title: Fine structure of the chorion of Manduca sexta and Sesamía nonagrioides as revealed by scanning electron microscopy and freeze-fracturing.
abstract: The fine structure of Manduca sexta and Sesamia nonagrioides chorion was investigated by scanning electron microscopy and freeze-fracturing. In both species the mature chorion exhibits a complex ultrastructure on its outer surface, with a large number of aeropyles forming polygonal arrays. The micropyle is surrounded by a rosette of approximately 80 follicular cell imprints. Scanning electron microscopy of vertically ripped sections reveals that both chorions consist of two main layers: a trabecular layer closest to the oocyte and a lamellar layer. The technique of freeze-fracturing, utilizing single-sided and rotary shadowing, clearly shows that fibrils, approximately 3-4 nm in diameter, constitute chorionic lamellae in both species. The fibrils appear to have a 'beaded' structure, with a 2-3 nm axial periodicity. Freeze-fracturing also provides a direct visualization of the helicoidal arrangement of these fibrils for the formation of chorion supramolecular architecture.
authors.affiliation: Department of Biochemistry, Cell and Molecular Biology and Genetics, University of Athens, Panepistimiopolis, Athens 157.01, Greece.
authors.forename: C C
authors.initials: CC
authors.lastname: Orfanidou
authors.forename: S J
authors.initials: SJ
authors.lastname: Hamodrakas
authors.forename: L H
authors.initials: LH
authors.lastname: Margaritis
authors.forename: V K
authors.initials: VK
authors.lastname: Galanopoulos
authors.forename: J C
authors.initials: JC
authors.lastname: Dedieu
authors.forename: T
authors.initials: T
authors.lastname: Gulik-Krzywicki