American researchers found that tarantulas evolved the same shade of blue hair at least eight different times. The discovery then raises more puzzling questions as to how this shift of appearance comes to the advantage of the arachnids.

The colors that living things exude are generated by selective absorption of specific wavelengths of light by pigments, nanostructure spread, or a combination of both.

Nanostructures produce color via different physical processes such as diffraction, interference and coherent scattering. The evolution of colors and the nanostructures change mostly due to complex relationships between sexual and natural selections for visual functions.

In a new study by scientists from University of Akron and University of California San Diego, the evolutionary tree of 53 tarantula species were mapped out by creating a supertree from past phylogenetic trees published.

The researchers collated digital images of tarantulas from Flickr and Google Images. They also purchased specimen from private sellers. In the end, the scientists chose eight species of tarantulas by chance based on photo descriptions and trade market availability.

To perform their investigations, the researchers used four main techniques, which include evolutionary tree reconstruction, electron microscopy, spectrophotometry and optical modelling. These processes enabled the experts to demonstrate antagonistic patterns of nanostructural variation, along with uncommon conservation of the blue hue in tarantulas.

The researchers then mapped out blueness in the evolutionary tree.

"If the genus has at least one species that's blue, we say that's a blue genus," said Bor-Kai Hsiung, one of the study's authors. After finding out that a certain specie belongs to a group of "blue colored" specimens, the researchers then measured the minimum number of times that blue color distribution changes transpired.

The verdict?

Tarantulas were found to have evolved on at least eight different occasions.

Given that tarantulas have poor vision, the colors do not likely have implications in mating patterns, Hence, the findings demonstrate color changes despite the absence of sexual selection.

Scientists think this discovery can help the industry of color-generating technology. "This potentially makes tarantulas a really important model for designing color-producing technology for TVs, phones, and other devices that are easier to look at," said study co-author Todd Blackledge from the University of Akron.

The study was published in the journal Science Advances on Friday, Nov. 27.