We present the first cytogenetic data for
and
with the aim of (1) investigating evolutionary events within
and their relationships with other Lebiasinidae genera and (2) checking the evolutionary ...relationships between Lebiasinidae and Ctenoluciidae. Both species have a diploid number 2n = 36 with similar karyotypes and microsatellite distribution patterns but present contrasting C-positive heterochromatin and CMA
banding patterns. The remarkable interstitial series of C-positive heterochromatin occurring in
is absent in
. Accordingly,
shows the ribosomal DNA sites as the only GC-rich (CMA
) regions, while
shows evidence of a clear intercalated CMA
banding pattern. In addition, the multiple 5S and 18S rDNA sites in
contrast with single sites present in
. Comparative genomic hybridization (CGH) experiments also revealed a high level of genomic differentiation between both species. A polymorphic state of a conspicuous C-positive, CMA
, and (CGG)n band was found only to occur in
females, and its possible relationship with a nascent sex chromosome system is discussed. Whole chromosome painting (WCP) and CGH experiments indicate that the
species examined and
share similar chromosomal sequences, thus supporting the relatedness between them and the evolutionary relationships between the Lebiasinidae and Ctenoluciidae families.
The Amazon aquatic ecosystems have been modified by the human population growth, going through changes in their water bodies and aquatic biota. The spectacled alligator (Caiman crocodilus crocodilus) ...has a wide distribution and adaptability to several environments, even those polluted ones. This study aimed to investigate if a Caiman species living in urban streams of Manaus city (Amazonas State, Brazil) is affected by environmental pollution. For that, it was used classical and molecular cytogenetic procedures, in addition to micronucleus and comet assays. Although the karyotype macrostructure remains unaltered (2 n = 42 chromosomes; 24 t + 18 m/sm; NF = 60), the genotoxic analysis and the cytogenetic mapping of repetitive DNA sequences demonstrated that polluted environments alter the genome of the specimens, affecting both the chromosomal organization and the genetic material.
•The effects of domestic effluents on the spectacled caiman in the Amazon streams.•Chromosomal analysis in Caiman c. crocodilus that occur in polluted and unpolluted environments.•The higher frequency of micronucleus and comets in the organisms who lives in polluted streams showing a great DNA damage.
Notopteridae (Teleostei, Osteoglossiformes) represents an old fish lineage with ten currently recognized species distributed in African and Southeastern Asian rivers. Their karyotype structures and ...diploid numbers remained conserved over long evolutionary periods, since African and Asian lineages diverged approximately 120 Mya. However, a significant genetic diversity was already identified for these species using molecular data. Thus, why the evolutionary relationships within Notopteridae are so diverse at the genomic level but so conserved in terms of their karyotypes? In an attempt to develop a more comprehensive picture of the karyotype and genome evolution in Notopteridae, we performed comparative genomic hybridization (CGH) and cross-species (Zoo-FISH) whole chromosome painting experiments to explore chromosome-scale intergenomic divergence among seven notopterid species, collected in different African and Southeast Asian river basins. CGH demonstrated an advanced stage of sequence divergence among the species and Zoo-FISH experiments showed diffuse and limited homology on inter-generic level, showing a temporal reduction of evolutionarily conserved syntenic regions. The sharing of a conserved chromosomal region revealed by Zoo-FISH in these species provides perspectives that several other homologous syntenic regions have remained conserved among their genomes despite long temporal isolation. In summary, Notopteridae is an interesting model for tracking the chromosome evolution as it is (i) ancestral vertebrate group with Gondwanan distribution and (ii) an example of animal group exhibiting karyotype stasis. The present study brings new insights into degree of genome divergence vs. conservation at chromosomal and sub-chromosomal level in representative sampling of this group.
The catfish family Siluridae contains 107 described species distributed in Asia, but with some distributed in Europe. In this study, karyotypes and other chromosomal characteristics of 15 species ...from eight genera were examined using conventional and molecular cytogenetic protocols. Our results showed the diploid number (2
) to be highly divergent among species, ranging from 2
= 40 to 92, with the modal frequency comprising 56 to 64 chromosomes. Accordingly, the ratio of uni- and bi-armed chromosomes is also highly variable, thus suggesting extensive chromosomal rearrangements. Only one chromosome pair bearing major rDNA sites occurs in most species, except for
,
, and
with two; and
with five such pairs. In contrast, chromosomes bearing 5S rDNA sites range from one to as high as nine pairs among the species. Comparative genomic hybridization (CGH) experiments evidenced large genomic divergence, even between congeneric species. As a whole, we conclude that karyotype features and chromosomal diversity of the silurid catfishes are unusually extensive, but parallel some other catfish lineages and primary freshwater fish groups, thus making silurids an important model for investigating the evolutionary dynamics of fish chromosomes.
