Characteristics of the karyotype and early meiosis of two males of the cryptic “western” form of the viviparous lizard (Zootoca vivipara Lichtenstein, 1823) (genus Zootoca Wagler, 1830) with multiple sex chromosomes (female Z1Z2W/Z1Z1Z2Z2 male) were examined. The data obtained were compared with 1) those of the males of the same cryptic form from other locality, with 2) those of the males of other cryptic form also possessing the multiple sex chromosomes and with 3) those of the species of closely related genus Takydromus Daudin, 1802 with simple sex chromosomes, ZW/ZZ. Multiple sex chromosomes may influence meiosis and play a role in isolation. The males of cryptic western form of Z. vivipara studied revealed the karyotype with 36 acrocentric chromosomes (2n=36A). In early meiosis the spreading of synaptonemal complexes (SC) of the bivalents of these males were obtained and analyzed. Eighteen SC were observed, including SC of the Z1Z1 (pair 6) sex chromosomes. Characteristics of SC are compared with the number and the shape of bivalents and chromosomes at the diakinesis and metaphase 11 stages of the meiosis of the males from other population and with those in the other cryptic Russian form of the species. Comparative analysis of two cryptic forms has demonstrated some differences in the morphology of SC Z1Z1 sex chromosomes at the early stages of prophase 1 of meiosis (the late zygotena – the middle pachytene stages). However both the SC of sex chromosomes and SC of all remained chromosomes were fully synapted. All 18 bivalents were regular segregated forming haploid spermatocyte II with18 chromosomes, including two sex chromosomes (n=8, Z1Z2) Thus characteristics of karyotype and early meiosis of the males of western form belonging to different localities are fully coincident with those of Russian cryptic forms of Z. vivipara with multiple sex chromosomes as well. However, these features were differed from those for the species of the closely related genus Takydromus with simple sex chromosome system (ZW) where some disturbances in the course of mitoses and meiosis were observed. The results are in agreement with those suggested previously about the genomic factor(s) stabilizing the meiosis and the maintenance of multiple sex chromosome in the different cryptic forms of complex Z. vivipara.

This paper is a revision of the original description of the karyotype of the sable Martes zibellina. It presents data on the mitotic metaphase chromosomes of the female and male of this species and a comparison of their sets with those of closely allied species in the genus Martes. Additionally, a description of the synaptonemal complex (SC) is provided in the early to middle prophase of meiosis in the sable spermatocytes. Comparative analysis confirmed the stability and similarity of the main cytogenetic parameters of sables and martens (2n = 38, NFa = 64–68, X is the average submetacentric and Y is the smallest meta-, submeta-, or acrocentrics). A slight polymorphism associated with the representation of one- or two-armed small elements of the diploid set of chromosomes is revealed. These characteristics are of little use for the development of the intraspecific taxonomy of the sable, but can be useful in determining phylogenetic relationships at the species and generic levels, as well as to identify the consequences of natural hybridization of allied species in the genus Martes.

This brief review is focused on the viviparous lizard Zootoca vivipara (Lichtenstein, 1823), of the family Lacertidae, which possesses female heterogamety and multiple sex chromosomes (male 2n = 36, Z1Z1Z2Z2/Z1Z2W, female 2n = 35, with variable W sex chromosome). Multiple sex chromosomes and their changes may influence meiosis and the female meiotic drive, and they may play a role in reproductive isolation. In two cryptic taxa of Z. vivipara with different W sex chromosomes, meiosis during early spermatogenesis and oogenesis proceeds normally, without any disturbances, with the formation of haploid spermatocytes, and in female meiosis with the formation of synaptonemal complexes (SCs) and the lampbrush chromosomes. In females, the SC number was constantly equal to 19 (according to the SC length, 16 SC autosomal bivalents plus three presumed SC sex chromosome elements). No variability in the chromosomes at the early stages of meiotic prophase I, and no significant disturbances in the chromosome segregation at the anaphase–telophase I stage, have been discovered, and haploid oocytes (n = 17) at the metaphase II stage have been revealed. There should be a factor/factors that maintain the multiple sex chromosomes, their equal transmission, and the course of meiosis in these cryptic forms of Z. vivipara.

In parthenogenetic hybrid Darevskia armeniaca species, the development of early oogenesis and early meiosis were analyzed. It has been shown for the first time that the number of synаptonemal complexes (SCs) of bivalents during the stages of early pachуtena–diplotena of the meiotic prophase 1 is constantly equal to the haploid number, 19. The SC karyotype is presented. The results of comparative molecular–cytogenetic (C/CMA 3 /DAPI) analysis of the mitotic chromosomes (2 n = 38: 34A + 2m + Zw-sex chromosomes) of parthenogenetic females and of the meiotic Zw - sex chromosomes ( n = 19 bivalents) of a male D. armeniaca specimen with sex inversion have been presented. Finally, the results obtained demonstrate the absence of premeiotic endoreplication of chromosomes, standard early stages of meiosis, and the formation of the haploid number of SC-bivalents ( n = 19) of homeological chromosomes in D. armeniaca .

