Vitellogenesis and Post-Vitellogenic Maturation of the Insect Ovarian Follicle

Female insects typically produce prodigious numbers of eggs to assure the propagation of their genes, and invest considerable resources towards this end. Ulti- mately, the egg of an insect must contain a haploid set of chromosomes, sufficient nutrients to supply the growing embryo with resources to last until the larva or nymph ecloses and begins feeding, and a set of determinants to direct the organization and progres- sion of embryogenesis, including the differentiation of a new cluster of germ cells. As with all organs, the morphology of the ovary reflects the physical and genetic requirements of its physiological role, which in this case is the functional assembly of the various components of the oocyte. Visual inspection shows that the polytrophic ovary of holometabolus insects, which represent a major focus of this chapter, is comprised of a series of ovarioles that contain linear arrays of progres- sively developing follicles starting with dividing germ stem cells at one end and ending with mature oocytes ready for fertilization at the other ( Figure 1). Essentially, the ovariole can be considered an assem- bly line leading to the production of the egg. How this assembly line operates within different species to produce similar end products, i.e., the mature oocytes, depends on the insect, its life style, and its evolutionary history.This is a chapter from Swevers, L., A. S. Raikhel, T. W. Sappington, P. Shirk, and K. Iatrou. 2005. Vitellogenesis and post-vitellogenic maturation of the insect ovarian follicle. In: L. I. Gilbert, S. Gill, and K. Iatrou (eds.), . Vol. 1, Reproduction and Development. Elsevier, NY, pp. 87-155. doi: 10.1016/B0-44-451924-6/00093-4. Posted with permission.</p

Comparison of the activity of ecdysone agonists in Bombyx mori and Spodoptera littoralis by in vitro reporter assays and in vivo toxicity assays

Trabajo presentado en el 17th International Ecdysone Workshop, celebrado en Ulm (Alemania) del 20 al 24 de junio de 2008.Ecdysone agonists such as dibenzoylhydrazines have been successfully used in biological control programs of lepidopteran and coleopteran pests. However, little information exists with respect of the specificity of the action of such compounds towards different species of Lepidoptera or Coleoptera. In this study, we compare the activity of ecdysone agonists belonging to three different chemical classes (dibenzoylhydrazines, acylaminoketones and tetrahydroquinolines) between the lepidopteran pest Spodoptera littoralis and a beneficial lepidopteran species, the silkworm Bombyx mori. The activity of ecdysteroid agonists is measured both in vitro, using an ecdysone-responsive reporter assay based on transfected or transformed Spodoptera- or Bombyx-derived cell lines (Sl2 and Bm5 cells, respectively), and in vivo, by toxicity tests on Spodoptera and Bombyx larvae. The study aims at the elucidation of the species-specific factors that determine the activity of ecdysone agonists against Lepidoptera.Peer Reviewe