Scanning electron microscope study on the egg chorion of silkmoth, Antheraea assamensis Helf. (Lepidoptera : Saturniidae)

Abstract

AbstractThe eggshell of Antheraea assamensis Helf. has a highly decorated chorion and its micropylar apparatus is situated at the cephalic end. Scanning electron microscopic investigation on the eggshells of A. assamensis reveals distinct patterns of structural elements viz., central cavity, micropylar rosette encircled the central cavity, and the aeropyles. The micropylar structures are at the anterior pole of the oval shaped eggs opposite to its side of distal pole. Centrally located central cavity leads into eight micropylar openings which further radiate down to the eight micropylar canals. The central cavity (5.28±0.21 μm in diameter) is encircled by a primary rosette of 16-18 cell imprints and each primary cell imprint measured 21.08±3.13 μm in length. The primary petal shaped cell imprints are followed by secondary and tertiary rows of cell imprints. Except the central cavity and micropylar rosette, the entire surface of the chorion is marked by a circular shell imprints which are boarded by aeropyles. Each cell imprint has 4-6 aeropyles and each aeropyle measured 1.06±0.01 μm in diameter. The aeropyles of A. assamensis are covered with a cup shaped like structures and the terminals of these structure has many finger like projections which may help to check the entry of pathogens or dust particles while taking the oxygen from the outside environment to the oocyte.