Results of chromosomal and molecular studies of the lizard Zootoca vivipara (Lichtenstein, 1823) (Lacertidae) from many geographically separate populations of Europe and Asia have been generalized. The questions of ka­ryotype differences within the species, of diversity of its Zw and multiple Z1Z2W sex chromosome, their reorganizations and evolutionary consequences have been briefly considered. Stability of forming karyotypes is as an integrating factor which allow to identify the specimens and unite them into the groups possessing the distinct distribution areas. There are a correlation between chromosomal, mt DNA and nuclear DNA data. Finally all data obtained allow to draw a conclusion that Z. vivipara represents a cryptic group of cryptic taxa. Besides new data about the behavior of multiple sex chromosomes (SC, synaptonemal complexes) in early meiosis and molecular-cytogenetic data on transposable elements (TE) in the genome of Z. vivipara, their localization in the definite regions of chromosomes may suggest that they play a role in active speciation process by formation of cryptic taxa.

In the females of the viviparous lizard Zootoca vivipara (Lichtenstein, 1823) (family Lacertidae) from Northwest Russia (2n = 35: 32A (acrocentric autosomes) + Z(1)Z(2)W sex chromosomes), the ovarian lumen germinal vesicles (oocytes), as well as germinal lamina cells, were examined. Chromosome preparations were obtained using the direct method and the method of total oocyte nuclei spreading developed by Dresser and Moses. Chromosome preparations were stained with Giemsa; for visualization of synaptonemal complexes (SCs), total preparations of oocyte nuclei were stained with silver nitrate and DAPI. It was demonstrated that, during oogenesis in the female, primary follicles enter the early stages of the meiotic prophase I (stages from leptotene to diplotene, lampbrush chromosomes are formed). Here, for the first time, total oocyte spreads were obtained and studied. On the basis of light microscopic analysis of the oocyte SCs and taking into account their length in a female with 2n = 35, the SC karyotype is presented, consisting of 19 SC elements, among which 16 SC autosomal bivalents are distinguished. The remaining three SC elements, according to the authors, can be univalents of Z(1)Z(2)W sex chromosomes or one WZ(1) bivalent and Z(2) and Bchromosome univalents. As in the SC karyotype of Z. vivipara males, in a female, specific features in the morphology of SC elements of chromosomes 5 and 6 were observed.

The results of analysis of the frequencies of t -alleles and heterozygous +/ t individuals of house mice of different subspecies ( musculus, bactrianus, tataricus, wagneri , and gansuensis ) are presented for the natural populations inhabiting eight cities and five regions of Russia and adjacent countries of Eastern Europe and Asia. It is shown that the frequencies of t-alleles are 0.18 ± 0.03 in small samples (1–30 individuals) and 0.09 ± 0.06 in medium-sized samples (31–60 individuals). The factors that reduce the frequencies of t -alleles in natural populations and the mechanisms that prevent invasion and fixation of t -mutant alleles in the Mus musculus genome are discussed.

Somatic mitotic and meiotic chromosomes at the pachytene and at the metaphase I of the males of the viviparous lizard, Zootoca vivipara (Lichtenstein, 1823), from northwestern Russia, belonging to the Russian form of Z. v. vivipara, are examined. The spreading of synaptonemal complexes (SC) of their chromosomes are obtained and analyzed for the first time. Eighteen SC are observed, including SC of the Z1Z1 (pairs 5 or 6) and the Z2Z2 (pair 13) sex chromosomes. Characteristics of SC are compared with the number and the shape of bivalents and with those of the karyotype structure. In the studied Russian form of Z. v. vivipara, the length ratios of bivalents correlate with that of mitotic chromosomes (2n = 36); however, some specificity in the morphology of SC of the Z1Z1 sex chromosomes is reported in this article.

Meiotic drivers are genetic variants that selfishly manipulate the production of gametes to increase their own rate of transmission, often to the detriment of the rest of the genome and the individual that carries them. This genomic conflict potentially occurs whenever a diploid organism produces a haploid stage, and can have profound evolutionary impacts on gametogenesis, fertility, individual behaviour, mating system, population survival, and reproductive isolation. Multiple research teams are developing artificial drive systems for pest control, utilising the transmission advantage of drive to alter or exterminate target species. Here, we review current knowledge of how natural drive systems function, how drivers spread through natural populations, and the factors that limit their invasion.

The karyotype of males of two species of the genus Nothobranchius with the lowest diploid numbers was investigated: Nothobranchius rachovi (2N = 16) and Nothobranchius krysanovi (2N = 18). For the first time, whole mounts of spread syneptonemal complexes (SC) of these species were obtained and investigated. When the SC was painted with silver nitrate and immunostained with rabbit antibodies against the SCP3 protein, eight and nine homomorphic SCs were detected in the nuclei of class I spermatocytes of N. krysanovi and N. rachovi, respectively. The sex chromosomes were not identified.

