Polygonal patterns on eggshells of giant egg mutant and large eggs induced by 20-hydroxyecdysone in Bombyx mori

The polygonal network patterns, i.e. the secretory surface imprints produced by the follicular epithelial cells, on the lateral side region of eggshell in Bombyx mori were observed by scanning electron microscopy and differential interference contrast microscopy in order to characterize the giant egg (Ge) mutant and large eggs induced by the injection of 20-hydroxyecdysone into pupae. The area of each polygon was smaller in Ge but larger in the induced large eggs than in the normal eggs. The polygon number per unit area was much higher in Ge than in the normal eggs, but the induced large eggs exhibited the same number as the normal eggs. These results indicate that Ge is a mutant in which the number of the follicular epithelial cells is increased, whereas injected 20-hydroxyecdysone promoted hypertrophy of the follicle cells during choriogenesis.