Egg chamber development in the onion fly, Hylemya antiqua (Meigen) (Diptera: Anthomyiidae)

Abstract

The development of the egg chambers in the ovary of the onion fly, Hylemya antiqua (Meigen), is divided into 10 stages beginning with the first signs of differentiation in the germarium up to the mature egg. Mainly 2 groups of criteria have been used to indicate the different stages: for the younger egg chambers histological criteria, especially concerning the appearance and dispersion of the chromatin in the trophocyte nuclei, have been formulated; the older stages have been defined by means of characters which are visible with a normal binocular microscope. In this way the development of the older egg chambers can be used in standard methods for several purposes in mass rearing, field trials, etc. The most important features of the developmental stages are: Germarium: no visible differentiation of the germ cells. 1. Stage 1: beginning of differentiation and separation from the germarium. 2. Stage 2: egg chamber separated from the germarium by epithelial cells; strand and ribbon-like chromatin structures in nuclei of the trophocytes. 3. Stage 3: large transformations in the chromatin structures of the trophocyte nuclei. 4. Stage 4: increasing morphological uniformity of chromatin structures; beginning of yolk formation. 5. Stage 5: egg chamber distinctly ellipsoidal; oocyte of the same size as the trophocytes. 6. Stage 6: oocyte larger than the trophocytes. 7. Stage 7: oocyte 1 4 − 1 2 of the total egg chamber volume. 8. Stage 8: oocyte 1 2 − 3 4 of the total egg chamber volume. 9. Stage 9: oocyte larger than 3 4 of the total egg chamber volume. 10. Stage 10: mature egg.