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University of Georgia (UGA) scientists studying North American bats have discovered six different species that glow in the dark when exposed to ultraviolet (UV) light.

Although several animals and plant species possess the ability to generate their own light, called bioluminescence, and some mammals, like pocket gophers, also emit a glow under ultraviolet light, called photoluminescence, the team says this is the first known evidence of bats in this part of the world emitting light in any spectrum.

The research team that discovered the glowing bats says they are not sure if this trait, which has been passed down to several generations from one original species, offers a current survival advantage or is simply a genetic relic that once offered enough survival benefits to propagate over time since it first evolved, but is no longer needed.

“It’s cool, but we don’t know why it happens,” said Steven Castleberry, corresponding author of the study and a UGA professor in wildlife ecology and management. “What is the evolutionary or adaptive function? Does it actually serve a function for the bats?”

In a statement detailing the team’s work, the researchers note that the illuminating discovery was made when examining 60 bat specimens stored at the Georgia Museum of Natural History. Specifically, the team found that when they exposed the specimens to UV light, several of the bat’s wings and hind limbs produced an eerie but clearly visible glow.

To determine the nature of the emitted light, the team measured the unexplained photoluminescence with a light-measuring sensor and found that the unexpected glow was a shade of green. Although they couldn’t immediately determine its function, the team said its location and color are likely to rule out an environmental cause. Instead, they suggest the ability to glow in the dark is likely a genetic trait.

“It’s ultimately some sort of mutation, and then that mutation somehow gets perpetuated, usually because it’s beneficial,” Castleberry explained. “Individuals that have that trait tend to survive and reproduce better, so it gets more common in the population.”

“There is evidence that glowing is a common trait,” the researcher added.

The study, co-authored by UGA alumnus Santiago Perea and Warnell graduate student Daniel DeRose-Broecker, details six bat species that glow in the dark. The photoluminescent species highlighted in the study included big brown bats, eastern red bats, Seminole bats, southeastern myotis, gray bats, and Brazilian free-tailed bats.

Briana Roberson, lead author of the study and a UGA alumna, noted that it’s possible that the function of glowing in animals may be “more diverse” than researchers previously thought.

“Bats have very unique social ecology and sensory systems, and the characteristics we found in these species differ from many other observations in nocturnal mammals,” Roberson explained.

When discussing possible reasons for the genetic mutation that causes bats that glow in the dark, the team noted that the color emitted under UV light was similar between the sexes. This similarity makes it less likely that the glowing ability is for reproduction or species recognition.

Further analysis seemed to rule out the glow being used as camouflage. Instead, the research team suspects the photoluminescence may represent an inherited trait once used for communication. Whatever the reason for these bats’ unusual ability to glow in the dark, the team says it probably comes from a single mutation that was likely passed along for a currently unknown survival advantage.

“The data suggests that all these species of bats got it from a common ancestor. Castleberry said. “They didn’t come about this independently.”

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