It's difficult to identify a single evolutionary novelty in the animal kingdom that has fascinated and intrigued mankind more than the lantern of the firefly. Yet to this day, nothing has been known about the genetic foundation for the formation and evolution of this luminescent structure.
But now, new work from a former Indiana University Bloomington graduate student and his IU Ph.D. advisor offers for the first time a characterization of the developmental genetic basis of this spectacular morphological novelty -- the firefly's photic organ -- and the means by which this beetle successfully uses ancient and highly conserved regulatory genes to form its lantern.
"Our study demonstrates unprecedented roles for two Hox genes," said Armin Moczek, associate professor in the College of Arts and Sciences' Department of Biology and co-author on the paper with his former Ph.D. student Matthew Stansbury, now a postdoc at the University of Arizona. "These genes have been highly conserved over very long evolutionary times to lay out the basic body forms of so many animals, from humans to flies. Our study now shows that on top of that, these Hox genes have recently acquired control over important aspects of lantern development."
Hox genes are famous for specifying body regions and their boundaries, such as the head, thorax and abdomen of insects, or the cervical, thoracic and lumbar vertebrae of mammals. Hox genes are also famous for specifying which appendage will form on a given segment, such as a mouthpart in the head and a wing on the thorax, as well as specific modifications of these appendages: The beetle's forewing is a hardened shell rather than membranous due to the actions of a Hox gene, as is the reduction of the fly's hind wing to a tiny balancer organ.
What is nearly unprecedented, however, is that in the case of this beetle belonging to a family of about 2,000 species, the two Hox genes abdominal-A (abd-A) and Abdominal-B (Abd-B), appear to h
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