Cytogenetic characterization of <Emphasis Type="Italic">Lippia alba</Emphasis> and <Emphasis Type="Italic">Lantana camara</Emphasis> (Verbenaceae) from Brazil

The aim of this work was to determine the cytogenetic characteristics of Brazilian Lippia alba (Mill) N. E. Brown and Lantana camara Plum. that could be useful for future characterization of these genera. Our analyses revealed that Li. alba has 2n=30 chromosomes consisting of ten metacentric and five submetacentric pairs, while La. camara has 44 metacentric chromosomes. The large blocks of heterochromatin seen in both species suggest an apomorphic condition. Six 45S rDNA sites were detected in both species by fluorescence in situ hybridization (FISH). Two and four 5S rDNA sites were observed in Li. alba and La. camara, respectively. Meiotic analysis revealed a normal chromosomal behaviour. The number of chromosomes and the presence of 45S rDNA and 5S rDNA sites do not exclude a possible polyploid origin. The cytogenetic differences between La. camara and Li. alba may be useful markers for differentiating these species.     

Occurrence of two cytotypes in <Emphasis Type="Italic">Bryconamericus</Emphasis> aff. <Emphasis Type="Italic">iheringii</Emphasis> (Characidae): karyotype analysis by C- and G-banding and replication bands

Cytogenetic analyses of Bryconamericus aff. iheringii specimens from the upper Paraná River basin (State of Paraná, Brazil) are provided. They had 2n = 52 chromosomes and two cytotypes with variations in their karyotypic formulae: cytotype I with 12 metacentric, 18 submetacentric, 8 subtelocentric and 14 acrocentric chromosomes with a fundamental number (FN) of 90; cytotype II with 8 metacentric, 28 submetacentric, 6 subtelocentric and 10 acrocentric chromosomes with a fundamental number (FN) of 94. Differences in C- and G-band patterns between the cytotypes, distinguishing marker chromosomes for each karyotype, were reported. The R-band pattern by 5-bromodeoxyuridine incorporation was obtained in chromosomes of the cytotype II sample. In some metaphases, the second pair of submetacentric chromosomes is distinctive: its short arm is heterochromatic (positive C-band), corresponding to a late replication region. In the same cytotype, a G- and R-band size heteromorphism w as recorded in the long arm of pair 9 (submetacentric). These methodologies revealed an actual karyotypic differentiation in the B. aff. iheringii population analyzed. Morphometrical comparative analyses and a discussion of evolutionary aspects of chromosome diversification in species of this genus are provided as well.     

Karyotype study in <Emphasis Type="Italic">Luzuriaga radicans</Emphasis> (Liliales: Luzuriagaceae)

The karyotype of Luzuriaga radicans R. & P. was quantitatively studied, assessing characters such as chromosome morphology and size, satellite location, asymmetry level and bimodality. L. radicans has an asymmetric and bimodal karyotype 2n = 20 with three metacentric pairs, followed by six submetacentric and one subtelocentric chromosome pair. One satellite was observed in the short arm of chromosome pair 6. The total haploid set length was 48.7 μm and the mean chromosome size was 4.87 ± 2.35 μm. Comparing L. radicans with other two species of the genus a high resemblance among their karyotypes was found.     

Identification of parental genomes and genomic organization in <Emphasis Type="Italic">Aster microcephalus</Emphasis> var. <Emphasis Type="Italic">ovatus</Emphasis>

