ALBERT

Notes: Summary The development of the telotrophic ovary in the Staphylinid beetle,Creophilus maxillosus was examined. Cells, termed chordoblasts were identified in the germarium of 1-day-old pupae. Each of the chordoblasts undergoes a series of synchronous mitoses. Owing to the precise control of the cleavage plane, which is vertical to the long axis of the ovariole, each of the chordoblasts gives rise to a linear chain of sibling chordocytes. Extra DNA synthesis within each sibling string is usually limited to the most posterior chordocyte only, this being an oocyte progenitor. Divisions of the oocyte progenitor are differential mitoses in which the extra DNA material is transported preferentially towards the posterior pole of the spindle. As extra DNA synthesis and preferential segregation of this material result in gradual increase of this DNA in the nuclei of oocyte progenitors, cytokinesis of these cells becomes highly unequal, the larger of the two cells produced at each differential mitosis being as a rule the posterior cell, i.e. the oocyte progenitor of the next cell generation. As a resul of the series of differential mitoses each chordoblast gives rise to a number of nurse cells and only one definitive oocyte. It is suggested that somatic prefollicular tissue plays a decisive role in oocyte determination in the Coleopteran telotrophic ovary.

Notes: Summary A new type of composite eggs was found in the non-paedogenetic gall midgesMikiola fagi andRhabdophaga rosaria. Composite eggs of this type contained two or three nurse chambers and one egg chamber with one oocyte nucleus. In all composite eggs examined only one nurse chamber developed normally, while the others, regardless of their number and position within a composite egg, were arrested in their growth. It is assumed that the arrested nurse chambers, contrary to normally developing ones, are deficient in generative nuclei and thus are derived exclusively from mesodermal cells.

Notes: Summary Larvae of Dasyneura urticae parasitized by an unidentified species of the Platygasteridae were found to contain giant polyploid nuclei of a polytene type. Comparison of polytene chromosomes of the giant nuclei with those of salivary-gland nuclei of D. urticae has shown that the giant nuclei are derived from the host nuclei, polyploidy and polyteny of these nuclei being, therefore, induced by the parasite.

Notes: Summary The basal reservoir nuclei of the full grown larvae of Dasyneura urticae contain four typical polytene chromosomes. The gland proper nuclei have a reticular structure and are polyploid. Examination of the proper gland nuclei in full grown larvae as well as in young larvae has shown that the polyploidy of these nuclei is brought about by progressive splitting of the polytene chromosomes into numerous fibrils of a low degree of polyteny (oligotene fibrils). The individual oligotene fibrils after separation from one another do not undergo any significant shortening. The progressive splitting of the polytene chromosomes is not a synchronous process, that is, it begins in different chromosomes of the same nucleus at different stages of their development. This process is superimposed on the further endomitotic growth of the polytene chromosomes.

Notes: Abstract In the oogenesis of the gall midge Oligotrophus schmidti, a material assumed to be precursor material of the first maturation division spindle appears in the middle area of the early diplotene nucleus in close association with the chromosomes. At the beginning of the growth stage of the oocyte this material together with the chromosomes is transported as a characteristic ring-shaped body toward the nuclear membrane. Having approached the nuclear membrane the ring material spreads all over its inner surface. Next, it differentiates into a continuous cortical layer of a non-chromosomal material and the chromosomal vesicles. The cortical layer, about 1μ, thick, is appressed tightly to the inner surface of the nuclear membrane, being delimited against the nuclear sap by a membrane-like boundary. At the end of diakinesis the chromosomes congregate in the middle area of the nucleus, and at the same time the spindle organizing activity of kinetochores begins. At the early stages of its development the spindle is a compound structure, consisting of a number of individual spindles, each of them being organized by a separate group of chromosomes. Changes in the structure of the cortical layer before and during prometaphase spindle formation are interpreted to indicate that the precursor material of the spindle is dissolved and diffuses into the nuclear sap. The nuclear membrane and the remnants of the cortical layer do not disappear until late prometaphase when the process of spindle formation is nearly completed.

