Lepidopterans, including butterflies and moths, exhibit a great diversity of structural colors, that is, those that are not due to a certain pigment, but to the interaction of light with certain nanostructures present in some parts of the anatomy of animals; in this case, on the scales of their wings. This phenomenon produces bright and often iridescent hues, but the mechanisms involved are not yet fully understood.
Now, an international team of researchers from different institutions has studied the architecture of these scales in specimens from the Jurassic – between 200 and 145 million years ago – from Germany, the United Kingdom, China and Kazakhstan, as well as other extinct insects from the order Tarachoptera that were trapped in amber in what is now Burma in the mid-Cretaceous, about 100 million years ago.
In an essay published in the journal Science Advances , these scientists explain that to analyze their morphology they used different optical, electron and confocal microscopy systems. In this way they were able to observe the tiny grooves and ridges present in the scales, similar to those found in current butterflies. These marks, which measure between 140 and 2,000 nanometers – a nanometer is one billionth of a meter – are capable of scattering visible light and, as experts point out in a statement, would have given the wings a metallic appearance , between bronze and gold.
The evolution of color
The find is the first proof of the existence of structural colors in insects in the fossil record and sheds some light on the evolution of scales in Lepidopterans. Those of the aforementioned order Tarachoptera show, for example, a series of unique characteristics, such as their shape, reminiscent of a spatula, or their irregular distribution. “We did not expect to find the preserved wing scales, much less the microscopic structures that produce this type of color,” says paleobiologist Maria McNamara, from Cork University College, in Ireland, who has participated in this initiative. “It follows that color had a great importance in the evolutionary development of these limbs, even in the first ancestors of butterflies and moths,” he adds.
Bioengineer Wang Bo of the Nanjing Institute of Geology and Paleontology in China, who has coordinated the research, is convinced that this discovery has important implications. “The abundance of remains of this type in the Jurassic Lepidoptera and in the order Tarachoptera suggests that wing scales were already present in these animals much earlier than previously believed,” he says.
In the future, other studies could provide clues about the optical response of these nanometer-scale structures in other fossils. From them, it would be possible to build a model that allows us to elucidate the evolution of these colors in Lepidopterans.
Reference: Fossil scales illuminate the early evolution of lepidopterans and structural colors . Wang Bo et al. Science Advances . DOI: 10.1126 / sciadv.1700988
Image: Yang Dinghua
In an essay published in the journal Science Advances , these scientists explain that to analyze their morphology they used different optical, electron and confocal microscopy systems. In this way they were able to observe the tiny grooves and ridges present in the scales, similar to those found in current butterflies. These marks, which measure between 140 and 2,000 nanometers – a nanometer is one billionth of a meter – are capable of scattering visible light and, as experts point out in a statement, would have given the wings a metallic appearance , between bronze and gold.
The evolution of color
The find is the first proof of the existence of structural colors in insects in the fossil record and sheds some light on the evolution of scales in Lepidopterans. Those of the aforementioned order Tarachoptera show, for example, a series of unique characteristics, such as their shape, reminiscent of a spatula, or their irregular distribution. “We did not expect to find the preserved wing scales, much less the microscopic structures that produce this type of color,” says paleobiologist Maria McNamara, from Cork University College, in Ireland, who has participated in this initiative. “It follows that color had a great importance in the evolutionary development of these limbs, even in the first ancestors of butterflies and moths,” he adds.
Bioengineer Wang Bo of the Nanjing Institute of Geology and Paleontology in China, who has coordinated the research, is convinced that this discovery has important implications. “The abundance of remains of this type in the Jurassic Lepidoptera and in the order Tarachoptera suggests that wing scales were already present in these animals much earlier than previously believed,” he says.
In the future, other studies could provide clues about the optical response of these nanometer-scale structures in other fossils. From them, it would be possible to build a model that allows us to elucidate the evolution of these colors in Lepidopterans.
Reference: Fossil scales illuminate the early evolution of lepidopterans and structural colors . Wang Bo et al. Science Advances . DOI: 10.1126 / sciadv.1700988
Image: Yang Dinghua