The karyotype of diploid Aster iinumae is morphologically similar to that of diploid Aster ageratoides var. ageratoides, however, its chromosome size is apparently smaller (S-type chromosomes versus L-type chromosomes, respectively). The hybrid origin of tetraploid Aster microcephalus var. ovatus (LS-type chromosomes) has previously been suggested by cytogenetics and chloroplast DNA (cp DNA) data. The cp DNA phylogeny also implies that the S-type chromosome is apomorphic, which means that genome size reduction occurred on the evolutionary way to A. iinumae. In this study, we have demonstrated that the chromosome size difference does not depend on the intensity of chromosome condensation but on the DNA content. The simultaneous genomic in situ hybridization (GISH) results show the similarity between S-type chromosomes of A. iinumae and A. microcephalus var. ovatus, and between L-type chromosomes of A. ageratoides and A. microcephalus var. ovatus, which provide additional evidence for A. microcephalus var. ovatus being a tetraploid amphidiploid produced by hybridization between S-type chromosomes and L-type chromosomes. The distribution patterns of Ty1-copia-like retrotransposons were similar in L- and S-type chromosomes. The copies of this retrotransposon dispersed uniformly on all chromosomes, and it is not yet apparent how the Ty1-copia-like retrotransposon affects the size difference between them.     

Karyotype analysis and new chromosome number reports in <Emphasis Type="Italic">Silene</Emphasis> species (sect. <Emphasis Type="Italic">Auriculatae</Emphasis>, Caryophyllaceae)

Karyotype study was performed in 13 populations of 11 Silene species (sect. Auriculatae L., Caryophyllaceae) growing in Iran. All the species studied showed 2n = 2x = 24 chromosome number supporting the earlier report on S. meyeri, while the chromosome number of S. palinotricha, S. sojakii, S. gertraudiae, S. elymaitica, S. pseudonurensis, S. dschuparensis, S. eriocalycina, S. araratica, S. prilipkoana and S. commelinifolia are new to science. The chromosomes were mainly metacentric or sub-metacentric and their size varied from 1.10 μm in S. pseudonurensis to 7.11 μm in S. dschuparensis. The species studied differed significantly in the total size of the chromosomes, the size of the short arms and the long arms, indicating the role of quantitative genomic changes in the Silene species diversification. They also differ in their karyotype formulae indicating the occurrence of structural changes in their chromosomes. The Silene species were placed in 1A, 2A, 1B and 2B classes of Stebbins karyotype symmetry showing symmetrical karyotypes. Clustering of the species based on karyotype features grouped the species of S. palinotricha, S. prilipkoana, S. commelinifolia, S. eriocalycina, S. meyeri, S. araratica and S. Sojakii together while the species of S. gertraudiae and S. elymaitica showed more similarity and were placed close to each other.     

Chromosome banding and essential oils composition of Brazilian accessions of <Emphasis Type="Italic">Lippia alba</Emphasis> (Verbenaceae)

The essential oil components and a karyotypic analysis of five Lippia alba (Verbenaceae) accessions from Brazil were performed with the objective of investigating the variation among different populations. The chemistry analysis allowed the grouping of the accessions in two main chemotypes: neral chemotype (LaCat, LaJF and LaRJ) and linalool chemotype (LaGua and LaVC). However, large karyotypic differences, verified by different chromosome banding techniques, were not detected. The results presented the same chromosome number for all accessions (2n = 30) with 10 metacentric chromosomes and 5 submetacentric. The chromosome banding showed great blocks of constitutive heterochromatin (C-bands) around the centromeric region, which was rich in AT bases (DAPI₊), while the CMA bands were observed only in terminal regions of six chromosomes. Through Ag-NOR techniques, only two active pairs of NORs were detected on the three pairs of secondary constrictions (the NOR activity is discussed). This work relates the pattern of heterochromatin for Lippia alba for the first time.     

Comparison of genomes of eight species of sections <Emphasis Type="Italic">Linum</Emphasis> and <Emphasis Type="Italic">Adenolinum</Emphasis> from the genus<Emphasis Type="Italic"> Linum</Emphasis> based on chromosome banding,molecular markers and RAPD analysis

