Gonotrophic development in Oestrus ovis (Diptera : Oestridae)

Microanatomical characteristics and the size of the ovaries of Oestrus ovis L. during development were related to the intrapuparial-phenological stadi a. Mature 3rd instars were collected from the head cavities of slaughtered goats, and pupae were reared under laboratory conditions. The length of fre shly dissected ovaries and follicles were measured daily after pupal-adult apolysis to emergence. Ovarian tissue was stained using the PAS-Picroindigo carmine techniques. Oocyte development was classified according to a six-st age scale previously used in oestrid species. Shortly after pupal-adult apo lysis, the single primary follicle is still unseparated from the germarium. In early white-eyed pharate adults, the primary follicle of stage 1 separa tes from the germarium, the nurse cells and oocyte are surrounded by a laye r of cuboidal follicular cells, and the remaining oogonia degenerate. Oocyt es in stage 2 initiate yolk deposition becoming ovoid, and this occurs when pharate adults have white-yellow to orange eyes. Oocytes in stage 3 are ma inly vitellogenic, during the orange to red-eye stage. In stage 4, oocytes complete vitellogenesis and nurse cells degenerate when pupae achieve 90-96 % of development. Mature oocytes of stage 5 can be found at emergence. Ovar ies and ovarioles increase in size because of yolk deposition. O. ovis begi ns oogenesis as pharate adults, whereas vitellogenesis occurs during 55-96% of pupal development. Females emerge with one lift-long complement of eggs ready to be fertilized, similar to other species of the Family Oestridae.