The deviation of alleles and chromosomes from Mendelian inheritance is characteristic of the meiotic drive. This review describes the mechanism in question using the best-studied example of transmitted ratio distortion in the heterozygous male mice carrying t-haplotypes. The t-complex is best model for studying the meiotic drive under laboratory conditions. Putative mechanisms of meiotic drive that influence the frequency of t-haplotypes in natural populations are considered, of which prezygotic selection is the most important. The role of meiotic drive in male hybrid sterility is emphasized. The factors and models that determine the phenomenon of meiotic drive are discussed in detail.

Analysis of the B-chromosome frequency and morphotypes in 160 mice Apodemus peninsulae from 17 localities of the Baikal region, Northern Mongolia, Trans-Baikalia, and the Russian Far East showed that the mice were from five geographical populations. The interpopulation difference was determined by variations of 0–4 macro B chromosomes and 0–11 micro B chromosomes. The B-chromosome number and morphotypes proved to be stable over the past 30 years in the geographical populations under study.

We present an electronic microscopy (EM) analysis of synaptonemal complexes (SC) spermatocytes of male silver fox Vulpes fulvus at the pachytene stage. The SC-karyotypes of pachetene cells were made and described. Knowledge of normal SC-karyotype is necessary to reveal synaptic abnormalities of autosome and sex bivalents during the pachytene. It was indicated that EM analysis of SC-spermatocytes—the study of synaptonemal complexes in agricultural animals—is a very good instrument for comparative analysis of normal SC-karyotype of foxes that carry chromosomal abnormalities and in fur-bearing animals as well.

The results of light and electron microscopic (EM) studies of meiosis in Microtus arvalis males of the karyoform “arvalis” (2n = 46, NFa = 80), in hybrids between the chromosomal forms arvalis and obscurus (2n = 46, NFa = 68), in M. rossiaemeridionalis voles (2n = 54, NFa = 54), and in a hybrid between the species M. rossiaemeridionalis and kermanensis (2n = 54, NFa = 54) are presented. SC (synaptonemal complex) karyotypes of the parental forms and the hybrids were constructed on the basis of measurements of the length of autosomal SCs revealed by the EM analysis in spermatocytes at the stage of middle pachytene. The SC karyotypes of M. arvalis and the hybrids ♀ obscurus × ♂ arvalis consist of 22 synaptonemal complexes of autosomal bivalents and the axial elements of the synaptonemal complexes of the sex chromosomes X and Y. The SC karyotypes of M. rossiaemeridionalis and the hybrid M. rossiaemeridionalis × M. kermanensis consist of 26 synaptonemal complexes of autosomal bivalents and a sex bivalent; they differ only in the length of the Y chromosome axis (Y chromosome in the hybrid was inherited from M. kermanensis). Asynaptic configurations of the autosomal SCs were not observed in the hybrids. The SC axial elements of the X and Y chromosomes in the parental forms and in the hybrids were located close to each other throughout pachytene, but they did not form a synaptic region. The normal synapsis in sterile hybrids (M. rossiaemeridionalis × M. kermanensis) and the behavior of the sex chromosomes in meiosis in fertile and sterile hybrids are discussed in the context of specific features of meiosis and reproductive isolation.

Представлены результаты светового и электронно-микроскопического (ЭМ) анализа мейоза у самцов Microtus arvalis хромосомной формы “arvalis” (2n = 46, NFa = 80), гибридов между формами “arvalis” и “obscurus” (2n = 46, NFa = 68), M. rossiaemeridionalis (2n = 54, NFa = 54) и гибрида между видами M. rossiaemeridionalis и M. kermanensis (2n = 54, NFa = 54). На основе измерений длин синаптонемных комплексов (СК) аутосом, выявленных при ЭМ-анализе в сперматоцитах на стадии средней пахитены, составлены СК-кариотипы родительских форм и гибридов. СК-кариотипы M. arvalis и гибрида “obscurus” ? “arvalis” состоят из 22 СК аутосомных бивалентов и осевых элементов СК половых хромосом. СК-кариотипы M. rossiaemeridionalis и гибрида M. rossiaemeridionalis ? M. kermanensis состоят из 26 СК аутосомных бивалентов и полового бивалента; они различаются лишь по длине оси Y-хромосомы (у гибрида Y-хромосома унаследована от M. kermanensis). Асинаптических конфигураций СК аутосом у гибридов не наблюдалось. Осевые элементы СК X- и Y-хромосом у родительских форм и гибридов располагались близко друг к другу на протяжении всей пахитены, но не синаптировали. Нормальный синапсис у стерильных гибридов M. rossiaemeridionalis ? M. kermanensis и поведение половых хромосом в мейозе у фертильных и стерильных гибридов обсуждаются в контексте особенностей мейоза и репродуктивной изоляции.