Karyotypes of species sects. Linum and Adenolinum have been studied using C/DAPI-banding, Ag-NOR staining, FISH with 5S and 26S rDNA and RAPD analysis. C/DAPI-banding patterns enabled identification of all homologous chromosome pairs in the studied karyotypes. The revealed high similarity between species L. grandiflorum (2n = 16) and L. decumbens by chromosome and molecular markers proved their close genome relationship and identified the chromosome number in L. decumbens as 2n = 16. The similarity found for C/DAPI-banding patterns between species with the same chromosome numbers corresponds with the results obtained by RAPD-analysis, showing clusterization of 16-, 18- and 30-chromosome species into three separate groups. 5S rDNA and 26S rDNA were co-localized in NOR-chromosome 1 in the genomes of all species investigated. In 30-chromosome species, there were three separate 5S rDNA sites in chromosomes 3, 8 and 13. In 16-chromosome species, a separate 5S rDNA site was also located in chromosome 3, whereas in 18-chromosome species it was found in the long arm of NOR-chromosome 1. Thus, the difference in localization of rDNA sites in species with 2n = 16, 2n = 30 and 2n = 18 confirms taxonomists opinion, who attributed these species to different sects. Linum and Adenolinum, respectively. The obtained results suggest that species with 2n = 16, 2n = 18 and 2n = 30 originated from a 16-chromosome ancestor.     

Karyological studies on eight species of <Emphasis Type="Italic">Onobrychis</Emphasis> genus in Turkey

This study used karyological techniques to determine the chromosome numbers and morphology of eight species of Onobrychis L. (O. caput-galli (L.) Lam, O. aequidentata (Sibth. & Sm.) d’ Urv, O. fallax Freyn & Sint. var. fallax, O. lasiostachya Boiss, O. viciifolia Scop., O. oxyodonta Boiss. subsp. armena (Bois. & Huet) Aktoklu, O. hypargyrea Boiss. and O. cappadocica Boiss.). The results of this study determined the chromosome numbers of O. cappadocica as 2n = 16; O. viciifolia as 2n = 28 and the other species as 2n = 14 The karyotypes of species consisted of median-centromeric (m) or submedian-centromeric (sm) chromosomes. However, O. oxyodonta Boiss. subsp. armena (Bois. & Huet) Aktoklu was found to have only the median-centromeric (m) chromosomes. According to the results of the present study, of the eight Onobrychis taxa, only O. hypargyrea has a pair of satellite chromosomes (sat-chromosome). Furthermore, this study detected karyotype asymmetry.     

Karyotypes of metaphase chromosomes in diploid populations of<Emphasis Type="Italic"> Dendranthema zawadskii</Emphasis> and related species (Asteraceae) from Korea: diversity and evolutionary implications

Although the Dendranthema zawadskii complex has been known to comprise a series of polyploids (4×, 6×, 8×), we found diploid individuals (with 2n=18) to occur in four populations of D. zawadskii var. latilobum in the southern region of Korea. Karyotypes of metaphase chromosomes were diverse because numbers of metacentric, submetacentric, and acrocentric chromosomes differ even within a population. A total of 17 karyotypes were found in 31 diploid individuals collected from the four populations. The karyotypes were also diverse in the presence or absence of chromosomes with a secondary constriction on a short or long arm and, if present, in the number of such chromosomes. They were further diverse in the presence or absence of non-homologous chromosome(s), the presence or absence of a chromosome with a satellite, and, if present, how many and where satellites are present. Almost the same pattern of diversity was found in diploid individuals (with 2n=18) of D. boreale and D. indicum as well, irrespective of whether they occur together with D. zawadskii var. latilobum or not. Structural features of chromosomes in the variously different karyotypes suggest that reciprocal translocation and the hybridization between individuals with different karyotypes had repeatedly occurred not only in D. zawadskii var. latilobum, but also in D. boreale and D. indicum. Morphologically intermediate individuals between D. zawadskii var. latilobum and D. indicum suggests that the hybridization occur with different species as well. Electronic Publication     

A high-resolution karyotype of <Emphasis Type="Italic">Brassica rapa</Emphasis> ssp. <Emphasis Type="Italic">pekinensis</Emphasis> revealed by pachytene analysis and multicolor fluorescence in situ hybridization

