Many animals have developed camouflage tactics for self-defense, but some butterflies and moths have gone even further: They have developed transparent wings that make them almost invisible to predators.
A team led by scientists from the Marine Biology Laboratory (MBL) is investigating the development of one such species, the glass-winged butterfly, Greta oto, to see the secrets of this natural stealth technology. Their work is published in Journal of Experimental Biology.
Although transparent structures in animals are well established, they occur much more frequently in aquatic organisms. “This is an interesting biological issue because there just aren’t that many transparent organisms on land,” said lead author Aaron Pomerantz, Ph.D. PhD in Integrative Biology, University of California, Berkeley. “So we asked the question, what is the real basis for developing how they create their transparent wings?”
Butterfly wings are known for their colorful patterns created by small, overlapping, chitinous scales that reflect or absorb different wavelengths of light to produce colors. Pomerantz says that although scale coloring has been intensively studied, a study of the origins of transparency in land butterflies has not been done before. “Transparency is the opposite of color,” he says.
Pomerantz and his co-authors, including his doctorate. MBL Advisor and Director Nipam Patel, were inspired by the work of students in the MBL embryology course in which Patel teaches. “I decided to bring some of the transparent species of butterflies and moths I had in my collection that I never looked at in detail in the course and present it as a challenge for students to see how transparent these wings are,” says Patel. “A group of students took advantage of this by imaging the wings with different microscopes. And they realized that in almost any way to think about making the wing transparent, some butterfly or moth figured out how to do it. Here’s what made us look in more detail in the development of transparency. “
Based on this work, the researchers used confocal and scanning electron microscopy to build a timeline for the development of how transparency occurs in Greta, from the puppy phase to adulthood. They found that the wings of the glass-winged butterfly develop differently from opaque species, with a lower density of precursor cells in areas that will later develop as transparent. At a very early stage, scale growth and morphologies differ, with thin, bristle-like scales developing in transparent regions and flat, round morphologies in opaque regions.
“What Greta oto does is make fewer scales and make them in these very different, bristle-like shapes,” explains Patel. “But the removal of the scales is only part of the problem of creating transparency. Aaron also made a series of observations of wing nanostructures that prevent glare in bright sunlight. When light enters these small arrays of nanostructures, it’s not” not. reflects – it goes straight. So it gives much better transparency, “he said.
“As humans, we think we’re so brilliant because we figured out how to put anti-glare coating on glass, but butterflies basically invented it tens of millions of years ago,” says Patel.
The unusual scales of the wings and nanostructures are only part of the story. A second layer of waxy hydrocarbon nano-columns lies on the surface of the wing, providing additional anti-reflective properties. The researchers examined the reflectivity of the wings before and after removing the wax layer with hexane.
“We measured the amount of light reflected from the wing,” says Pomerantz. “These experiments have shown that the top layer is very important in reducing glare.” Biochemical analysis showed that the wax layer was composed mainly of long chains of n-alkanes, similar to those found in other insect species. “They are considered primarily to help prevent dehydration or desiccation of the insect. But in this case, they also appear to be used for these anti-glare properties.”
Future research guidelines may include deepening the way in which these transparent structures have developed. Pomerantz points out that “if we can learn more about how nature creates new types of nanostructures, it can be very informative about human applications.” The work makes the secrets of natural transparency much less opaque.
Glass frogs, ghostly shrimp and butterflies with clear wings use transparency to avoid predators
Aaron F. Pomerantz et al, Developmental, cellular and biochemical basis of transparency in butterflies with clear wings, Journal of Experimental Biology (2021). DOI: 10.1242 / jeb.237917
Provided by the Marine Biology Laboratory
Quote: How Butterflies Make Transparent Wings: Scientists See the Invisible (2021, June 10), extracted on June 11, 2021 from https://phys.org/news/2021-06-butterflies-transparent-wings-scientists-invisible .html
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