The Neotropical fish,
Hoplias malabaricus
, is one of the most cytogenetically studied fish taxon with seven distinct karyomorphs (A–G) comprising varying degrees of sex chromosome differentiation, ...ranging from homomorphic to highly differentiated simple and multiple sex chromosomes. Therefore, this fish offers a unique opportunity to track evolutionary mechanisms standing behind the sex chromosome evolution and differentiation. Here, we focused on a high-resolution cytogenetic characterization of the unique XX/XY
1
Y
2
multiple sex chromosome system found in one of its karyomorphs (G). For this, we applied a suite of conventional (Giemsa-staining, C-banding) and molecular cytogenetic approaches, including fluorescence in situ hybridization FISH (with 5S and 18S rDNAs, 10 microsatellite motifs and telomeric (TTAGGG)
n
sequences as probes), comparative genomic hybridization (CGH), and whole chromosome painting (WCP). In addition, we performed comparative analyses with other Erythrinidae species to discover the evolutionary origin of this unique karyomorph G-specific XY
1
Y
2
multiple sex chromosome system. WCP experiments confirmed the homology between these multiple sex chromosomes and the nascent XX/XY sex system found in the karyomorph F, but disproved a homology with those of karyomorphs A–D and other closely related species. Besides, the putative origin of such XY
1
Y
2
system by rearrangements of several chromosome pairs from an ancestral karyotype was also highlighted. In addition, clear identification of a male-specific region on the Y
1
chromosome suggested a differential pattern of repetitive sequences accumulation. The present data suggested the origin of this unique XY
1
Y
2
sex system, revealing evidences for the high level of plasticity of sex chromosome differentiation within the Erythrinidae.
Characterizing the abundance and genomic distribution of repetitive DNAs provides information on genome evolution, especially regarding the origin and differentiation of sex chromosomes. Triportheus ...fishes offer a useful model to explore the evolution of sex chromosomes, since they represent a monophyletic group in which all species share a ZZ/ZW sex chromosome system. In this study, we analyzed the distribution of 13 classes of repetitive DNA sequences by FISH, including microsatellites, rDNAs, and transposable elements in 6 Triportheus species, in order to investigate the fate of the sex-specific chromosome among them. These findings show the dynamic differentiation process of the W chromosome concerning changes in the repetitive DNA fraction of the heterochromatin. The differential accumulation of the same class of repeats on this chromosome, in both nearby and distant species, reflects the inherent dynamism of the microsatellites, as well as the plasticity that shapes the evolutionary history of the sex chromosomes, even among closely related species sharing a same sex chromosome system.
Neotropical cichlid fishes are one of the most diversified and evolutionarily successful species assemblages. Extremely similar forms and intraspecific polychromatism present challenges for the ...taxonomy of some of these groups. Several species complexes have a largely unknown origin and unresolved evolutionary processes. Dwarf cichlids of the genus
, comprising more than a hundred species, exhibit intricate taxonomic and biogeographic patterns, with both allopatric and sympatric distributions. However, karyotype evolution and the role of chromosomal changes in
are still unknown. In the present study, nine South American
species were analyzed using conventional cytogenetic methods and the mapping of repetitive DNA sequences 18S rDNA, 5S rDNA, and (TTAGGG)n by fluorescence in situ hybridization (FISH). Our results showed that
has unique cytogenetic characteristics in relation to closely related groups, such as a reduced 2n and a large number of bi-armed chromosomes. Interspecific patterns revealed a scenario of remarkable karyotypic changes, including a reduction of 2n, the occurrence of B-chromosomes and evolutionary dynamic of rDNA tandem repeats. In addition to the well-known pre-zygotic reproductive isolation, the karyotype reorganization in the genus suggests that chromosomal changes could act as postzygotic barriers in areas where
congeners overlap.
