Karyotype, C-band and NOR phenotype of Anatolian endemic fish Squalius anatolicus (Bogutskaya, 1997) (Teleostei, Leuciscidae)

The karyotype and distribution of constitutive heterochromatin and nucleolus organizer regions (NORs) of Anatolian leuciscine endemic to Lake Beysehir, Squalius anatolicus (Bogutskaya, 1997) were analyzed respectively using conventional Giemsa-staining, C-banding and Ag-impregnation. Diploid chromosome number was 2n = 50 and karyotype consisted of 7 pairs of metacentric, 13 pairs of submetacentric, 5 pairs of subtelo- to acrocentric chromosomes, NF value equaled 90. Heteromorphic elements indicating sex chromosomes were not detected. C-banding revealed clear pericentromeric constitutive heterochromatin blocks in several chromosomes. Ag-impregnation revealed the size heteromorphism of NORs that covered almost the entire short arms of the middle-sized submetacentric chromosome pair. The karyotype pattern and simple NOR phenotype of S. anatolicus are nearly identical with that found not only in Squalius species analyzed to date but also in many other representatives of the Eurasian leuciscine cyprinids, which indicates remarkable chromosome stasis in this leuciscid lineage.

Contributions to the taxonomy of Trachelyopterus (Siluriformes): comparative cytogenetic analysis in three species of Auchenipteridae

ABSTRACT Auchenipteridae is divided into subfamilies Centromochlinae and Auchenipterinae. Parauchenipterus is included in the latter and is subject of taxonomic discussions concerning its validation or synonymization with Trachelyopterus. Herein, three species from two hydrographic basins were cytogenetically analyzed: Parauchenipterus striatulus from Doce River and two sympatric species, P. galeatus and Trachelyopterus coriaceus, from the Araguaia River. Diploid number of 58 chromosomes was verified for all species, but P. striatulus has different karyotype formula from the others. The three species have heterochromatin located in terminal regions of almost all chromosomes and in pericentromeric region on acrocentric chromosomes. Simple NORs was verified on a subtelocentric chromosome for all species. 5S rDNA sites were detected in three submetacentric chromosome pairs in P. striatulus; in a metacentric chromosome pair and submetacentric pair in T. coriaceus; and in one metacentric chromosome pair in P. galeatus. The similarities found in the karyotypes of the three species suggest the existence of only one genus, Trachelyopterus; therefore, our data refutes the validation of Parauchenipterus. Moreover, the differences in 5S rDNA distribution in P. galeatus in comparison with other populations already studied, indicate the existence of a new taxonomic unit, which suggests a species complex in P. galeatus.

B Chromosomes and Cytogenetic Characteristics of the Common Nase Chondrostoma nasus (Linnaeus, 1758)

Supernumerary B chromosomes (Bs) are very promising structures, among others, in that they are an additional genomic compartment for evolution. In this study, we tested the presence and frequency of B chromosomes and performed the first cytogenetic examination of the common nase (Chondrostoma nasus). We investigated the individuals from two populations in the Vistula River basin, in Poland, according to the chromosomal distribution of the C-bands and silver nucleolar organizer regions (Ag-NORs), using sequential staining with AgNO3 and chromomycin A3 (CMA3). Furthermore, we analyzed the chromosomal localization of two rDNA families (45S and 5S rDNA) using fluorescence in situ hybridization (FISH) with rDNA probes. Chondrostoma nasus individuals showed a standard (A) chromosome set consisting of 2n = 50: 12 metacentric, 32 submetacentric, and 6 acrocentric chromosomes (NF = 94). Fourteen out of the 20 analyzed individuals showed 1–2 mitotically unstable submetacentric B chromosomes of different sizes. Six of them, in 14.1% of the analyzed metaphase plates, had a single, medium-sized submetacentric B (Bsm) chromosome (2n = 51) with a heterochromatic block located in its pericentromeric region. The other seven individuals possessed a Bsm (2n = 51) in 19.4% of the analyzed metaphase plates, and a second Bsm chromosome (2n = 52), the smallest in the set, in 15.5% of metaphase plates, whereas one female was characterized by both Bsm chromosomes (2n = 52) in 14.3% of the analyzed metaphase plates. AgNORs, GC-rich DNA sites, and 28S rDNA hybridization sites were observed in the short arms of two submetacentric chromosome pairs of A set. The constitutive heterochromatin was visible as C bands in the centromeric regions of almost all Chondrostoma nasus chromosomes and in the pericentromeric region of several chromosome pairs. Two 5S rDNA hybridization sites in the pericentromeric position of the largest acrocentric chromosome pair were observed, whereas two other such sites in co-localization on a smaller pair of NOR chromosomes indicate a species-specific character. The results herein broaden our knowledge in the field of B chromosome distribution and molecular cytogenetics of Chondrostoma nasus: a freshwater species from the Leuciscidae family.

