ABSTRACT
This chapter examines the effects of two selected test agents, i.e., 20-hydroxyecdysone and cytochalasin B, on specific oogenetic events, such as pulsation of oocyte nuclei, follicle formation, and synthetic ovarian activities. Observation and manipulation of oogenetic processes have been highly facilitated by the elaboration of a method of culturing ovaries and follicles in vitro, i.e., in hemolymph obtained from sterilized larvae. As compared to oogenesis in other insects with polytrophic-meroistic ovarioles, oogenesis in pedogenetically reproducing Heteropeza pygmaea larvae is highly modified. The gall midge H. pygmaea is a remarkable insect, as it can reproduce in the larval stage. This reproductive mode is called pedogenesis; it is linked to viviparity and parthenogenesis. At the time of explantation and start of the cultures the H. pygmaea ovary contains 15 to 20 oocyte-nurse chamber complexes and a large number of prefollicle cells. The oocyte nucleus itself is usually synthetically inactive, but exceptions concerning specific oogenetic stages or species may occur.
