Ultrastructure of Ovarian Follicular Epithelium During Oogenesis in Lucilia silvarium (Diptera: Calliphoridae)

Abstract

Lucilia silvarium (Diptera: Calliphoridae) is one of the medically important blowflies. The ovaries of this fly were examined at different stages using a light microscope and transmission electron microscopy. The gonadal cycle is elucidating eight stages of development. The ovaries are made up of ovarioles, each ovariole composed of a successive number of developing follicles. These follicles are arranged in the order that the younger follicles lie closer to the germinal cells, while the mature follicles lie posteriorly. The younger follicle consists of the germ cells enveloped by a single layer of epithelium. The germ cells differentiate into nurse cells and the oocyte. The follicular epithelium diversified itself during oogenesis and accommodate themselves to fit the increasing volume and growing of the oocyte. In the previtellogenic oocyte, the ovariole sections are spherical and show cubical follicular epithelial cell layer surrounding the oocyte and the nurse cells. The vitellogenic oocyte, has follicular epithelium elongated to become columnar surrounding the developing oocyte and squamous enclosing the nurse cells. In post vitellogenic oocyte, the follicular epithelial cells become very thin and hardly observed and the eggshell formation is completed.