Male achiasmatic meiosis in Caraboidea (Coleoptera,Adephaga)

The meiotic process was studied in fifty-three species belonging to the caraboid families Bembidiidae (48). Trechidae (3), Pogonidae (1), and Harpalidae (1). Males show achiasmatic meiosis patterns of the Callimantis type. In females only early prophase stages were observed, that are similar to those of the males. The characteristics of this abnormal meiosis and its evolutionary and cytotaxonomic significance are discussed.     

“Nodules” in the achiasmatic meiosis of Bithynia (mollusca,prosobranchia)

In spermatocytes of Bithynia leachi and B. tentaculata, synaptonemal complexes with nodules in an achiasmatic meiosis were demonstrated for the first time by means of the spreading technique. The number and position of the nodules are different in each species and are independent of the length of the chromosomes. Although no crossing over occurs in Bithynia chiasma-like terminal connections of the chromosomes are preserved in diakinesis by the presence of the nodules. — Enzymatic treatments revealed information regarding their composition of alkaline proteins, RNA and DNA. In all proteolytic digestions the nodules more of less retain their position in the central region, while they disappear immediately if SCs are exposed to DNase. On the basis of the results a model of the composition and the function of nodules can be developed considering the concept of a lampbrush-organization of the chromosomes in early meiotic prophase.     

Revision of the genus Heliomantis Giglio-Tos 1915 (Insecta: Mantodea: Hymenopodidae)

Summary. The little-known flower mantis genus Heliomantis Giglio-Tos 1915 (Hymenopodidae) distributed in South and South-Eastern Asia is revised. All species are redescribed. New data on the morphology, distribution and ecology are given, and all known specimens are listed. The lectotype of H. elegans (Navás 1904) is designated. Due to highly divergent morphology, H. latipennis Werner 1930 from Sarawak, Borneo, is transferred to Werneriana n. gen., leaving the genus Heliomantis with the only species, H. elegans (Navás, 1904).     

Synaptonemal complexes,telomeric nucleoli and the karyosphere in achiasmatic oocyte meiosis of the carob moth

Synaptonemal complexes and telomeric nucleoli are involved in the spatial organization and regular distribution of homologous chromosomes in meiosis of the achiasmatic female carob moth. The bivalents are held together from zygotene to metaphase by the Synaptonemal complexes. These are attached to telomeric nucleoli which appear during early meiotic prophase and are unique to the oocyte. The telomeric nucleoli fuse during prophase and the chromosomes concentrate into a small karyosphere before prometaphase. During the final stages of prophase elements of the Synaptonemal complex are found in the periphery of the fibrillar region of the telomeric nucleoli.     

Synaptinemal complexes in primary spermatocytes of the mouse: the effect of elevated temperature and some observations on the structure of these complexes in control material

Summary In the present study the life cycle of synaptinemal complexes has been ascertained for C57B1 male mice. These complexes appear in stage VIII and disappear in stage IX of the subsequent cycle. In the mouse, pairing of single cores is prompt; after stage X single cores are very rare. The appearance of cores in leptotene in the normal mouse is almost synonymous with pairing. No prolonged or clearly defined stage has been seen in which all the cores are single. Likewise the disappearance of cores with pachytene of stage X is abrupt. It was observed that in heat-treated material the occurrence of cores is depressed. This is true (1) in cores that must have been preformed before the treatment was started — suggesting destruction of cores, (2) in cores formed during the progress of the experiment, and (3) in spermatocytes originating from cells that must have been subjected to heat several cell generations before they were observed. In all cases asynapsis is expressed as a depression of the total core number as well as a percent increase in the unpaired cores. The phenomenon of induced asynapsis is suggested to reflect a change in outer hydrogen bonds of the respective chromosomes.This work was performed under the auspices of the U.S. Atomic Energy Commission.Dedicated to Professor Franz Schrader on the occasion of his 70th birthday.     

