Unknown mechanism highlights how tadpoles stop UV

Amphibians might not be the animals you’d imagine would be built to survive climate change. They’re the most threatened group of animals on Earth, and are the main characters in the saying about what happens in a pot of slowly boiling water.

But new Australian research has found that one group of amphibians – tadpoles from the striped marsh frog – are surprisingly good at reducing damage caused by UV radiation, particularly if they’ve been exposed to colder temperatures.

“Amphibians are particularly vulnerable to UV exposure, experiencing increased mortality, defects, slowed development, DNA damage, physiological changes and reduced fitness,” said University of Queensland researcher Coen Hird.

“Traditionally it was thought high UV levels combined with cool temperatures had severe impacts on amphibian health.”

This is because declines in frog populations had occurred mostly in high-altitudes – areas with higher levels of UV radiation and cooler temperatures. But this wasn’t what happened in this experiment.

The researchers took the striped marsh frog tadpoles and reared them at either 15 degrees or 25 degrees for around 20 days. They then measured the DNA damage from an hour and a half of high UV radiation – while putting them in water ranging in temperature from 10 to 30 degrees.

“The tadpoles exposed to UV in cooler temperatures were able to completely compensate for UV-induced damage, through thermal acclimation,” Hird said.

“This suggests that as climate change and ozone depletion continue to modify temperatures and UV exposure, species with greater capacity for acclimatisation may be more resilient.”

The researchers assumed that his was caused by the tadpoles turned themselves dark in colder temperatures, and this protected them from the UV.

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“But to our surprise, we discovered this was not the case at all,” said Hird.

“Instead, the tadpoles likely alter or increase their DNA repair enzymes to counteract the impact of cold temperatures on UV-induced DNA damage.

“This opens the door to a new understanding of how amphibians adapt to changing environments and is testament to their resilience in the face of climate challenges.”

The team hope that this may provide more information for researchers looking at amphibian conservation, and maybe even a bit of optimism to how they will survive climate changes as the planet heats up.

“There may also be broader implications for understanding how various species adapt to environmental changes, offering hope for the conservation of vulnerable ecosystems worldwide,” said Hird.

The research is published in the Journal of Thermal Biology and JEZ-A Ecological and Integrative Physiology.

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