Licht- und elektronenmikroskopische Untersuchung von neurosekretorischen Zellen im Gehirn der Eintagsfliege Ephemera danica Müll. (Ephemeroptera: Ephemeridae)

In the brains of the males the amount of stained secretory material was nearly constant during the last four instars. In the females a decrease in this neurosecretory product in the last nymphal and subimaginal stage could be observed, followed by an increase in the imagines. In the final nymphal stage four types of neurosecretory cells (nsc) were found in the medial protocerebral cell group, showing differences in shape, size, and the contents of the cytoplasm, especially of the secretory granules. In addition to the medial nsc, some cells in the frontal part of the brain and in the deutocerebrum are described. They contain electron-opaque granules and probably have a neurosecretory function. The secretory product of the medial nsc is transported along the axons of the nervus corporis cardiaci 1 (ncc1), an unpaired nerve tract on the ventral side of the brain. Leaving the brain the ncc1 immediately enters the corpus cardiacum. Connections between secretory granules and neurotubuli point to an important role for the neurotubuli in the transport of secretory material.