Karyotype analysis and achiasmatic meiosis in pseudoscorpions of the family Chthoniidae (Arachnida: Pseudoscorpiones)

Karyotypes of pseudoscorpions (Arachnida, Pseudoscorpiones) are largely unknown. Here we describe for the first time karyotypes of the suborder Epiocheirata, represented by 9 European species of two genera of Chthoniidae, Chthonius and Mundochthonius. Diploid chromosome numbers of males range from 21 to 37. Karyotypes of both genera differ substantially. Acrocentric chromosomes predominate in karyotypes of the genus Chthonius, whereas M. styriacus exhibits a predominance of metacentric chromosomes. These differences suggest that the two genera belong probably to distant branches of the family Chthoniidae. It is proposed that karyotype evolution of the genus Chthonius was characterised by a reduction of chromosome numbers by tandem and centric fusions as well as gradual conversion of acrocentric chromosomes to biarmed ones, mostly by pericentric inversions. A tendency towards reduced chromosome numbers is evident in the subgenus Ephippiochthonius. All species display X0 sex chromosome system that is probably ancestral in pseudoscorpions. The X chromosome exhibits conservative morphology. It is metacentric in all species examined, and in the majority of them, a subterminal secondary constriction was found at one of its arms. In contrast to chthoniids, secondary constriction was not reported on sex chromosomes of other pseudoscorpions. Analysis of prophase I chromosomes in males revealed an achiasmatic mode of meiosis. Findings of the achiasmatic meiosis in both genera, Chthonius and Mundochthonius, indicate that this mode of meiosis might be characteristic of the family Chthoniidae. Amongst arachnids, achiasmatic meiosis has only been described in some scorpions, acariform mites, and spiders.     

Meiotic association and segregation of the achiasmatic giant sex chromosomes in the male field vole (Microtus agrestis)

Controversy exists regarding the meiotic behaviour of the giant sex chromosomes during spermatogenesis in the field vole, Microtus agrestis. Both univalents and bivalents have been observed between diakinesis and metaphase I. These differences seem to be dependent on the technique used. The present study employs electron microscopy of serially sectioned testes tubules and light microscopy of microspread preparations to re-examine the behaviour of sex chromosomes during meiosis. In microspreads, about one-third of the early pachytene nuclei examined showed end joining of the X and Y axes. The longitudinal heterogeneity of the chromosomes in the form of axial thickenings allowed the detection of two different end-joining patterns. In the remaining early pachytene cells as well as in all mid to late pachytene cells seen, the X and Y axes had, though near to each other, no contact in the form of a synaptonemal complex. If a synaptonemal complex is a prerequisite for genetic exchange, the sex chromosomes in M. agrestis males must be achiasmatic. The analysis of serial sections through an early pachytene and a late prophase I nucleus with the electron microscope revealed that the sex chromosomes occupied a common area. By metaphase I, the centromeres of the X and Y were oriented towards opposite spindle poles while the chromosomes remained attached to one another by their distal segments at the level of the metaphase I plate. As a consequence of the large size of the sex chromosomes their centromeres lay close to the spindle poles. In anaphase I the sex chromosomes maintained their metaphase position until the autosomes approached the spindle poles. During autosomal migration a medial constriction developed where the sex chromosomes were mutually associated, the X and Y became separated, and joined the autosomes. In metaphase II the chromatids of the sex chromosomes lay side by side and exhibited a delayed separation in the subsequent anaphase. It is suggested that heterochromatin, which represents a major part of both sex chromosomes, plays a role in the association of the two achiasmatic sex chromosomes in metaphase I and in the delayed separation of the chromatids of the sex chromosomes in anaphase II.Dedicated to Prof. C.-G. Arnold (Erlangen) on the occasion of his 60th birthday     

Light-producing organs in Keroplatus tipuloides Bosc and K. reaumuri pentophthalmus Giglio-Tos (Diptera : Mycetophilidae)

In this paper, the problem of the luminescence in larvae and pupae of mycetophilid dipterans has been studied. Keroplatus tipuloides Keroplatus reaumuri pentophthalmus and Cerotelion lineatus (Diptera: Mycetophilidae) have been examined by electron microscopy and biochemical methods. We demonstrate that the luminescence in Keroplatus is due to particular proteinaceous granules contained in the fat body of mature larva and pupa; it disappears in the adult, which is devoid of granules. Granules contain 3 major polypeptide chains, and are absent from the closely related genus Cerotelion, which has no luminescent larvae or pupae.     

