| Abstract: | The embryonic cytodifferentiation of Clitumnus midgut occurs very late when compared to that of other tissues in the embryo. It proceeds from hemolymph towards the yolk, first at the level of the muscular–connective tissue sheath, by the appearance of myofilaments in external–then internal–muscle fibers. In the gut epithelium, cytodifferentiation begins with the appearance of infoldings of the basal membranes of the cells. Then, microvilli and continuous junctions form at the apices of the cells. Microvilli appear in crypts, which seem to represent localized dilatations of intercellular spaces. At the level of these crypts, continuous junctions are formed somewhat later than are microvilli. This midgut differentiation coincides with deposition of the third embryonic (first larval) cuticle, and with a high titer of ecdysteroids. |