Detecting Brachypodium distachyon Chromosomes Bd4 and Bd5 in MH- and X-Ray-Induced Micronuclei Using mcFISH

Micronuclei are biomarkers of genotoxic effects and chromosomal instability. They are formed when chromosome fragments or whole chromosomes fail to disjoin into daughter nuclei. We present qualitative and quantitative analyses of the involvement of specific chromosome regions of chromosomes Bd4 and Bd5 in the formation of micronuclei of Brachypodium distachyon root tip cells following maleic hydrazide (MH) treatment and X-radiation. This is visualised by cytomolecular approaches using bacterial artificial chromosome (BAC)-based multicolour fluorescence in situ hybridisation (mcFISH) in combination with 5S and 25S rDNA probes. The results showed that the long arm of submetacentric chromosome Bd4 forms micronuclei at twice the frequency of its short arm, suggesting that the former is more prone to double-strand breaks (DSBs). In contrast, no difference was observed in the frequency of micronuclei derived from the long and short arms of submetacentric chromosome Bd5. Interestingly, the proximal region of the short arm of Bd5 is more prone to DSBs than its distal part. This demonstrates that 5S rDNA and 35S rDNA loci are not “hot spots” for DNA breaks after the application of these mutagens.

First chromosomal analysis of Gymnorhamphichthys britskii: the remarkable lowest diploid value within the family Rhamphichthyidae (Gymnotiformes)

ABSTRACT Gymnorhamphichthys britskii is a Neotropical electric fish of family Rhamphichthyidae described from the Paraná-Paraguay system. This study reports the first karyotypic description of G. britskii collected from the upper Paraná river basin, which presented 2n=38 chromosomes, karyotype composed of 14 metacentric, 8 submetacentric, 2 subtelocentric and 14 acrocentric chromosomes, and fundamental number as 62 for both sexes. Heteromorphic sex chromosomes were absent. A single pair of nucleolar organizing regions (NORs) was detected in the submetacentric chromosome pair number 9 by silver staining and confirmed by the 18S rDNA probe. The 5S rDNA was located in a single chromosome pair. Heterochromatic regions were clearly observed in the short arms of the NOR-bearing chromosome pair and in the telomeric positions of most acrocentric chromosomes. Besides the present data are valuable to help in understanding karyotypic evolution in Rhamphichthyidae, data from NORs confirmed the tendency of this family in presenting simple NORs sites, similar to the other Gymnotiformes clades. Yet, the presence of a large heterochromatic block in the NOR-bearing chromosome can be used as cytogenetic markers for G. britskii, and that centric fusions appear to be an important mechanism in the karyotype evolution and differentiation among Gymnotiformes species.

Karyotype and chromosomal characteristics of rDNA of Cobitis strumicae Karaman, 1955 (Teleostei, Cobitidae) from Lake Volvi, Greece

The karyotype of Greek cobitid fish Cobitisstrumicae Karaman, 1955, from Lake Volvi, Greece, a representative of one of its two major intraspecific phylogenetic lineages, was analysed by means of sequential Giemsa-staining, C-banding, silver-staining, CMA3 fluorescence banding and also by in situ hybridization (FISH) with rDNA probe. The diploid chromosome number was 2n = 50, karyotype composed of 10 pairs of metacentric to submetacentric and 15 pairs of subtelocentric to acrocentric chromosomes. The nucleolus organizer regions (NORs) as revealed by Ag- and CMA3 staining and FISH were situated in the telomeric region of the fourth submetacentric chromosome pair. The chromosomes contained very low content of C-positive heterochromatin. No heteromorphic sex chromosomes were detected. This first karyotype report for any species of lineage Bicanestrinia Băcescu, 1962 shows a simple karyotype dominated by acrocentric chromosomes and possessing single NOR-bearing chromosome pair. Cytotaxonomic implications of this finding for the taxonomy of the genus Cobitis Linnaeus, 1758 are further discussed.

