Can a tropical lizard (Xenosaurus platyceps) survive freezing temperatures?

Area of Science:

• Herpetology
• Ecology
• Physiology

Background:

• Thermoregulation is vital for lizards, employing strategies like stenothermy or eurythermy, and active or passive methods.
• Organisms in cold environments use freeze avoidance (supercooling) or freeze tolerance, often with glucose as a cryoprotectant.
• Xenosauridae lizards are typically thermoconformers, with some species maintaining low body temperatures.

Purpose of the Study:

• To investigate the thermal ecology of Xenosaurus platyceps in a tropical, low-elevation population.
• To examine thermoregulatory behavior, cold tolerance, and blood glucose maintenance throughout the year.
• To analyze seasonal variations in thermoregulation, supercooling points, and glucose concentrations.

Main Methods:

• Field observations and experimental freezing of Xenosaurus platyceps.
• Monitoring of body temperature in relation to environmental and substrate temperatures.
• Analysis of seasonal thermoregulatory patterns, supercooling points, and blood glucose levels.

Main Results:

• Xenosaurus platyceps demonstrated experimental freezing survival, a first for the Xenosauridae family.
• Body temperature significantly correlated with environmental and substrate temperatures, showing stenothermic behavior (20.8–30.8 °C).
• Lizards exhibited active thermoregulation in spring/winter, thermoconformity in autumn, and heat avoidance in summer, with supercooling points as low as -7.01 °C and increased blood glucose post-freezing.

Conclusions:

• Xenosaurus platyceps displays significant seasonal thermal adaptability and resistance to sub-zero temperatures.
• The species utilizes a combination of behavioral and physiological strategies for thermoregulation and freeze tolerance.
• This study highlights unique cold adaptation mechanisms in a tropical lizard species.