How an insect got its wings remains a mystery that has been puzzling biologists for more than 100 years now. Interesting and opposing theories of insect wing evolution have developed in recent years, although none were completely acceptable.
Finally, a group of researchers from the Marine Biological Laboratory, Woods Hole, has stabilized the controversy through the use of clues from scientific papers done a long time ago, including state-of-the-art genomic methods.
The research, which Heather Bruce, MBL Research Associate, and Nipam Patel, MBL Director, conducted, is published this week in Nature Ecology & Evolution.
Based on findings, the team confirmed that insect wings "evolved from an outgrowth or 'lobe' on an ancestral crustacean's legs."
How Insect Wings are Formed
After this marine animal had evolved to land-dwelling around 300 million years ago, the leg segments nearest to its body became integrated into the body wall during the development of the embryo, probably to better back its weight on land.
Bruce explained, the leg lobes then moved upwards onto the back of the insect, which then formed the wings afterward. The research associate added, one of the reasons it took 100 years to discover this is that it was not accepted until around 2010 that insects are most closely linked to crustaceans "within the arthropod phylum" as the genetic similarities revealed.
Before that, added Bruce, based on morphology, everyone had categorized insects in the myriapod group, together with centipedes and millipedes.
And, if one is to look in myriapods where wings of insects are coming from, the expert continued explaining, he won't find anything.
Therefore, insect wings appeared to be perceived as 'novel' structures springing up in insects and did not have a corresponding construction in the ancestors as scientists were searching for the wrong location for the insect ancestor.
Novel Innovation
According to Patel, people are getting very excited by the notion that something like insect wings may have been "a novel innovation of evolution."
Nonetheless, one of the stories developing from genomic comparisons is that there is nothing new and all of these findings had their origin.
In an article posted on SciTechDaily, it was indicated that Bruce "picked up the scent of her now-reported discovery" while she compared the genetic instructions for a crustacean's legs, the "tiny beach-hopper Parhylale," and the segmented insect legs, which included Drosophila fruit fly, and the Tribolium beetle.
Through the use of a gene-editing called CRISPR-Cas9, Bruce systematically had five shared leg-patterning genes disabled in Parhyale, as well as in insects. She also found an additional seventh of the leg segments, next to its body wall.
To know where that particular segment went, the expert started to dig in the literature, and she discovered this really old notion that had been proposed as early as 1893, that insects had integrated their closest-to-body leg region into the body wall.
Still, she explained, she did not have that "wing part" of the story. Therefore, she continued reading and reading and encountered this 1980s theory that not just insects combine their closest-to-body leg region into the body wall, but the small lobes on the leg moved up onto their back and formed the wings.
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