ULTRASTRUCTURE OF THE EGGSHELL OF AESHNA-JUNCEA (L) (ODONATA, AESHNIDAE)

The eggshell of Aeshna juncea L. (Odonata : Aeshnidae) is described using scanning and transmission electron microscopy. The vitelline envelope is homogenous. The endochorion is many-layered, the thickness of the sub-layers increasing from the inside and out. About 50 or more thin strata are arranged in a crystalline-like fashion, 0.17 mum thick, facing the vitelline envelope. This structure corresponds to the innermost chorionic layer (ICL) reported from Drosophila melanogaster. About 70 thin, bilaminar crystalline-like strata associated with a more electron-dense material, appear between the endochorionic sub-layers near the anterior end of the egg. The electron-dense exochorion is perforated with thin canals opening in small pores on the surface. The filamentous pre-chorion substance forming the exochorion, previously reported from Aeshna, is believed to form a paracrystalline region with a spherulite-like configuration comprising the inner half of the layer. At the anterior end of the egg, the endo- and the exochorion are anchored to each other in a regular manner. The micropylar chutes are 5 mum wide. Corresponding passages in the vitelline envelope are believed to close after fertilization. A standardized nomenclature for endophytic dragonfly eggs is proposed.