Light and electron microscopic studies on the development of the ovaries of Culex pipiens quinquefasciatus (Say) (Diptera: Culicidae)

Abstract

Christopher's stages of ovarian development are redefined in Culex pipiens quinquefasciatus to provide a more useful description of mosquito physiology. During this ovarian development, seven growing stages of the oocyte are observed in the adult stage. Two distinct periods of egg follicle growth, the previtellogenesis and vitellogenesis, are seen first. The gradual increase in the oocyte size during these phases is attributed to yolk deposition. During vitellogenesis, the oocyte and nurse cell nucleus are similar in size (stage I). Then, the oocyte enlarges and occupies one third of the egg follicle, while the nurse cell (NC) occupies the remaining two thirds. At this phase, the yolk granules (stage III) enlarge, occupying about half of the egg follicle, while the NC contain the other half (stage IV). An increase and accumulation of yolk granules leads to the filling of about three fourths of the egg bulk and makes the oocyte nucleus hardly visible during stage V. The oocyte undergoes a remarkable growth, occupying nine tenth of the length of the follicle in stage VI. Stage VII corresponds to a mature cigar-shaped egg and contains two kinds of yolk globules: a large one and a small one. The oocyte and the NC at all stages are surrounded by a single layer of epithelial cells which increase in number and form the vitelline membrane and the chorion. The mitochondria in the NC, oocyte, and follicular epithelium appear in light microscopy as granules of different sizes. The Golgi apparatus appears in different sizes and shapes, since in the early stages of development, it is restricted to the perinuclear zone. When the development proceeds, it enlarges in size, spreads over the whole cytoplasm, and participates in the formation of the yolk.

Ovarian Development of House Fly (Musca domestica L.) (Diptera: Muscidae)

“…In future stages, the follicle develops slower and packed with yolk granules which become considerably bigger and opaque. These observations were consistent with those [45] and with [38] for Culex pipiens quinquefasciaatus. [46] Indicated that the epithelial follicicle cells of Mansonia species in young follicle are cuboidal in shape, when the follicle lengthened, the epithelial cells increasingly shrinks in thickness.…”

Studies on the Development of the Ovaries of the Malaria Mosquitoes(Anopheles pharoensis)

“…The follicle was partially separated from the germarium and the oocyte was not surrounded by epithelium. Similar observations were reported by Detinova [25], Clements and Boocock [20] for Aedes aegypti, Culex pipiens quinquefasciatus, and Anopheles gambiae and by Adham et al [21] for C. P. quinquefasciatus.…”

“…The latter culminated in the final formation of the mature egg. Thus, a single large blood meal was normally sufficient to trigger the completion of ovarian development as was reported by Kawai [13], Bellamy and Bracken [14], Abdel-Ghaffar [24] for C. molestus, Carnevale et al [17], Lea et al [18] and Adham et al [21] for C. pipiens quinquefasciatus. However, Christophers [1] reported that the progressive changes in the ovary and ovarioles of mosquitoes may pass only through five phases.…”

“…aegypti, C. p. quinquefasciatus and Ae. gambiae, and by Adham et al [21] for C. P. quinquefasciatus.…”

“…Some investigators presented evidence which made it clear that maturation of the oocytes in mosquitoes results from a connection between the process of blood digestion and the development of the ovaries. Important progress has been achieved by Christophers [1,2], Nicholson [3], Nath [4], Woke [5], Beklemishev [6], Detinova [7,8], Polovodova [9], Macan [10], Clements [11], Volozina [12], Kawai [13], Bellamy and Bracken [14], Shalaby [15], Watts and Smith [16], Carneval et al [17], Lea et al [18], Ahmed [19], Clements and Boocock [20] and Adham et al [21]. The description of the sequence of the ovarian development in the malaria mosquito An.…”