A molecular cytogenetic map of Chinese cabbage (Brassica rapa ssp. pekinensis, 2n=20) was constructed based on the 4-6-diamino-2-phenylindole dihydrochloride-stained mitotic metaphase and pachytene chromosomes and multicolor fluorescence in situ hybridization (McFISH), using three repetitive DNA sequences, 5S rDNA, 45S rDNA, and C11-350H. The lengths of mitotic metaphase chromosomes ranged from 1.46 m to 3.30 m. Five 45S and three 5S rDNA loci identified were assigned to different chromosomes. The C11-350H loci were located on all the mitotic metaphase chromosomes, except chromosomes 2 and 4. The pachytene karyotype consisted of two metacentric (chromosomes 1 and 6), five submetacentric (chromosomes 3, 4, 5, 9 and 10), two subtelocentric (chromosomes 7 and 8), and one acrocentric (chromosome 2) chromosome(s). The mean lengths of ten pachytene chromosomes ranged from 23.7 m to 51.3 m, with a total of 385.3 m, which is 17.5-fold longer than that of the mitotic metaphase chromosomes. In the proposed pachytene karyotype, all the chromosomes of B. rapa ssp. pekinensis can be identified on the basis of chromosome length, centromere position, heterochromatin pattern, and the location of the three repetitive sequences. Moreover, the precise locations of the earlier reported loci of 5S rDNA, 45S rDNA, and Chinese cabbage tandem DNA repeat C11-350H were established using McFISH analysis. We also identified a 5S rDNA locus on the long arm of pachytene bivalent 7, which could not be detected in the mitotic metaphase chromosomes in the present and earlier studies. The deduced karyotype will be useful for structural and functional genomic studies in B. rapa.     

The karyology of the cyprinid genera <Emphasis Type="Italic">Scardinius</Emphasis> and <Emphasis Type="Italic">Rutilus</Emphasis> in southern Europe

The chromosomes of eight species of Rutilus and Scardinius, mostly endemic to the Italian and the Balkan peninsula, were analyzed by conventional and other banding techniques. Parallel analyses were conducted also on two leuciscine species, Alburnus albidus, for which we provide the first karyological analysis, and Leuciscus cephalus. All species examined displayed the same karyotype (2n=50 chromosomes, 8 metacentric+13 submetacentric+4 subtelo/acrocentric pairs) with nucleolus organizer regions (NORs) on the ends of the shorter arms of a medium-sized submetacentric pair. In contrast, interspecific variation was observed in the distribution of constitutive heterochromatin. The variation observed in this genomic material proved to be systematically and phylogenetically informative. Indeed, a peritelomeric C-band on the first telocentric pair characterizes species of Rutilus and Scardinius. In both genera heterochromatin differentiation appears to be directed to a centromere–telomere direction, particularly evident along the metacentric elements of their karyotypes.An erratum to this article can be found at     

Comparative Molecular Cytogenetic Analysis of Two Congeneric Species, <Emphasis Type="Italic">Mugil Curema</Emphasis> and <Emphasis Type="Italic">M. Liza</Emphasis> (Pisces,Mugiliformes), Characterized by Significant Karyotype Diversity

Two congeneric mullet species, Mugil liza and M. curema, respectively with an all-uniarmed and an all-biarmed karyotype, were cytogenetically studied by base-specific fluorochrome staining and FISH-mapping of 45S and 5S ribosomal RNA genes (rDNA) and the (TTAGGG)_n telomeric repeats. Whereas 45S rDNA sites might be homeologus in the two species, 5S rDNA sites are not, as they are localized on chromosome arms of different size. In both species, the (TTAGGG)_n telomeric probe hybridized to natural telomeres and was found scattered along the NORs. In metacentric chromosomes of M. curema, no pericentromeric signals of the telomeric probe were detected. Data are discussed in relation to the karyotype evolution in Mugilidae and to the mechanisms and the evolutionary implications of Robertsonian rearrangements in M. curema.     

