G. Sahlen, ULTRASTRUCTURE OF THE EGGSHELL OF AESHNA-JUNCEA (L) (ODONATA, AESHNIDAE), International journal of insect morphology & embryology, 23(4), 1994, pp. 345-354
The eggshell of Aeshna juncea L. (Odonata : Aeshnidae) is described us
ing scanning and transmission electron microscopy. The vitelline envel
ope is homogenous. The endochorion is many-layered, the thickness of t
he sub-layers increasing from the inside and out. About 50 or more thi
n strata are arranged in a crystalline-like fashion, 0.17 mum thick, f
acing the vitelline envelope. This structure corresponds to the innerm
ost chorionic layer (ICL) reported from Drosophila melanogaster. About
70 thin, bilaminar crystalline-like strata associated with a more ele
ctron-dense material, appear between the endochorionic sub-layers near
the anterior end of the egg. The electron-dense exochorion is perfora
ted with thin canals opening in small pores on the surface. The filame
ntous pre-chorion substance forming the exochorion, previously reporte
d from Aeshna, is believed to form a paracrystalline region with a sph
erulite-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 wi
de. Corresponding passages in the vitelline envelope are believed to c
lose after fertilization. A standardized nomenclature for endophytic d
ragonfly eggs is proposed.