Tag Archives: Scales

How butterflies have such a beautiful colour

Butterflies are some of the most exquisitely patterned and coloured creatures in the world. The colours all start with the scales on their wings. The scales contain crystals called gyroids that are made of chitin, the substance that is also in insect exoskeletons. These structures are complex and just a few nanometers large — so extremely tiny. Nanotechnology, creating tiny structures for industry, also creates such small-scale structures. They are important in areas such as medicine, electronics, and space travel. However, the nanostructures on butterfly wings are way more complex than anything that can be man-made. A group of researchers examined how the crystals develop on a butterfly’s wing for potential uses in industry.

The small Hairstreak. Image credits: Wilts et al., 2017.

The study that is published in Science Advances set out to discover how these crystals that give butterflies their magnificent colour form. It isn’t yet possible to study a butterfly’s wing while it’s developing, so the researchers examined the scales of a grown butterfly under extreme magnification. The subject? The small Hairstreak butterfly Thecla opisena from Mexico. The upper side is jet-black with blue patches while the lower side is green with a small red patch on the bottom edge of the wing. However, if you zoom into the bright green wing it’s actually not all green. The cover scales are bright green while the background is an orange-red colour. The cover scales themselves are not completely green but are made up of several domains that don’t overlap.

A close-up of one wing scale wing; it has a red background with green domains on top. Image credits: Wilts et al., 2017.

Each scale contains structured nanocrystals that interestingly, were spatially separated and loosely connected to the lower surface of the wing. On the wing, the crystals were arranged in lines, and at the beginning of the line the crystals were really small but as you progress further down the line, the crystals get larger. Perhaps, the scales form this way and are constantly growing on the wing. They seem to be developmental stages frozen in time and show the process of how these crystal form. The way that the scales develop is likely that the casing forms first and then the internal gyroid structure follows.

How the crystals develop over time. Image credits: Wilts et al., 2017.

We do need to keep in mind that this is just one butterfly out of more than 140,000 species. However, it is likely, according to the authors, that this way of development can be generalised to most wing scales and that all butterflies get their colour in a similar way. They could be very useful for nanotechnological applications, such as light-guiding technology because they can manipulate light in arbitrary directions. It is interesting to see how the natural world inspires technological advances.

Journal reference: Wilts, B.D. et al., 2017. Butterfly gyroid nanostructures as a time-frozen glimpse of intracellular membrane development, Science Advances.

Skin impression of one of the last dinosaurs found in Spain

Researchers from the Universitat Autònoma de Barcelona (UAB) working in collaboration with the Institut Català de Paleontologia Miquel Crusafont (ICP), have discovered an impression fossil preserving a Late Cretaceous dinosaur’s skin texture. This marks the time right before their extinction, making the fossil a unique discovery in Europe.

The dinosaur skin impression found at the site.
Image credits Víctor Fondevilla / UAB.

While performing a geological survey near the village of Vallcebre near Barcelona to study the origins of Late Cretaceous rock sediments (roughly 66 millions of years old), researchers found the impression of a dinosaur’s scales. They suspect the fossil formed when the animal had laid down in the mud, as the area corresponded to the muddy banks of a river during that time. The imprint was covered with sand which lithified into sandstone, preserving the relief of the animal’s original skin.

The Late Cretaceous ended with the extinction of the dinosaurs due to a violent meteorite impact. As such, there are very few places on Earth where intact sandstone deposits can be found from this period, making the find unique. Finding data to characterize these late dinosaurs is very important in understanding how they dealt with the extreme conditions and why they disappeared.

“This is the only registry of dinosaur skin from this period in all of Europe, and it corresponds to one of the most recent specimens, closer to the extinction event, in all of the world,” highlights UAB researcher Victor Fondevilla, main author of the research. “There are very few samples of fossilised skin registered, and the only sites with similar characteristics can be found in United States and Asia.”

“Other dinosaur skin fossils have been found in the Iberian Peninsula, in Portugal and Asturias, but they correspond to other more distant periods,” he adds.

The fossil shows scales in a pattern characteristic to some carnivorous dinosaurs and hadrosaurs: a central polygon-like bump surrounded by fire or six more bumps in the form of a rose. But the scales are too large compared to the typical size found in the dinosaurs roaming the area 66 million years ago.

“The fossil probably belongs to a large herbivore sauropod, maybe a titanosaurus, since we discovered footprints from the same species very close to the rock with the skin fossil,” Fondevilla says.

In fact, two skin impressions were found, one measuring approximately 20 centimeter wide, and the other slightly smaller, measuring only 5 centimeter wide, separated by a 1.5 meter distance and probably made by the same animal.

“The fact that they are impression fossils is evidence that the animal is from the sedimentary rock period, one of the last dinosaurs to live on the planet. When bones are discovered, dating is more complicated because they could have moved from the original sediment during all these millions of years,” Fondevilla adds.

The find will allow scientists to better recreate the dinosaurs before their extinction.

“The sites in Berguedà, Pallars Jussà, Alt Urgell and La Noguera, in Catalonia, have provided proof of five different groups of dinosaurs: titanosaurs, ankylosaurids, theropods, hadrosaurs and rhabdodontids,” explains Àngel Galobart, head of the Mesozoic research group at the ICP and director of the Museum of Conca Dellà in Isona.

“The sites in the Pyrenees are very relevant from a scientific point of view, since they allow us to study the cause of their extinction in a geographic point far away from the impact of the meteorite.”

The full paper “Skin impressions of the last European dinosaurs” has been published in the journal Geological Magazine.