Osteoglossiformes represents one of the most ancestral teleost lineages, currently widespread over almost all continents, except for Antarctica. However, data involving advanced molecular ...cytogenetics or comparative genomics are yet largely limited for this fish group. Therefore, the present investigations focus on the osteoglossiform family Arapaimidae, studying a unique fish model group with advanced molecular cytogenetic genomic tools. The aim is to better explore and clarify certain events and factors that had impact on evolutionary history of this fish group. For that, both South American and African representatives of Arapaimidae, namely Arapaima gigas and Heterotis niloticus, were examined. Both species differed markedly by diploid chromosome numbers, with 2n = 56 found in A. gigas and 2n = 40 exhibited by H. niloticus. Conventional cytogenetics along with fluorescence in situ hybridization revealed some general trends shared by most osteoglossiform species analyzed thus far, such as the presence of only one chromosome pair bearing 18S and 5S rDNA sites and karyotypes dominated by acrocentric chromosomes, resembling thus the patterns of hypothetical ancestral teleost karyotype. Furthermore, the genomes of A. gigas and H. niloticus display remarkable divergence in terms of repetitive DNA content and distribution, as revealed by comparative genomic hybridization (CGH). On the other hand, genomic diversity of single copy sequences studied through principal component analyses (PCA) based on SNP alleles genotyped by the DArT seq procedure demonstrated a very low genetic distance between the South American and African Arapaimidae species; this pattern contrasts sharply with the scenario found in other osteoglossiform species. Underlying evolutionary mechanisms potentially explaining the obtained data have been suggested and discussed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Satellites are an abundant source of repetitive DNAs that play an essential role in the chromosomal organization and are tightly linked with the evolution of sex chromosomes. Among fishes, ...Triportheidae stands out as the only family where almost all species have a homeologous ZZ/ZW sex chromosomes system. While the Z chromosome is typically conserved, the W is always smaller, with variations in size and morphology between species. Here, we report an analysis of the satellitome of
Triportheus auritus
(TauSat) by integrating genomic and chromosomal data, with a special focus on the highly abundant and female-biased satDNAs. In addition, we investigated the evolutionary trajectories of the ZW sex chromosomes in the Triportheidae family by mapping satDNAs in selected representative species of this family. The satellitome of
T. auritus
comprised 53 satDNA families of which 24 were also hybridized by FISH. Most satDNAs differed significantly between sexes, with 19 out of 24 being enriched on the W chromosome of
T. auritus
. The number of satDNAs hybridized into the W chromosomes of
T. signatus
and
T. albus
decreased to six and four, respectively, in accordance with the size of their W chromosomes. No TauSat probes produced FISH signals on the chromosomes of
Agoniates halecinus.
Despite its apparent conservation, our results indicate that each species differs in the satDNA accumulation on the Z chromosome. Minimum spanning trees (MSTs), generated for three satDNA families with different patterns of FISH mapping data, revealed different homogenization rates between the Z and W chromosomes
.
These results were linked to different levels of recombination between them. The most abundant satDNA family (TauSat01) was exclusively hybridized in the centromeres of all 52 chromosomes of
T. auritus
, and its putative role in the centromere evolution was also highlighted. Our results identified a high differentiation of both ZW chromosomes regarding satellites composition, highlighting their dynamic role in the sex chromosomes evolution.
Lebiasinidae is a small fish family composed by miniature to small-sized fishes with few cytogenetic data (most of them limited to descriptions of diploid chromosome numbers), thus preventing any ...evolutionary comparative studies at the chromosomal level. In the present study, we are providing, the first cytogenetic data for the red spotted tetra, Copeina guttata, including the standard karyotype, C-banding, repetitive DNA mapping by fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH), providing chromosomal patterns and novel insights into the karyotype differentiation of the family. Males and females share diploid chromosome number 2n = 42 and karyotype composed of 2 metacentric (m), 4 submetacentric (sm) and 36 subtelocentric to acrocentric (st-a) chromosomes. Blocks of constitutive heterochromatin were observed in the centromeric and interstitial regions of several chromosomes, in addition to a remarkably large distal block, heteromorphic in size, which fully corresponded with the 18S rDNA sites in the fourth chromosomal pair. This overlap was confirmed by 5S/18S rDNA dual-color FISH. On the other hand, 5S rDNA clusters were situated in the long and short arms of the 2nd and 15th pairs, respectively. No sex-linked karyotype differences were revealed by male/female CGH experiments. The genomic probes from other two lebiasinid species, Lebiasina melanoguttata and Pyrrhulina brevis, showed positive hybridization signals only in the NOR region in the genome of C. guttata. We demonstrated that karyotype diversification in lebiasinids was accompanied by a series of structural and numeric chromosome rearrangements of different types, including particularly fusions and fissions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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