Ultrastructure and behavior of the achiasmatic,telosynaptic XY pair of the sand rat (Psammomys obesus)

The behavior of the X and Y chromosomes in somatic and testicular cells of the sand rat (P. obesus) has been investigated with light and electron-microscope procedures. The Y chromosome has been identified as the fourth longest of the complement, both by C-banding and by its meiotic behavior. The X chromosome is the longest of the complement and carries two major C-heterochromatic blocks, one in the distal part of the long arm and the other forming most of the short arm. During presynaptic stages in spermatocytes, separate C-heterochromatic blocks, representing the sex chromosomes, are observed in the nuclei. An XY body is regularly formed at pachytene. During first meiotic metaphase the X and Y chromosomes show variable associations, none of them chiasmatic. Second meiotic metaphases contain, as in other mammals, a single sex chromosome, suggesting normal segregation between the X and the Y. — Electron microscopic observations of the autosomal synaptonemal complexes (SCs) and the single axes of the X and Y chromosomes during pachytene permit accurate, statistically significant identification of each of the largest chromosomes of the complement and determination of the mean arm ratios of the X and Y axes. The X and Y axes always lie close to each other but do not form a SC. The ends of the X and Y axes are attached to the nuclear envelope and associate with each other in variable ways, both autologously (X with X or Y with Y) and heterologously (X with Y), with a tendency to form a maximum number (four) of associated ends. Analysis of 36 XY pairs showed no significant preference for any single specific attachment between arm ends. The eighth longest autosomal bivalent is frequently partially asynaptic during early pachytene, and only at that time is often near or touching one end of the X axis. — It is concluded that while axis formation and migration of the axes along the plane of the nuclear envelope proceed normally in the X and Y chromosomes, true synapsis (with SC formation) does not occur because the pairing region of the X chromosome has probably been relocated far from the chromosome termini by the insertion of distal C-heterochromatic blocks.     

Kinetics of spermatogenesis in the white-lipped peccary (Tayassu pecari)

This study aimed to characterize the stages of the seminiferous epithelium cycle by the tubular morphology method, and to determine the number of differentiated spermatogonia generations in the adult white-lipped peccary. Twenty adult white-lipped peccaries, obtained from commercial slaughterhouse, were used. Fragments of the testicular parenchyma were fixed in 3% glutaraldehyde and embedded into a methacrylate resin. The number of germ and Sertoli cells was estimated by the analysis of cell populations in 50 transversal sections of seminiferous tubules in different stages of the cycle. The tubular morphology method allowed the identification of cellular associations characteristic of the eight stages of the seminiferous epithelium cycle in white-lipped peccaries. The results showed the presence of six generations of differentiated spermatogonia in white-lipped peccaries, and that the cell composition of the eight stages of the seminiferous epithelium cycle in this species is very similar to that described for collared peccaries.     

Somatic Embryogenesis in Brassica nigra (Koch)

Four genotypes of Brassica nigra were tested for their abilityto produce somatic embryos in vitro. Seedling-derived hypocotylexplants cultured in MS medium with p-chlorophenoxyacetic acid,-naphthaleneacetic acid and adenine gave rise to embryos thatcould germinate into seedlings with a high frequency on transferto medium containing benzylaminopurine riboside and p-chlorophenoxyaceticacid. Ebryogenesis was highest in leaf explants followed bystem and hypocotyls. Comparison of the embryogenic responseof hypocotyl segments differing in age indicated an increasein the frequency of response with increasing age of the explants.However, germination of embryos into seedlings declined withincreasing age of the explant. Embryogenesis was higher in MSmedium compared to five other media with similar growth regulatorcomposition. Genotypic differences exist for frequency of embryogenesisand subsequent maturation into seedlings. Key words: Brassica nigra, somatic embryogenesis, growth regulators, plant regeneration