Lizards and a cure for malaria

Prasinohaema prehensicauda is a green-blooded lizard with high concentrations of biliverdin, a toxic green bile pigment.

G reen blood? And that too in lizards? Yes. Scientists at the Museum of Natural Science (MNS), Lousiana State University, Baton Rouge, have found that green blood, one of the most unusual characteristics in the animal kingdom, is the hallmark of a group of lizards in New Guinea. More importantly, they may just help in finding a cure for malaria.

Prasinohaema, as they are called, are green-blooded skinks, a type of lizard. The muscles, bones and tongues of these lizards appear bright lime-green due to high levels of biliverdin, or a green bile pigment, which is toxic and causes jaundice. With such high levels of green bile—40 times higher than lethal concentrations in humans—these lizards should be dead. But, surprisingly, they remain healthy.

“In addition to having the highest concentration of biliverdin recorded for any animal, these lizards have somehow evolved a resistance to bile pigment toxicity. Understanding the underlying physiological changes that have allowed these lizards to remain jaundice-free may translate to non-traditional approaches to specific health problems,” said the lead author Zachary Rodriguez, working in Chris Austin’s laboratory at the MNS.

“A similar liver product, bilirubin, is known to be toxic to human malaria parasites. Ongoing work with Austin’s lab examines the potential effect of the green blood pigment on malaria and other parasites that infect these lizards,” said co-author Susan Perkins, a parasitologist of the Sackler Institute for Comparative Genomics at the American Museum of Natural History.

Rodriguez, Austin and colleagues investigated 51 species of skinks, which included six species with green blood, two of which are species new to science. They discovered that there are four separate lineages of green-blooded lizards, and each may have a red-blooded ancestor. Their results have been published in a recent issue of the journal “Science Advances”. According to the scientists, green blood likely emerged independently in various lizards, which suggests that it may have an adaptive value. Slightly elevated levels of bile pigments in other animals, including insects, fish and frogs, have had potentially positive roles.

Previous studies have shown that bile pigment can act as an antioxidant, scavenging free radicals in these animals as well as preventing disease during in vitro fertilisation. However, the function of green bile pigment in these lizards is still uncertain.