Cytogenetic characterization and mapping of rDNAs,core histone genes and telomeric sequences in <Emphasis Type="Italic">Venerupis aurea</Emphasis> and <Emphasis Type="Italic">Tapes rhomboides</Emphasis> (Bivalvia: Veneridae)

We describe the chromosomal location of GC-rich regions, 28S and 5S rDNA, core histone genes, and telomeric sequences in the veneroid bivalve species Venerupis aurea and Tapes (Venerupis) rhomboides, using fluorochrome staining with propidium iodide, DAPI and chromomycin A3 (CMA) and fluorescent in situ hybridization (FISH). DAPI dull/CMA bright bands were coincident with the chromosomal location of 28S rDNA in both species. The major rDNA was interstitially clustered at a single locus on the short arms of the metacentric chromosome pair 5 in V. aurea, whereas in T. rhomboides it was subtelomerically clustered on the long arms of the subtelocentric chromosome pair 17. 5S rDNA also was a single subtelomeric cluster on the long arms of subtelocentric pair 17 in V. aurea and on the short arms of the metacentric pair 9 in T. rhomboides. Furthermore, V. aurea showed four telomeric histone gene clusters on three metacentric pairs, at both ends of chromosome 2 and on the long arms of chromosomes 3 and 8, whereas histone genes in T. rhomboides clustered interstitially on the long arms of the metacentric pair 5 and proximally on the long arms of the subtelocentric pair 12. Double and triple FISH experiments demonstrated that rDNA and H3 histone genes localized on different chromosome pairs in the two clam species. Telomeric signals were found at both ends of every single chromosome in both species. Chromosomal location of these three gene families in two species of Veneridae provides a clue to karyotype evolution in this commercially important bivalve family.     

Chromosome phylogeny of <Emphasis Type="Italic">Zamia</Emphasis> and <Emphasis Type="Italic">Ceratozamia</Emphasis> by means of Robertsonian changes detected by fluorescence <Emphasis Type="Italic">in situ</Emphasis> hybridization (FISH) technique of rDNA

 Appearance and location of 45S rDNA and 5S rDNA signals were compared in chromosomes of nine species of the aneuploid Zamia and their taxonomically and phylogenetically closely related Ceratozamia mexicana. The 45S rDNA signal was detected in the proximal region of six chromosomes in Zamia angustifolia, Z. integrifolia, Z. pumila and Z. pygmaea (all 2n=16); in the proximal region of 6–14 chromosomes in Z. furfuracea, Z. loddigesii, Z. skinneri and Z. vazquezii (all 2n=18); and on the proximal region of 20 chromosomes in Z. muricata (2n=23). The 5S rDNA signals were commonly seen near the terminal region of the short arm of two metacentric chromosomes in the four species with 2n=16 and Z. furfuracea, Z. loddigesii and Z. vazquezii with 2n=18. Other 5S rDNA signals were seen near the terminal region of two terminal-centromeric chromosomes in Z. skinneri and near the terminal region of a metacentric and a telocentric chromosomes in Z. muricata. In contrast, those with 45S and 5S rDNA signals were exhibited in chromosomes of Ceratozamia mexicana in a different manner from those in the nine species of Zamia; the 45S rDNA signal in the terminal region of four metacentric and two submetacentric chromosomes and the 5S rDNA signal near the proximal region of two metacentric chromosomes. Received November 1, 1999 Accepted January 10, 2001     

A simple chromosomal marker can reliably distinguishes <Emphasis Type="Italic">Poncirus</Emphasis> from <Emphasis Type="Italic">Citrus</Emphasis> species

