Comparative Cytogenetics最新文献

The African family Distichodontidae comprises 109 species in 16 genera. Up-to-date cytogenetic information was available for the only distichodontid species Distichodusaffinis Günther, 1873. Here we report chromosome number and morphology in: Distichodusengycephalus Günther, 1864 (2n = 52, FN = 104), Ichthyborusbesse (Joannis, 1835) (2n = 46, FN = 92), Nannocharaxniloticus (Joannis, 1835) (2n = 54, FN = 106) and three taxa, Nannaethiopsbleheri Géry et Zarske, 2003, Nannaethiops sp., and Neolebiasunifasciatus Steindachner, 1894, that exhibit the same karyotypes (2n = 50, FN = 98). To confirm the Nannaethiops Günther, 1872 and Neolebias Steindachner, 1894 species identification, mt-DNA sequences of the two markers (COI and 16S rRNA) were obtained from karyotyped specimens and compared with the relevant sequences accessible from GenBank. The great prevalence of biarmed chromosomes (the karyotypes of most species contain exclusively biarmed chromosomes) is a distinctive characteristic of Distichodontidae and Cithariniformes as a whole.

A brief overview of the current stage of the chromosome study of the insect order Hymenoptera is given. It is demonstrated that, in addition to routine staining and other traditional techniques of chromosome research, karyotypes of an increasing number of hymenopterans are being studied using molecular methods, e.g., staining with base-specific fluorochromes and fluorescence in situ hybridization (FISH), including microdissection and chromosome painting. Due to the advent of whole genome sequencing and other molecular techniques, together with the "big data" approach to the chromosomal data, the current stage of the chromosome research on Hymenoptera represents a transition from Hymenoptera cytogenetics to cytogenomics.

It is demonstrated that the initial method of fertilization in animals (Metazoa), embryophyte plants (Embryophyta), most groups of multicellular oogamous algae, oogamous and pseudoogamous multicellular fungi was internal fertilization (in the broad meaning) in/on the body of a maternal organism. Accordingly, during the bisexual process, the initial method of formation of a daughter multicellular organism in animals was viviparity, and in embryophyte plants and most groups of oogamous multicellular algae - the germination of a zygote in/on the body of maternal organism. The reproductive criteria of multicellularity are proposed and discussed. In this regard, the multicellularity is considered to subdivide terminologically into three variants: 1) protonemal, the most simple, characteristic of multicellular prokaryotes, most groups of multicellular algae and gametophytes of some higher plants; 2) siphonoseptal, found among multicellular fungi, some groups of green and yellow-green algae; 3) embryogenic, most complicated, known in all animals (Metazoa), all sporophytes and some gametophytes of higher plants (Embryophyta), charophyte green algae Charophyceae s.s., oogamous species of green and brown algae, some genera of red algae. In addition to the well-known division of reproduction methods into sexual and asexual, it is proposed to divide the reproduction of multicellular organisms into monocytic (the emergence of a new organism from one cell sexually or asexually) and polycytic (fragmentation, longitudinal / transverse division or budding based on many cells of the body of the mother organism), since these two ways have different evolutionary and ontogenetic origins.

Cyprininae are a highly diversified but demonstrably monophyletic lineage of cypriniform fishes. Here, the karyotype and chromosomal characteristics of Hypsibarbusmalcolmi (Smith, 1945) and H.wetmorei (Smith, 1931) were examined using conventional, nucleolus organizing regions (NORs) and molecular cytogenetic protocols. The diploid chromosome number (2n) of H.malcolmi was 50, the fundamental number (FN) was equal to 62, and the karyotype displayed 8m + 4sm + 38a with NORs located at the centromeric and telomeric positions of the short arms of chromosome pairs 1 and 2, respectively. 2n of H.wetmorei was 50, FN 78, karyotype 14m + 14sm + 22a with the NORs at the telomeric position of the short arm of chromosome pair 2. 2n and FN in males and females were identical. Fluorescence in situ hybridization using different microsatellite motifs as probes also showed substantial genomic divergence between both studied species. In H.wetmorei, (CAG)_n and (CAC)_n microsatellites accumulated in the telomeric regions of all chromosomes, while in H.malcolmi, they had scattered signals on all chromosomes. Besides, the (GAA)n microsatellites were distributed along all chromosomes of H.malcolmi, but there was a strong hybridization pattern in the centromeric region of a single pair in H.wetmorei. These cytogenomic difference across the genomes of these Hypsibarbus Rainboth, 1996 species are markers for specific evolutionary differentiation within these two species.

The family Formicidae is composed of ants that organize themselves into castes in which every individual has a joint organizational function. Solenopsis Westwood, 1840 is an ant genus with opportunistic and aggressive characteristics, known for being invasive species and stings that cause burning in humans. This genus is particularly difficult to classify and identify since its morphology provides few indications for species differentiation. For this, a tool that has been useful for evolutionary and taxonomic studies is cytogenetics. Here, we cytogenetically studied Solenopsissaevissima Smith, 1855 from Ouro Preto, Minas Gerais, Brazil. We evaluated the occurrence of polyploid cells in individuals and colonies by conventional cytogenetics. A total of 450 metaphases were analyzed and counted. Chromosome counts of individuals and colonies showed varied numbers of ploidies, from n = 16 to 8n = 128. The karyomorphometrical approach allowed determination of the following karyotypes: n = 10 m + 4 sm + 2 st, 2n = 20 m + 8 sm + 4 st, and 4n = 40 m + 16 sm + 8 st. Polyploidy can be found naturally in individuals and colonies and may represent an adaptative trait related to widespread distribution and invasion ability of new habitats.

