We've discovered recently that the world is much... brighter than we thought.
Biofluorescence is a phenomenon that has been increasing in popularity. It's a beautiful, soft glow that can be seen under ultraviolet light. The glow was also found in the segments of nests from several Asian wasp species.
The architectural styles of many species of the genus Polistes shine brightly under blacklight in varying degrees. This strongly suggests that the fluorescence may have a purpose, even though they don't show any signs of radiance.
Scientists could use this peculiarity to help them understand why the nests glow. It could also be used to identify a biofluorescent compound like the jellyfish-derived green fluorescent protein marker.
Bernd Schllhorn, a French chemist, was the leader of the research and hoped to discover more terrestrial biofluorescence.
ScienceAlert: "In the beginning, I was searching for any strongly fluorescent animals in the tropical rainforests." he explained to ScienceAlert. "Personallly, I was optimistic to find interesting organisms because this aspect remains under-explored."
Biofluorescence occurs when a living organism absorbs light and emits it at a different wavelength. To see this effect in humans, an external light source such as a UV lamp must be used. It has been observed in many species, most of them marine, but it is quite evident.
Frogs, scorpions and chameleons are some other organisms that biofluoresce. Turtles also biofluoresce. A surprising discovery was made recently with Australian marsupials like wombats or platypuses. You never know what other organisms could fluoresce in the dark.
This was the question that the French and Vietnamese teams set out to answer. They found the answers in four species nests, which were discovered during their daring forays into North Vietnam's tropical rainforests at night.
Fluorescing images of wasp nests. (de Marcillac et al., J. R. Soc. Interface, 2021
Schllhorn stated that visible fluorescence is best revealed at night. This adds a little adrenaline to field trips.
"One must be cautious and experienced as many reptiles and arthropods can be dangerous depending on their species and situation."
The team compared their findings to two Polistes species found in other parts of the globe: P. canadensis, French Guyana, and P. gallicus, southern France. Both of these were only slightly fluorescent compared to the Vietnamese wasps.
P. brunetus nest in white (left) or UV light (right). (de Marcillac et al., J. R. Soc. Interface, 2021
Researchers wrote that Vietnamese nests could be seen at night thanks to strong greenish-yellow fluorescence and portable UV LED torching.
"In the natural environment, strong fluorescence can easily be observed with the naked eye at distances between 5 and 20 meters [16 to65 feet], depending on species, nest size, and the power of the UV torch."
Particularly noteworthy were the cocoon caps which shone brightest on all nests. Microscopy showed fluorescence in silk fibers. This suggests that fluorophores, which are fluorescent chemical compounds, may be present in silk protein made by wasps.
Although the team didn't examine these species' visions, the spectral range of fluorescence emission falls within the general range for wasp vision. It could be that wasps can see the green glow. However, this may indicate that nests biofluoresce to help them recognize their home. This is possible even though two species showed very similar fluorescence profiles.
There is one more possibility. The fluorescence can be used to protect developing pupae against ultraviolet radiation. The incoming light is converted into benign optical light, which is then re-emitted. Biofluorescence could be used to perform this function, while still allowing light that is not harmful to the cocoon membrane.
They are currently investigating other species in the same genus to determine how biofluorescence differs by region. They are also working to identify the fluorescent substance in the wasp silk in order to discover a source of biofluorescence that can be used in biomedical research.
Schllhorn stated, "Most exciting to my is certain the fact that 'outthere' in the forest is a plethora unknown phenomena is still waiting for discovery."
The journal Journal of the Royal Society Interface published the research.
