Proliferation and Differentiation: Two Sequential Stages of Proliferative Center Activity in Embryonic Mushroom Bodies of Three Orthopterans, Gryllus bimaculatus Deg., Acheta domesticus L., and Schistocerca gregaria Forsk. (Insecta: Orthoptera)

It is shown for the first time that, in three orthopterans (Gryllus bimaculatus, Acheta domesticus, and Schistocerca gregaria), the mushroom body proliferative centers pass two sequential stages of neurogenesis. At the first stage, they are built by symmetrically dividing proneuroblasts the activity of which augments the pool of the stem cells. At the beginning of the second stage, proneuroblasts transform into asymmetrically dividing mushroom body neuroblasts. Similarly to solitary neuroblasts, they give rise to daughter neuroblast and the ganglion mother cell, which divides symmetrically into two cells differentiating into the Kenyon cells. It is believed that the discovered course of neurogenesis in the embryonic proliferative centers of orthopteran mushroom bodies recalls the pattern described in the optic Anlagen of Drosophila melanogaster and other insects.