To have an insight into the karyotype variation of eight Cucurbitaceae crops including Cucumissativus Linnaeus, 1753, Cucumismelo Linnaeus, 1753, Citrulluslanatus (Thunberg, 1794) Matsumura et Nakai, 1916, Benincasahispida (Thunberg, 1784) Cogniaux, 1881, Momordicacharantia Linnaeus, 1753, Luffacylindrica (Linnaeus, 1753) Roemer, 1846, Lagenariasicerariavar.hispida (Thunberg, 1783) Hara, 1948 and Cucurbitamoschata Duchesne ex Poiret, 1819, well morphologically differentiated mitotic metaphase chromosomes were prepared using the enzymatic maceration and flame-drying method, and the chromosomal distribution of heterochromatin and 18S-5.8S-26S rRNA genes (45S rDNA) was investigated using sequential combined PI and DAPI (CPD) staining and fluorescence in situ hybridization (FISH) with 45S rDNA probe. Detailed karyotypes were established using the dataset of chromosome measurements, fluorochrome bands and rDNA FISH signals. Four karyotype asymmetry indices, CV_CI, CV_CL, M_CA and Stebbins' category, were measured to elucidate the karyological relationships among species. All the species studied had symmetrical karyotypes composed of metacentric and submetacentric or only metacentric chromosomes, but their karyotype structure can be discriminated by the scatter plot of M_CA vs. CV_CL. The karyological relationships among these species revealed by PCoA based on x, 2n, TCL, M_CA, CV_CL and CV_CI was basically in agreement with the phylogenetic relationships revealed by DNA sequences. CPD staining revealed all 45S rDNA sites in all species, (peri)centromeric GC-rich heterochromatin in C.sativus, C.melo, C.lanatus, M.charantia and L.cylindrica, terminal GC-rich heterochromatin in C.sativus. DAPI counterstaining after FISH revealed pericentromeric DAPI⁺ heterochromatin in C.moschata. rDNA FISH detected two 45S loci in five species and five 45S loci in three species. Among these 45S loci, most were located at the terminals of chromosome arms, and a few in the proximal regions. In C.sativus, individual chromosomes can be precisely distinguished by the CPD band and 45S rDNA signal patterns, providing an easy method for chromosome identification of cucumber. The genome differentiation among these species was discussed in terms of genome size, heterochromatin, 45S rDNA site, and karyotype asymmetry based on the data of this study and previous reports.

The karyotype differentiation of the twelve known members of the Nothobranchiusugandensis Wildekamp, 1994 species group is reviewed and the karyotype composition of seven of its species is described herein for the first time using a conventional cytogenetic protocol. Changes in the architecture of eukaryotic genomes often have a major impact on processes underlying reproductive isolation, adaptation and diversification. African annual killifishes of the genus Nothobranchius Peters, 1868 (Teleostei: Nothobranchiidae), which are adapted to an extreme environment of ephemeral wetland pools in African savannahs, feature extensive karyotype evolution in small, isolated populations and thus are suitable models for studying the interplay between karyotype change and species evolution. The present investigation reveals a highly conserved diploid chromosome number (2n = 36) but a variable number of chromosomal arms (46-64) among members of the N.ugandensis species group, implying a significant role of pericentric inversions and/or other types of centromeric shift in the karyotype evolution of the group. When superimposed onto a phylogenetic tree based on molecular analyses of two mitochondrial genes the cytogenetic characteristics did not show any correlation with the phylogenetic relationships within the lineage. While karyotypes of many other Nothobranchius spp. studied to date diversified mainly via chromosome fusions and fissions, the N.ugandensis species group maintains stable 2n and the karyotype differentiation seems to be constrained to intrachromosomal rearrangements. Possible reasons for this difference in the trajectory of karyotype differentiation are discussed. While genetic drift seems to be a major factor in the fixation of chromosome rearrangements in Nothobranchius, future studies are needed to assess the impact of predicted multiple inversions on the genome evolution and species diversification within the N.ugandensis species group.

Snakehead fishes of the family Channidae are obligatory air-breathers freshwater predators, the vast majority of which belong to the genus Channa Scopoli, 1777. Channa species are characterized by high karyotypic diversity due to various types of chromosomal rearrangements. It is assumed that, in addition to the lifestyle, fragmentation and isolation of snakehead populations contribute to an increase in karyotypic diversity. However, the chromosome complements of many isolated populations of widespread Channa species remain unknown, and the direction of karyotype transformations is poorly understood. This paper describes the previously unstudied karyotypes of Channalucius (Cuvier, 1831) and C.striata (Bloch, 1793) from Phu Quoc Island and analyzes the trends of karyotypic evolution in the genus Channa. In C.lucius, the karyotypes are differed in the number of chromosome arms (2n = 48, NF = 50 and 51), while in C.striata, the karyotypes are differed in the diploid chromosome number (2n = 44 and 43, NF = 48). A comparative cytogenetic analysis showed that the main trend of karyotypic evolution of Channa species is associated with a decrease in the number of chromosomes and an increase in the number of chromosome arms, mainly due to fusions and pericentric inversions. The data obtained support the assumption that fragmentation and isolation of populations, especially of continental islands, contribute to the karyotypic diversification of snakeheads and are of interest for further cytogenetic studies of Channidae.

The karyotype of the freshwater fish Sabanejewiabulgarica (Drensky, 1928), from the Danube Delta, was studied by conventional Giemsa staining and the C-banding technique. The diploid chromosome number was 2n = 50. The karyotype contained 2 pairs of metacentric (the first one was much larger than the second one), 6 pairs of submetacentric and 17 pairs of subtelocentric to acrocentric chromosomes. Pericentromeric blocks of heterochromatin were revealed in most of the chromosome pairs. The karyotype phenotype of S.bulgarica was the same as found for S.balcanica from Northern Carpathian Mountains.