Notes: Abstract InCecidomyiidae the number of trophocytes derived from the somatic tissue of the ovary and forming nutritive chambers of egg follicles is variable. The regulation of growth of the whole nutritive chambers and of the nurse nuclei was investigated in two species of the gall midges,Mikiola fagi andBoucheella artemisiae, at two different stages of the egg follicle development during the second period of the oocyte growth. The volume of a nutritive chamber is correlated with the size of the egg follicle as a whole and is not dependent on the number of nurse nuclei it contains. The total volume of nurse nuclei at each stage under investigation was found to have a constant value which is independent of their number. It was established that the growth of the nurse nuclei takes place through endomitosis, and that at a given stage of the egg follicle development the constant value of the total volume of the nurse nuclei reflects the constancy of degree of their total polyploidy. The results obtained indicate that at the early stages of the egg follicle development the rates of growth of the nurse nuclei and of the whole nutritive chambers in the egg follicles differing with respect to the number of their nurse nuclei must be different; the greater the number of nurse nuclei in a given nutritive chamber the slower the rate of growth of the chamber and their nuclei. As a result of this differential rate of growth the volumes of the nutritive chambers and total volumes of nurse nuclei reach at a certain stage of the egg follicle development certain values common for all egg follicles, irrespective of the number of the nurse nuclei they contain. Beginning with this stage the dependence between the endomitotic activity of the nurse nuclei and the rate of growth of the whole nutritive chamber on the one hand, and the number of the nurse nuclei in the chamber on the other, evidently disappears. The available evidence supports the hypothesis that in the egg follicle ofCecidomyiidae the growth regulation of nurse nuclei and, indirectly, also of whole nutritive chambers results from developmental interrelationships between the oocyte and the nutritive chamber, and that the oocyte plays a leading role in this process. In view of a syncytial character of the nutritive chambers inCecidomyiidae and distinctly expressed asynchrony of the growth-duplication cycles of nurse nuclei belonging to a given chamber it is concluded that the control mechanism for DNA synthesis and endomitosis in nurse nuclei must possess the property of a rapid switch. Processes of the growth regulation of the nurse nuclei are discussed in connection with the role of the nutritive chamber in production of RNA and its supply to the growing oocyte. It is suggested that in the egg follicles ofCecidomyiidae there exists a complex interrelationship between the control mechanism for DNA synthesis and endomitosis in the nurse nuclei and the synthetic processes regulated by the supply of the growing oocyte with RNA produced by the nuclei of the nutritive chamber.

Notes: Summary 1. Female somatic nuclei of Mikiola fagi contain only diploid sets of S-chromosomes (8 S), while germ-line nuclei have 24 chromosomes (8 S-chromosomes + 16 E-chromosomes). 2. In oogenesis only S-chromosomes form chiasmatic bivalents, while E-chromosomes occur as univalents. At prometaphase, and immediately before the first maturation division, the E-chromosomes may temporarily form associations of two, three or four, a contact which is of the somatic pairing type. 3. At metaphase, E-chromosomes are simultaneously eliminated from the spindle. This phenomenon is probably the result of a temporary inactivation of the kinetochores of E-chromosomes and may be interpreted as proof of the existence of transverse elimination forces in the spindle. 4. The E-chromosomes eliminated from the spindle aggregate as a rule in one or, less frequently, two or three groups, each of which forms then its own spindle. 5. Shortly before the first maturation division E-chromosomes rejoin the spindle with the bivalents. 6. During the first maturation division, which is a reduction division for S-chromosomes, the anaphase movement of E-chromosomes is greatly delayed. E-chromosomes, owing to the strong anaphase elongation of the spindle, are passively distributed on its surface. 7. There is no interphase between the first and second maturation division. Towards the end of anaphase I two small spindles of the second meiotic division are formed at the spindle poles, each of which contains only one haploid set of S-chromosomes. 8. Equational splitting of E-chromosomes occurs mostly when the S-chromosomes are at metaphase of the second maturation division. The anaphase movement of daughter E-chromosomes begins without prior formation of a metaphase plate. The position of E-chromosomes on the spindle surface seems to have no influence on the separation of the daughter chromosomes and their migration to the opposite poles of the first meiotic spindle. The anaphase movement of the daughter E-chromosomes, which occurs at the time when S-chromosomes undergo the second maturation division, leads to the formation of two groups each containing 16 chromosomes. In the early stages of this movement, each of the daughter E-chromosomes is oriented towards the pole not with its kinetochore but with one of its ends. Thus, the bivalent S-chromosomes undergo two maturation divisions whereby their number is reduced, while the univalent E-chromosomes undergo only one equational division. 9. It is postulated that the egg nucleus is formed as the result of a fusion between one haploid set of S-chromosomes and one set of E-chromosomes. As it is not known whether the eggs develop without fertilization, the establishment of the diploid number is open to discussion. Probably, in the Polish populations of the species with a very low percentage of males, the development starts with the fusion of the egg-nucleus with a haploid set of S-chromosomes whereby the number is raised from 20 to 24. 10. The evolution of cecidomyiid oogenesis is discussed. The modifications of oogenesis observed in the subfamily Cecidomyiinae are interpreted as mechanisms preventing the decrease of the number of univalent E-chromosomes during maturation divisions. 11. During prophase a special nuclear material accumulates around the chromosomes grouped inside the nucleus and leads to its characteristic differentiation into an interior part containing both S- and E-chromosomes and an exterior zone of nuclear sap. In prometaphase the first meiotic spindle arises from material localized in the interior part of the nucleus. The problems of the origin of the spindle-forming material as well as the formation of spindles by the E-chromosomes eliminated into the cytoplasm are discussed.