Postembryonic development of the central complex and protocerebral bridge of Phormia regina meigen (diptera: Calliphoridae)

Abstract

The postembryonic development of the central complex and protocerebral bridge of Phormia regina Meigen was studied, using reduced silver nerve stains. The elements responsible for the development of the central body, ellipsoid body and protocerebral bridge are neuroblasts located in the larval cortex as isolated cells. These neuroblasts form the imaginal ganglion cells of these regions by a series of asymmetric and symmetric divisions. The central complex develops during the larval and pupal stages. The ellipsoid body appears first, followed later by the central body and ventral tubercles. Two isolated neuroblasts participate in the formation of the ellipsoid body, and 12 in the development of the central body. No neuroblasts were observed to participate in the development of the ventral tubercles. The central body develops from 14 nodules and cap of transverse fibers which later fuse to form the imaginal central body. The protocerebral bridge develops during the late larval and early pupal stages. It first appears as 2 nodules connected by a transverse commissure. Eight additional nodules are added to the bridge during development. These nodules fuse to form the imaginal protocerebral bridge. Each nodule is formed from the fibers of imaginal ganglion cells produced by one neuroblast. These same neuroblasts participate in the development of the central body.