DONG, Ying; FRIEDRICH, Markus; Wayne State University; Wayne State University: The effect of ecdysteroids on eye development in the grasshopper Schistocerca americana

The metamorphosis of holometabolous insects is controlled by the steroids hormone ecdysone and the lipid juvenile hormone. Ecdysone is secreted from the prothorathic gland and converted in peripheral tissues to the active form 20-hydroxyecdysone (20E) to regulate molting and metamorphosis. With regards to compound eye development, experiments in the tobacco horn moth Manduca sexta have demonstrated that both proliferation and maturation of the retina depend on the presence of 20E but are inhibited by high level of 20E. Also in Drosophila, retinal differentiation is disrupted by withdrawal of ecdysone. The regulatory functions of 20E during embryonic development in hemimetabolous insects are poorly known. We have therefore investigated the role of 20E during eye development in grasshopper Schistocerca americana after developing an in vitro culturing system for single grasshopper eye lobes. We found that 20E is not essential to sustain furrow progression and ommatidial maturation, which can occur in 20E free medium supplemented with the 20E antagonist Cucurbitacin B (CucB). Adding 20E, on the other hand, slightly accelerates retinal differentiation and ommatidial maturation. This effect can be suppressed by co-culturing with CucB. We also discovered a reduction in the size of 20E treated eye lobes. Taken together, our results demonstrate that the regulatory role of ecdysteroids changed dramatically during the evolution from hemimetabolous insects to holometabolous insects.