Too much fun in the sun? UV rays are shrinking frogs
- Isabella Yantsis
- Mar 22, 2023
- 3 min read
By: Isabella Yantsis
For most people, sitting out by the pool and lounging in the sun sounds like the perfect pastime. The sun-kissed glow our skin gets from being outside is an aesthetic perk that many of us strive for. While humans may appreciate soaking up the sun’s rays during a trip to the beach, this isn’t quite the case for amphibians. In fact, having too much fun in the sun may have deadly consequences.
With the increasing threat of climate change, the protective cloud of gasses around the Earth’s atmosphere has degraded. As a result of this damaged barrier, greater amounts of ultraviolet-B (UVB) exposure from the sun have passed through to Earth. UVB exposure events have been observed more frequently, and have been associated with declines in amphibian populations. Niclas Lundsgaard and his team of researchers from The University of Queensland were interested in exploring UVB exposure on amphibians, and chose the Australian green tree frog as their model organism. Their main goal was to understand how exposing UVB to tadpoles would affect them after metamorphosis, which is the developmental transition from a tadpole to adult frog. The team theorized that higher amounts of UVB applied to tadpoles would negatively affect their development into adulthood.
Lundsgaard and his team were interested in UVB irradiance, which is the amount of radiation energy received per square centimeter of a surface. To put it into perspective, you could imagine raindrops on an umbrella as a measure of radiation energy on a surface. A light mist with minimal raindrops could be considered low irradiance, while an intense thunderstorm with many drops would represent high irradiance. To understand the effects of early UVB exposure, Lundsgaard’s group of tadpoles were subjected to three intensities of irradiance: low, medium, and high. The tadpoles were reared to adulthood in the lab, and underwent regular check-ups throughout the duration of the experiment to track their weight and growth. To track their physical fitness, adult frogs underwent an amphibian boot camp where their hunting performance was judged.
It turns out that the shrink ray devices shown in science fiction movies may not be too far off from real life. That is, the tadpoles exposed to high UVB irradiance grew up to be smaller in size as adults! Their smaller condition made adult life much trickier, as they failed to hunt as efficiently as their larger, stronger friends. These findings implied that high UVB irradiance exposure, even for a short duration during the tadpole stage, had a huge effect on the performance of the adult frog. Their decreased ability to hunt suggested a lower chance of long-term survival, and also tied into the idea that UVB exposure events are related to the observed declines in amphibian populations.
As another indicator of health, Lundsgaard’s team measured a small portion of each frog’s DNA. These regions, called telomeres, gave scientists an idea of how UVB exposure affected the adult frog’s lifespan. Telomeres shorten over the course of an animal’s lifetime, meaning longer telomeres are associated with a longer lifespan. Similar to their body size results, telomeres of the UVB-exposed frogs were found to be very short in length. While this is just another reason for frogs to stay away from tanning beds, it also suggests that UVB exposure caused premature ageing in the frogs and had a negative impact on their health.
The important takeaway is that high UVB irradiance not only affects amphibians, but could also harm a variety of other species. With the prevalence of climate change, the frequency and intensity of UVB exposure may continue to increase. Moving forward, it is important that humans make a conscious effort to advocate for environmental protection and reverse the effects of climate change. As well, stocking up on sunscreen probably wouldn’t be a bad idea either.
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