Lizards carrying deadly lead levels: They should be dead, but they are surviving

Lead contamination is a serious environmental and public health issue, affecting both humans and wildlife. Urban areas often have lead in old paint, soil, and from industrial activities, creating a toxic environment over decades. Surprisingly, some animals have adapted to survive in these conditions, revealing remarkable biological resilience. One extraordinary example is the brown anole, a small, invasive lizard that thrives in New Orleans. A study published in the Journal Environmental Research shows that these lizards tolerate lead levels that would be fatal for most vertebrates, offering unique insights into adaptation, environmental monitoring, and the hidden effects of heavy metal pollution.The brown anole (Anolis sagrei), also called the Bahamas anole, is native to the Bahamas and Cuba. Over time, it has become highly invasive across the southern United States, including New Orleans.These tiny reptiles absorb lead in several ways:Direct contact with contaminated soil or old lead-based paint.Eating insects that have ingested lead.Slowly absorbing small amounts from the environment over time.Even with blood lead levels hundreds of times higher than what would kill humans, brown anoles continue to survive and reproduce. Their ability to tolerate toxic heavy metals makes them a valuable subject for research into environmental health.Lead contamination in cities primarily comes from old paint, contaminated soil, and industrial activity. In New Orleans, older urban areas like Tulane have higher lead levels due to legacy paint, while suburbs like Lake Shore have lower contamination, partly due to remediated soil. Tropical storms and erosion can also spread lead from old buildings into the environment.Brown anoles pick up lead in three main ways:Direct contact with contaminated soil or paint.Eating insects that have ingested lead.Absorbing small amounts from their environment over time.The study found brown anoles with lead concentrations far exceeding any previously recorded levels in vertebrates. One lizard had a staggering 3,192 micrograms per decilitre of lead in its blood, while the average was 955 per decilitre. For context, blood lead levels above 10 decilitre in humans are considered dangerous. These lizards tolerate levels hundreds of times higher than what would be fatal to humans. Lizards from older urban areas had higher lead levels than those from suburbs, reflecting environmental contamination levels.In mammals and birds, lead exposure causes severe health problems, including organ damage, neurological issues, and death. Previous studies in New Orleans also linked lead tolerance to behavioural traits in mockingbirds, but the effect on reptiles is far more striking.Tests on brown anoles showed that even lizards with the highest lead levels performed normally in balance, sprinting, and endurance tests. Unlike other vertebrates, these reptiles seem remarkably resilient to heavy metal toxicity.Brown anoles, however, remain active and healthy despite extremely high lead levels. Laboratory tests showed no significant differences in balance, sprinting, or endurance between lizards with high and low lead exposure. This resilience sets reptiles apart from other vertebrates.Genetic analysis revealed that lizards with high lead levels expressed certain genes differently than those with lower levels. Some of these genes are linked to heavy metal tolerance and oxygen transport. Lead can interfere with cells’ ability to carry oxygen, so enhanced oxygen-carrying capacity may help these lizards survive toxic exposure.This discovery suggests that reptiles may possess unique biological mechanisms to tolerate heavy metals, offering potential insights for wildlife conservation and even human health research.Also read| James Webb Space Telescope reveals ghostly dust rings: This “dead” star surprises astronomers