Meeting Abstract
The origin of metamorphosis is one of the biggest mysteries in insect evolution. In particular, the evolution of the larval morphology remains poorly understood. To identify the mechanism underlying the development of the specialized larval appendage morphology, the role of Hedgehog (Hh) signaling was examined in two insects: a hemimetabolous insect, the large milkweed bug, Oncopeltus fasciatus, and a holometabolous insect, the red flour beetle, Tribolium castaneum. RNA interference-mediated knockdown of the components of the Hh signaling pathway showed that Hh is required for both larval limb maturation and outgrowths in Tribolium castaneum, but only for limb maturation in Oncopeltus fasciatus. Our findings suggest that Hh signaling plays both shared and derived roles in limb development of hemimetabolous and holometabolous insects. In addition, the relationship between endocrine regulators of metamorphosis and Hh signaling will be discussed. We will present a model for the evolution of metamorphosis in which Hh signaling was co-opted for larval appendage outgrowth, conferring sensitivity to endocrine regulators responsible for metamorphosis.