Karyotype Characterization of Nine Periwinkle Species (Gastropoda, Littorinidae)

Periwinkles of the family Littorinidae (Children, 1834) are common members of seashore littoral communities worldwide. Although the family is composed of more than 200 species belonging to 18 genera, chromosome numbers have been described in only eleven of them. A molecular cytogenetic analysis of nine periwinkle species, the rough periwinkles Littorina arcana, L. saxatilis, and L. compressa, the flat periwinkles L. obtusata and L. fabalis, the common periwinkle L. littorea, the mangrove periwinkle Littoraria angulifera, the beaded periwinkle Cenchritis muricatus, and the small periwinkle Melarhaphe neritoides was performed. All species showed diploid chromosome numbers of 2n = 34, and karyotypes were mostly composed of metacentric and submetacentric chromosome pairs. None of the periwinkle species showed chromosomal differences between male and female specimens. The chromosomal mapping of major and minor rDNA and H3 histone gene clusters by fluorescent in situ hybridization demonstrated that the patterns of distribution of these DNA sequences were conserved among closely related species and differed among less related ones. All signals occupied separated loci on different chromosome pairs without any evidence of co-localization in any of the species.

Centromere Fissions, Complementary Isochromosomes, Telomeric Fusions, Balancing Supernumerary Chromosomes, Neocentromeres, Jumping Translocations, and Chromothripsis

This chapter reviews a number of very rare chromosomal rearrangements: centromere fissions, complementary isochromosomes, telomeric fusions, balancing supernumerary chromosomes, neocentromeres, jumping translocations, and chromothripsis. Centromere fission results when a metacentric or submetacentric chromosome splits at the centromere, giving rise to two stable telocentric products. The Robertsonian fission reverses the fusion that had originally generated it. Telomeric fusion leads to a 45-chromosome count. With the balanced complementary isochromosome carrier, two stable exactly metacentric products are generated. A balancing small supernumerary marker chromosome contains material deleted from the normal homolog. A supernumerary chromosome lacking a normal centromere can become stable and functional due to the generation of a neocentromere. In jumping translocations, a segment can move from one chromosome to two or more recipient chromosomes. Chromothripsis takes complex rearrangement to a yet more complex level. The reproductive risks associated with each are noted.

Chromosome Banding in Amphibia. XXXVI. Multimorphic Sex Chromosomes and an Enigmatic Sex Determination in Eleutherodactylus johnstonei (Anura, Eleutherodactylidae)

A detailed cytogenetic study on the leaf litter frog Eleutherodactylus johnstonei from 14 different Caribbean islands and the mainlands of Venezuela and Guyana revealed the existence of multimorphic XY♂/XX♀ sex chromosomes 14. Their male sex determination and development depends either on the presence of 2 telocentric chromosomes 14 (XtYt), or on 1 submetacentric chromosome 14 (Xsm) plus 1 telocentric chromosome 14 (Yt), or on the presence of 2 submetacentric chromosomes 14 (XsmYsm). The female sex determination and development requires either the presence of 2 telocentric chromosomes 14 (XtXt) or 2 submetacentric chromosomes 14 (XsmXsm). In all individuals analyzed, the sex chromosomes 14 carry a prominent nucleolus organizer region in their long arms. An explanation is given for the origin of the (XtYt)♂, (XsmYt)♂, (XsmYsm)♂, (XtXt)♀, and (XsmXsm)♀ in the different populations of E. johnstonei. Furthermore, the present study gives detailed data on the chromosome banding patterns, in situ hybridization experiments, and the genome size of E. johnstonei.

Morphology, anatomy and karyology of endangered Turkish endemic Physoptychis haussknechtii Bornm. (Brassicaceae) from Central Anatolia

In this study, the morphology, anatomy, pollen morphology, leaf and seed micromorphology and karyology of the Turkish endangered endemic Physoptychis haussknechtii were investigated in detail for the first time. The species was studied in terms of detailed morphology. Basal leaves are narrowly spatulate and cauline leaves are linear to oblanceolate; both leaves are covered with flattened stalked five-armed trichomes. Raceme length was found to be up to 6 cm and 9 cm in the flowering and fruiting stages, respectively. Sepals are linear-oblong, rarely elliptic with obtuse to subacute apex. Petals are spatulate with emarginate apex. Some morphological characteristics such as dimensions of cauline leaves and ovary and length of pistil were measured for the first time. In an anatomical study, root, stem, basal leaf and cauline leaf were examined. The anatomical results showed that the plants have secondary growth in roots, primary growth in stems, amphistomatic and equifacial basal and cauline leaves with anisocytic stomata. Pollen grains are radial symmetrical, isopolar and tricolpate. The ratio of polar axis to equatorial diameter is 1.16, and pollen shape is subprolate. Exine sculpturing is reticulate under light microscope and scanning electron microscope. Seeds are obovatesuborbicular, compressed and pale brown. The chromosome number of P. haussknechtii was defined to be 2n=16. The karyotype formula of P. haussknechtii consists of five metacentric chromosome pairs and three submetacentric chromosome pairs.