The humble platypus continues to surprise us. One of only five mammals that lay eggs, the Australian duck-billed creature can now add biofluorescent fur to its curious genetic makeup. When exposed to ultraviolet (UV) light, the platypus' brown fur turns a bright greenish-blue. The discovery is reported in the journal Mammalia.
Members of the same research group discovered last year that flying squirrels are bubble-gum pink under UV light. Researchers were studying lichens at night when they discovered flying squirrels glowing under their UV torches. Specimens at the Field Museum of Natural History in Chicago confirmed this too. Moved by curiosity, the researchers shone a UV light on platypus specimens too and found they started glowing.
“It was a mix of serendipity and curiosity that led us to shine a UV light on the platypuses at the Field Museum,” lead author Professor Paula Spaeth Anich, from Northland College, said in a statement. “But we were also interested in seeing how deep in the mammalian tree the trait of biofluorescent fur went. It’s thought that monotremes branched off the marsupial-placental lineage more than 150 million years ago. So, it was intriguing to see that animals that were such distant relatives also had biofluorescent fur.”
The team looked at three museum specimens, a male and female from the Field Museum as well as a second male specimen from the University of Nebraska State Museum. They found the fur of the platypus absorbs UV light and re-emits it in wavelengths of light we can see, making it fluoresce. The fluorescence was strongest on the animal stomach. The pattern is not sexually dimorphic, meaning both males and females glow in the same places and intensity.
The third mammal that we know to possess biofluorescence is the opossum. All three species are active at dusk, dawn, and during the night, so this peculiar ability may have something to do with being visible to other members of its species when it's dark.
The researchers believe that the ability of the platypus to bioflouresce could be an adaptation against predators who are sensitive to UV light. "However, field-based research will be essential to document platypus biofluorescence and its ecological function in wild animals," they write.