Unprecedented lead tolerance in an urban lizard.

Area of Science:

• Environmental Toxicology
• Ecotoxicology
• Vertebrate Physiology

Background:

• Lead (Pb) is a pervasive and highly toxic heavy metal pollutant.
• Environmental lead exposure poses significant health risks to wildlife and humans.
• Previous research indicates lead negatively impacts vertebrate performance.

Purpose of the Study:

• To quantify blood lead concentrations in Cuban brown anole lizards (Anolis sagrei) in New Orleans.
• To determine the lead toxicity threshold for whole-organism performance in this species.
• To investigate the molecular mechanisms underlying potential lead tolerance in Anolis sagrei.

Main Methods:

• Field sampling to measure blood lead levels in free-living Anolis sagrei.
• Controlled laboratory experiment to establish lead toxicity thresholds through lead dosing.
• Transcriptomic analysis of brain and liver tissues from lizards exposed to varying lead levels.

Main Results:

• Anolis sagrei in New Orleans exhibit the highest reported mean blood lead concentrations (955 μg/dL) among free-living vertebrates.
• Despite extreme exposure, no significant decrease in balance, sprint speed, or endurance was observed in field-exposed lizards.
• The blood lead threshold for performance impairment was found to be exceptionally high (10,600 μg/dL), exceeding mean field concentrations by an order of magnitude.

Conclusions:

• Anolis sagrei demonstrates an unprecedented level of tolerance to lead exposure.
• Differentially expressed genes suggest cellular mechanisms related to metal ion homeostasis and oxygen transport contribute to this tolerance.
• The Cuban brown anole serves as a promising model organism for understanding vertebrate lead tolerance mechanisms.