Several chromosome types have been recognized in Citrus and related genera by chromomycin A₃ (CMA) banding patterns and fluorescent in situ hybridization (FISH). They can be used to characterize cultivars and species or as markers in hybridization and backcrossing experiments. In the present work, characterization of six cultivars of P. trifoliata (“Barnes”, “Fawcett”, “Flying Dragon”, “Pomeroy”, “Rubidoux”, “USDA”) and one P. trifoliata × C. limonia hybrid was performed by sequential analyses of CMA banding and FISH using 5S and 45S rDNA as probes. All six cultivars showed a similar CMA⁺ banding pattern with the karyotype formula 4B + 8D + 6F. The capital letters indicate chromosomal types: B, a chromosome with one telomeric and one proximal band; D, with only one telomeric band; F, without bands. In situ hybridization labeling was also similar among cultivars. Three chromosome pairs displayed a closely linked set of 5S and 45S rDNA sites, two of them co-located with the proximal band of the B type chromosomes (B/5S-45S) and the third one co-located with the terminal band of a D pair (D/5S-45S). The B/5S-45S chromosome has never been found in any citrus accessions investigated so far. Therefore, this B chromosome can be used as a marker to recognize the intergeneric Poncirus × Citrus hybrids. The intergeneric hybrid analyzed here displayed the karyotype formula 4B + 8D + 6F, with two chromosome types B/5S-45S and two D/5S-45S. The karyotype formula and the presence of two B/5S-45S chromosomes clearly indicate that the plant investigated is a symmetric hybrid. It also demonstrates the suitability of karyotype analyses to differentiate zygotic embryos or somatic cell fusions involving trifoliate orange germplasm. During the submission of this paper, we analyzed 25 other citrus cultivars with the same methodology and we found that the chromosome marker reported here can indeed distinguish Poncirus trifoliata from grapefruits, pummelos, and one variegated access of Citrus, besides the previously reported access of limes, limons, citrons, and sweet-oranges. However, among 14 mandarin cultivars, two of them displayed a single B/5S-45S chromosome, whereas in Citrus hystrix D.C., a far related species belonging to the Papeda subgenus, this chromosome type was found in homozygosis. Since these two mandarin cultivars are probably of hybrid origin, we assume that for almost all commercial cultivars and species of the subgenus Citrus this B type chromosome is a useful genetic marker.     

Cytotaxonomical analysis of <Emphasis Type="Italic">Momordica</Emphasis> L. (Cucurbitaceae) species of Indian occurrence

Somatic chromosome number and detailed karyotype analysis were carried out in six Indian Momordica species viz. M. balsamina, M. charantia, M. cochinchinensis, M. dioica, M. sahyadrica and M. cymbalaria (syn. Luffa cymbalaria; a taxon of controversial taxonomic identity). The somatic chromosome number 2n = 22 was reconfirmed in monoecious species (M. balsamina and M. charantia). Out of four dioecious species, the chromosome number was reconfirmed in M. cochinchinensis (2n = 28), M. dioica (2n = 28) and M. subangulata subsp. renigera (2n = 56), while in M. sahyadrica (2n = 28) somatic chromosome number was reported for the first time. A new chromosome number of 2n = 18 was reported in M. cymbalaria against its previous reports of 2n = 16, 22. The karyotype analysis of all the species revealed significant numerical and structural variations of chromosomes. It was possible to distinguish chromosomes of M. cymbalaria from other Momordica species and also between monoecious and dioecious taxa of the genus. Morphology and crossability among the dioecious species was also studied. Evidence from morphology, crossability, pollen viability and chromosome synapsis suggests a segmental allopolyploid origin for M. subangulata subsp. renigera. The taxonomic status of the controversial taxon M. cymbalaria was also discussed using morphological, karyological and crossability data.     

Molecular cytogenetics of <Emphasis Type="Italic">Oligosarcus hepsetus</Emphasis> (Teleostei,Characiformes) from two Brazilian locations

Karyotype and cytogenetic markers of Oligosarcus hepsetus from two Brazilian locations in the Paraíba do Sul River Basin (Brazil) were investigated using differential staining techniques (C-banding, silver (Ag)- and chromomycin A₃ (CMA₃)-staining) and fluorescent in situ hybridization (FISH) using 18 S rDNA and 5 S rDNA probes. The diploid chromosome number was invariably 2n = 50 with 3 pairs of metacentric, 5 pairs of submetacentric, 8 pairs of subtelocentric and 9 pairs of acrocentric chromosomes. No heteromorphic sex chromosomes were observed. The nucleolar organizer regions (NORs) were detected in the short arms of the largest acrocentric pair using Ag-, CMA₃- stainings and FISH with 18 S rDNA probe, the latter showing also positive labeling in the short arms of a small acrocentric pair, not visualized by the former methods. FISH with 5 S rDNA probe showed positive labeling in the two chromosome pairs. While the CMA₃-staining exhibited GC-rich heterochromatin segments in two pairs of chromosomes, including those coincided with Ag-NORs, the DAPI staining did not reveal any signal, indicating the absence of AT-rich heterochromatin. FISH with an As-51 satellite DNA probe derived from the closely related Astyanax scabripinnis did not reveal any positive signal, demonstrating the absence of this class of DNA in the genome of the specimens under study.     

