Fine structure and morphogenesis of the micropylar apparatus in the medfly Ceratitis capitata (Wiedemann) (Diptera : Tephritidae) |
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| Institution: | 1. SNSB – Bavarian State Collection of Zoology, Münchhausenstraße 21, 81247 München, Germany;2. Ludwig-Maximilians-Universtity, Biocenter, Großhaderner Straße 2, 82152 Planegg-Martinsried, Germany;3. Department of Life Sciences, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy;1. Department of Cardiology, First Affiliated Hospital, Cardiovascular Research Center, School of Basic Medical Sciences, Xi''an Jiaotong University, Xi''an, China;2. Max Planck Institute for Heart and Lung Research, Department of Pharmacology, Bad Nauheim, Germany;3. Center for Mitochondrial Biology and Medicine, School of Life Science and Technology, Xi''an Jiaotong University, Xi''an, China;4. Department of Vascular Cell Biology, Max Planck Institute of Molecular Biomedicine, Muenster, Germany;5. Center for Molecular Medicine, Goethe University Frankfurt, Frankfurt, Germany;6. Cardiopulmonary Institute, Bad Nauheim, Germany;7. German Center for Cardiovascular Research, partner site Frankfurt, Bad Nauheim, Germany |
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| Abstract: | The micropylar apparatus (MA) in Ceratitis capitata (Diptera : Tephritidae) is a cone-like protrusion, 18 μm long, at the anterior pole of the egg, and exhibits about 40 follicle cell imprints externally. It consists of chorionic and vitelline membrane parts. The first contains at least a 3 μm wide micropylar canal; the tip of the MA is covered by a “tuft” and includes the micropyle, i.e. the entrance of the micropylar canal. The canal leads to the vitelline membrane part, where it forms a pocket. The sperm enters the oocyte by passing through the micropyle-micropylar canal-pocket route.At least 40 follicle cells participate in the formation of the micropylar apparatus. Two of these form 2 projections, which are tightly connected, and serve as a template for the formation of the canal and the pocket. Throughout their length, both projections have microtubules in parallel arrangement. During oogenesis, the remaining micropylar cells secrete the successive eggshell layers, i.e. the vitelline membrane, the wax layer, the innermost chorionic layer, the endochorion, and the exochorion. Towards the end of oogenesis, the 2 projections degenerate, and the canal becomes available for sperm passage. |
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