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Insect Morphological Diversification Through the Modification of Wing Serial Homologs

Science  26 Apr 2013:
Vol. 340, Issue 6131, pp. 495-498
DOI: 10.1126/science.1234219

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A Wing by Another Name?

Wings and their derivatives on the second and third thoracic segments represent the only known dorsal appendages in modern insects; however, the existence of wing homologs in non-winged segments has been suggested from fossil insects. Ohde et al. (p. 495, published online 14 March) identify part of the body wall on the first thoracic segment and pupal dorsolateral outgrowths as modified pairs of wings in the mealworm beetle. These organs could be transformed into wings and thus share the central wing developmental mechanism.

Abstract

Fossil insects living some 300 million years ago show winglike pads on all thoracic and abdominal segments, which suggests their serial homology. It remains unclear whether winglike structures in nonwinged segments have been lost or modified through evolution. Here, we identified a ventral lateral part of the body wall on the first thoracic segment, the hypomeron, and pupal dorsolateral denticular outgrowths as wing serial homologs in the mealworm beetle Tenebrio molitor. Both domains transform into winglike structures under Hox RNA interference conditions. Gene expression and functional analyses revealed central roles for the key wing selector genes, vestigial and scalloped, in the hypomeron and the denticular outgrowth formation. We propose that modification, rather than loss, of dorsal appendages has provided an additional diversifying mechanism of insect body plan.

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