| Pteromalus puparum is the dominant endoparasitoid of Pieris rapae pupae, with a wide distribution and high control potential on this insect pest. The parasitoid has been studied throughout the world on its biology, ecology, artificial rearing as well as field releasing. However, reproductive physiology of the parasitoid has been still far from understood, though some aspects in this area had been studied recently in China. In this thesis, effects of several factors including diet, hormone, temperature and insecticide on the ovarian development and vitellogenesis of P. puparum were studied, with aims of providing guidelines for increasing its reproductivity, improving artificial-rearing techniques, and protecting the parasitoid in the field. 1 Ovarian development and vitellogenesisLength of ovariole in P. puparum, which was deprived of diets as well as host pupae at adult stage, increased significantly during the period from early pupal stage to 48 h after emergence, and then decreased gradually within the following 72 h. At early pupal stage, no egg chamber could be observed. At the late pupal stage, egg chambers had occurred, while yolk had not been deposited yet. The grade-I, grade-II and mature eggs began to be generated in the ovary at pharate adult stage, newly-emerged-adult stage and 12 h after emergence, respectively. In terms of egg dynamics, the grade-I egg was maintained at a high level during the period from pharate adult stage to 18 h after emergence. The grade-II egg peaked at 18 h after emergence, then decreased abruptly afterwards, and disappeared at 120 h after emergence. The mature egg, however, increased gradually between 12 and 48 h after emergence.Variance was found to some degree in the number of ovariole in P. puparum. In most of female adults (96.9%), ovary was composed of six ovariole, with three on each side. However, there were 0.4, 2.5 and 0.2% female adults whose ovaries were composed of 5, 7 and 9 ovarioles, respectively, with one ovariole more on one side than the other.Number of mature egg in the ovary was positively correlated with the length of hind tibia in thefemale adults aged 2, 6 and 10 d after emergence and feeding on 20% honey solution. That is, adults with longer hind tibias usually carried more mature eggs in the ovary.Lipoprotein in haemolymph and ovary of female P. puparum was analyzed at various stages using PAGE. The result showed that both vitellogenin (Vg) and vitellin (Vt) in this parasitoid could be classified as lipoprotein. The Synthesis of Vg was initiated at the pharate adult stage.Ultrastructures of fat body cell before and during vitellogenesis of the parasitoid were observed by electro microscope. During pupal stage, large amounts of protein granules and mitochondria were present in fat body cells, but no rough endoplasmic reticulum (RER) could be observed, indicating that fat body during this stage served predominantly as a place of storing proteins, with no secreting but great metabolizing activity. However, during the period from pharate adult stage to 5 d after emergence, large amounts of RER were present in fat body cells besides the mitochondria, and large lipid droplets also occurred. In other words, in this parasitoid, it was at the pharate adult stage that proteins began to be synthesized in large quantities. These findings supported the above result that the synthesis of Vg was probably initiated at pharate adult stage.Ultrastructures of follicle cell and oocyte in the ovary were also observed by electro microscope. In the newly formed egg chambers located at the top of ovary, space were present between follicle cells and oocytes, and there was no microvillus at the surface of either type of cell; in the oocytes, no Vt was deposited, while lots of lipid droplet accumulated. In the grade-I and grade II egg chambers, microvilli could be observed at both surface of follicle cell and oocyte, and besides lipid droplets lots of yolk granules accumulated in oocytes. In addition, yolk granules in grade-II chambers were obviously larg...
|
PDF Full Text Request