Electron Microscopic Studies on the Posterior Silk Gland of Silkworm, Bombyx mori (III)

Development of Posterior Silk Gland of Silkworm during the 4th Instar Larvae

Abstract

OsO₄ was not effective for the preservation of the posterior silk gland of the 4th instar larvae, while glutaraldehyde fixation was essential for this purpose. Glutaraldelyde fixation, post fixation with OsO₄ and block staining with uranium acetate were conventionally used throughout this experiment.
Structure of the cytoplasm of the posterior silk gland in the early stage of the 4th instar larvae is very similar to the 2nd or the 3rd stage of the 5th instar larvae, well developed vesicular or tubular rough endoplasmic reticulum with enlarged cavities and the Golgi vacuoles being abundantly observed. Just befor or at the begining of the 4th moulting, however, membrane components of rough endoplasmic reticulum, outer nuclear envelops, Golgi membranes, inner and outer mitochondrial membranes, etc disappear, while inner nuclear envelops and cell membranes remain unchanged. At the end of the 4th moulting these membranes reappear. Biological significance of this disappearance of these membranes during the moulting cycle of the silkworm was discussed.