditions to the depths of the New Guinea rainforest had to be carried out to observe the amazing diversity of reptiles and amphibians there. The scientists have particularly focused on the so-called green-flowered skinks that cannot be found anywhere else in the world, apart from the neighboring Solomon Islands.
DNA samples from 52 species of lizards were examined
On their expeditions, the researchers collected DNA samples from a total of 52 types of skinks, including six types with green blood. So far, two of these types of green blood have been completely unknown to science. With the help of the genetic information obtained, the researchers managed to create a kind of Skink family tree. This indicated that there are at least four different lines of green-flowered lizards. Each of these lines developed independently of their ancestors with red blood. “The complex history of these animals was very interesting and we were surprised by the variety of lizards with green blood,” explains Rodriguez.
Green blood was favored by natural selection
The fact that this trait appears to appear repeatedly suggests that green blood is not just an evolutionary peculiarity, but a useful trait favored by natural selection, the expert added. High levels of bilverdin were also found in the blood of various species of fish and insects, which are regarded as the cause of green bones, skin and blood in some types of frogs.
Can the blood protect against diseases?
The research results support the idea that green blood has an adaptive value, and laboratory studies indicate that the bile pigments can play a role as antioxidants or even protect against diseases, the doctors explain. The next goal will be to identify those genes that are responsible for green blood, says Rodriguez. If it can be determined why the lizards are protected from the harmful effects of excessive green pigments, this could lead to a better understanding of jaundice.
Does green blood also protect against malaria?
Understanding the underlying physiological changes that allowed these lizards not to develop jaundice symptoms could also affect non-traditional approaches to specific health problems, explains Rodriguez. Green blood lizards from New Guinea are fascinating to parasitologists because bilirubin is known to be toxic to human malaria parasites, says study author Prof. Susan Perkins from the American Museum of Natural History. The possible effect of the green blood pigment on malaria and other parasites that can infect these lizards is now being investigated. (as)