Structure of the trophic chamber (germarium) in virginoparae of the vetch aphid,Megoura viciae Buckton (Homoptera : Aphididae) |
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| Institution: | 1. State Key Laboratory of Grassland Agro-Ecosystems, College of Pastoral Agricultural Science and Technology, Lanzhou University, Lanzhou, Gansu 730020, People''s Republic of China;2. Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture, People''s Republic of China;3. National Demonstration Center for Experimental Grassland Science Education (Lanzhou University), Lanzhou, Gansu 730020, People''s Republic of China |
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| Abstract: | The structure of the germaria in the ovaries of the viginoparous morph of the vetch aphid, Megoura viciae Buckton (Homoptera : Aphididae) is described and compared to other insects, including aphids. Each consists of a syncytium of trophocytes and resting oocytes arranged around a trophic core. Trophocytes contain mitochondria, ribosomes, vacuoles and some membrane-bounded material. Golgi complexes were not found. Each trophocyte has a single spherical nucleus with “nuage-like” material confluent between nucleoplasm and cytoplasm via numerous nucleopores. The surrounding monolayer of somatic epithelial sheath cells are bounded externally by an acellular tunica propria. These cells continue into the prefollicular tissue in the base of each germarium. Cells from the prefollicular tissue envelop each oocyte as it is released from a germarium. The “previtellogenic” growth phase of oocytes is relatively short, and vitellogenesis is absent. Virginoparae are reproductively precocious, and newly born larvae have up to 3 oocytes undergoing development in their anterior ovarioles. Interovariole ovulation is asynchronous within, and partially synchronous between, the 2 ovaries. |
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