Tens versus Four: Two Generations of Neural Progenitors in the Developing Mushroom Bodies of Muscina prolapsa Harris (Diptera, Muscidae)

Neurogenesis in the mushroom bodies was studied throughout the larval and pupal development of Muscina prolapsa. The existence of two generations of neural progenitors in the mushroom bodies of insects was established for the first time. Each larval mushroom body has four neuroblasts that divide as type I neuroblasts, producing a daughter neuroblast and a ganglion mother cell. The latter divides symmetrically into two cells that differentiate into Kenyon cells. In the young pupae, 8–11 cells surrounding each neuroblast of the mushroom body and morphologically indistinguishable from ganglion mother cells grow in size and transform into secondary neuroblasts, which repeatedly divide asymmetrically into a daughter secondary neuroblast and a typical ganglion mother cell. Divisions of secondary neuroblasts continue from the 3rd to the 7th day after puparium formation, and during the 7th day, secondary neuroblasts die massively through apoptosis. The fate of four neuroblasts of the larval mushroom body remains obscure.