Two American researchers have taken a significant step to unveil one of the greatest mysteries of evolution: how insects acquired the ability to fly, inform The New York Times.
In their study, Yoshinori Tomoyasu and David Linz, evolutionary biologists at the University of Miami, explain how they managed to genetically design beetle larvae with wings on their abdomens.
Insects learned to fly between 300 and 360 million years ago, long before birds, bats or pterosaurs. The vast majority of them today have wings or have evolved from flying ancestors, says Linz.
The problem is that there is no fossil evidence that corresponds to the period in which the flying abilities of insects evolved. Hence a wide variety of hypotheses about the origins of its wings. In other words, that evolution occurred so long ago that “it is very difficult to say what happened”, explains Tomoyasu.
For a long time there have been two rival hypotheses about it. The ‘tergal hypothesis’ suggests that the wings originated in the tergum, the upper part of the body shell of the insect, probably as planetary membranes. The ‘pleural hypothesis’ argues that the wings originated in the old segments of the legs, which fused with the body before ending up in the back.
The emergence of the evolutionary biology of development, together with genetic advances, have given weight to a third possibility, the hypothesis of double origin. Raised in 1974, it assumes that the wings of the insects represent the fusion of two separate tissues: the dorsal wall of the body provided the membrane, while its articulation arose from the segments of the legs.
Although this type of evolutionary fusion sounds strange, there are precedents. The ancestors of the inspectos probably had relatively symmetrical body segments, each with a pair of legs. These segments were modified in very different ways over the millennia. So that in some the legs were lost in the abdomen, in others they moved towards the head, becoming antennas.
Tomoyasu and Linz worked with Tribolium , or flour beetles, given their genome completely sequenced. They do not fly well and it’s easy to keep them in the laboratory.
In their initial study, the researchers deactivated certain genes from the beetles to manipulate wing segments of the body. To his surprise, this affected anatomical parts that had seemed unrelated to flight, which supported the idea that wings are composite tissues.
Then the scientists paid attention to the pupae, which have sets of miniature defensive clamps along their abdomens. These are located near the top of the insect, which makes them a likely model of the early structures of the wings.
Tomoyasu and Linz introduced a green fluorescent protein in the beetles, which marked the expression of certain genes linked to the wings, to facilitate the detection of tissues affected by genetic manipulation. The result was two green tissues: one in the area of the dorsal clamps and the other in the pleural tissue.
From there, they proceeded to produce pupae in which both tissues fused to form pairs of tiny wings.
In search of more evidence
However, the debate about the evolution of insect wings is still far from over.
“For the time being we are basing [the study] on a species. Although we see that it is two tissues that make the wings, this could be exclusive for this lineage, “explained Tomoyasu.
Therefore, it is necessary to study more insects and this team is now dedicated to cockroaches and some crustaceans, to see if the process is repeated in the same way.
At the same time, Tomoyasu keeps a bit of hope that a fossil finding will one day help solve the mystery.
“We are very confident about our analyzes, but it is a prediction. It would be great to see the shape of an ancestral insect, “said the co-author of the study, published in Proceedings of the National Academy of Sciences.