Comparative cytogenetic analysis of four species of <Emphasis Type="Italic">Dendropsophus</Emphasis> (Hylinae) from the Brazilian Atlantic forest

We conducted a cytogenetic study of four hyline frog species (Dendropsophus elegans, D. microps, D. minutus and D. werneri) from southern Brazil. All species had 2n = 30 chromosomes, with interspecific and intraspecific variation in the numbers of metacentric, submetacentric, subtelocentric and telocentric chromosomes. C-banding and fluorochrome staining revealed conservative GC-rich heterochromatin localized in the pericentromeric regions of all species. The location of the nucleolus organizer regions, as confirmed by fluorescent in situ hybridization, differed between species. Telomeric probes detected sites that were restricted to the terminal regions of all chromosomes and no interstitial or centromeric signals were observed. Our study corroborates the generic synapomorphy of 2n = 30 chromosomes for Dendropsophus and adds data that may become useful for future taxonomic revisions and a broader understanding of chromosomal evolution among hylids.     

A karyological study of swamp and dry valley populations of Siberian fir (<Emphasis Type="Italic">Abies sibirica</Emphasis> Ledeb.)

The karyological data on populations of Siberian fir (Abies sibirica Ledeb.) growing in lowland swamp and dry valleys are given. The diploid set of both populations included 24 chromosomes (2n = 24). Polykaryogram analysis revealed seven pairs of metacentric and five pairs of submetacentric chromosomes. The revealed differences between the populations included the absolute length of chromosomes, number of nucleolar organizer regions, and number of nucleoli. Changed chromosome numbers (mixoploidy and aneuploidy) as well as chromosomal aberrations were recorded. For the first time, mitosis was studied in this species and anaphase/telophase aberrations were revealed. The population of Siberian fir growing under extreme conditions of lowland swamp featured the widest range of mutations.Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 1, 2005, pp. 23–29.Original Russian Text Copyright © 2005 by Sedelnikova, Pimenov.     

The origin of an unusual sex chromosome constitution in <Emphasis Type="Italic">Acomys</Emphasis> sp. (Rodentia,Muridae) from Tanzania

This paper describes a case which presents an evident variation from the “standard” XX/XY sex chromosomal constitution in a rodent, Acomys sp. This species known to be found in three localities of East Africa has only recently been separated from A. spinosissimus, its closest relative. In our study, five specimens of Acomys sp. and eight specimens of A. spinosissimus were live-trapped in five localities. Comparisons between the two taxa assed by G- banding show a complete homology in the chromosomal shape and banding pattern for 29 pairs of chromosomes corresponding to the complete autosomal set of A. spinosissimus. However, while all the A. spinosissimus analysed have 2n = 60 and a XY-XX system, in Acomys sp. males and females constitute mosaics for sex chromosomes in the bone marrow cells. Females (2n = 59, 60) have an excess (97%) of aneuploid cells with one single giant X chromosome, and males (2n = 60, 61) show X0/XY cells occurring in somatic tissues and XY cells in the germinal lineage. In addition, an odd heterochromatic submetacentric chromosome was identified in all the cells examined in two males and a female of Acomys sp. Since this chromosome was not related to sex determination and it is not present in all the analysed specimens, it can be considered as a B chromosome. Finally, the in situ fluorescence hybridisation (FISH) with telomeric probes showed a very intense interstitial telomeric signal (ITS) at the medial part on the long heterochromatic arm of the X chromosome. This could be due to recent chromosomal rearrangement.