Chromosomal Variability among Allopatric Populations of Erythrinidae Fish Hoplias malabaricus: Mapping of Three Classes of Repetitive DNAs (original) (raw)
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BMC Genetics, 2009
Background Seven karyomorphs of the fish, Hoplias malabaricus (A-G) were previously included in two major groups, Group I (A, B, C, D) and Group II (E, F, G), based on their similar karyotype structure. In this paper, karyomorphs from Group I were analyzed by means of distinct chromosomal markers, including silver-stained nucleolar organizer regions (Ag-NORs) and chromosomal location of repetitive sequences (18S and 5S rDNA, and satellite 5SHind III-DNA), through fluorescence in situ hybridization (FISH), in order to evaluate the evolutionary relationships among them. Results The results showed that several chromosomal markers had conserved location in the four karyomorphs. In addition, some other markers were only conserved in corresponding chromosomes of karyomorphs A-B and C-D. These data therefore reinforced and confirmed the proposed grouping of karyomorphs A-D in Group I and highlight a closer relationship between karyomorphs A-B and C-D. Moreover, the mapping pattern of some ...
Chromosome …, 2000
Hoplias malabaricus, a widely distributed neotropical freshwater fish, shows a conspicuous karyotypic diversification. An overview of this diversity is presented here comprising several Brazilian populations, and some others from Argentina, Uruguay and Surinam. Seven general cytotypes are clearly identified on the basis of their diploid number (2n=39 to 2n=42), chromosomal morphology and sex chromosome systems, which can be clustered into two major karyotypic groups. This clustering suggests that karyotype structure would be more informative than the diploid number regarding cytotype relationships in this fish group. While some cytotypes show a wide geographical distribution, some others appear to be endemic to specific hydrographic basins. Sympatric cytotypes can occur without detection of hybrid forms; this situation points to a lack of gene flow, a fact that is also reinforced by studies with genomic markers. The karyotypic data support the view that the nominal taxon H. malabaricus corresponds to a species complex comprising distinct evolutionary units, each with well-established chromosomal differences.
Cytogenetic and Genome Research, 2009
Six populations of Hoplias malabaricus from the Lower Paranapanema River were studied and showed 2n = 40 with metacentric/submetacentric chromosomes for females and 2n = 39 with m/sm chromosomes for males, thereby revealing a multiple sex chromosome system of the X1X1X2X2/X1X2Y type. The Y chromosome was the largest metacentric chromosome in all karyotypes. The heterochromatic blocks were located in a pericentromeric region of all pairs and in telomeric regions in some other pairs. A conspicuous pericentromeric C-band was detected in a single pair, equivalent to the X1 chromosome. No markers on X2 chromosomes were detected, but they could be identified by their size. The females displayed the same distribution of C and chromomycin A3 bands and 18S rDNA sites among the populations. However, the males exhibited differences in both number and position of Giemsa C-bands on the Y chromosome, which were also evident after Chromomycin A3 banding and FISH with the 18S rDNA probe. These cyto...
Chromosome Research, 1993
The chromosomes of the primitive South American teleost fish Hoplias malabaricus have been analyzed by classical cytogenetic (C-, AgNOR-, Hoechst 33258-, and Q-banding) techniques. A highly repetitive DNA family has been cloned and sequenced. It is a tandemly repeated sequence of about 355 bp, yielding an overall base pair composition of 67% AT with long runs of >50% As and 70% Ts. Analysis of sequence variation has allowed the further categorization of Hoplias
Zebrafish
Hoplias malabaricus is one of the most widespread freshwater fish in the Neotropics; all karyotyped populations exhibit diploid numbers ranging from 2n = 39 to 2n = 42, with variations that make up to seven karyomorphs, suggesting the existence of a species complex or paraspecies. In this study, we explored the diversity of H. malabaricus of the Magdalena River Basin using karyotypic analysis. Cytogenetic analyses were carried out on 32 specimens and six sample sites from the upper, middle, and lower Magdalena River, a trans-Andean basin in Colombia, using standard and molecular techniques and fluorescence in situ hybridization (FISH). The upper and middle Magdalena samples were 2n = 42 and showed unique fluorescence patterns, whereas the lower Magdalena samples had 2n = 40, generalized fluorescence patterns, and one specimen with a mosaic karyotype and heteromorphic chromosome pair. The genetic discontinuity along the Magdalena River fits the museum hypothesis, where the 2n = 42A predates the modern configuration of the Magdalena Basin in the Late Miocene, and the 2n = 40C karyomorph represents a more derived condition. Our results underline the complex biogeography of the trans-Andean region, where the Magdalena-Cauca Basin should be considered a freshwater fauna mosaic with divergent evolutionary affinities.
Genetica, 2006
A substantial fraction of the eukaryotic genome consists of repetitive DNA sequences that include satellites, minisatellites, microsatellites, and transposable elements. Although extensively studied for the past three decades, the molecular forces that generate, propagate and maintain repetitive DNAs in the genomes are still discussed. To further understand the dynamics and the mechanisms of evolution of repetitive DNAs in vertebrate genome, we searched for repetitive sequences in the genome of the fish species Hoplias malabaricus. A satellite sequence, named 5SHindIII-DNA, which has a conspicuous similarity with 5S rRNA genes and spacers was identified. FISH experiments showed that the 5S rRNA bona fide gene repeats were clustered in the interstitial position of two chromosome pairs of H. malabaricus, while the satellite 5SHindIII-DNA sequences were clustered in the centromeric position in nine chromosome pairs of the species. The presence of the 5SHindIII-DNA sequences in the centromeres of several chromosomes indicates that this satellite family probably escaped from the selective pressure that maintains the structure and organization of the 5S rDNA repeats and become disperse into the genome. Although it is not feasible to explain how this sequence has been maintained in the centromeric regions, it is possible to hypothesize that it may be involved in some structural or functional role of the centromere organization.
Genetics and Molecular Biology, 2016
Hoplias malabaricus is a common fish species occurring in white, black and clear water rivers of the Amazon basin. Its large distribution across distinct aquatic environments can pose stressful conditions for dispersal and creates possibilities for the emergence of local adaptive profiles. We investigated the chromosomal localization of repetitive DNA markers (constitutive heterochromatin, rDNA and the transposable element REX-3) in populations from the Amazonas river (white water), the Negro river (black water) and the Tapajós river (clear water), in order to address the variation/association of cytogenomic features and environmental conditions. We found a conserved karyotypic macrostructure with a diploid number of 40 chromosomes (20 metacentrics + 20 submetacentrics) in all the samples. Heteromorphism in pair 14 was detected as evidence for the initial differentiation of an XX/XY system. Minor differences detected in the amount of repetitive DNA markers are interpreted as possible signatures of local adaptations to distinct aquatic environments.
Neotropical Ichthyology, 2009
The species Hoplias malabaricus is a predator fish found in nearly all cis-Andean basins. From a cytogenetic point of view, this species comprises, at least, seven differentiated karyomorphs. Several localities have been formerly analyzed in Brazil, however, some regions, such as Bahia State, remain underrepresented. Recently, the Brazilian Environment Ministry classified both Itapicuru and Contas river basins (entirely located within Bahia territory) as priority conservation areas, whose biodiversity status lacks enough information. Therefore, the goal of the present work was to characterize, cytogenetically, populations of H. malabaricus from both basins, by using conventional staining, Ag-NOR and C-banding techniques. All specimens presented a diploid number of 2n = 40 with metacentric/submetacentric chromosomes, without differences between sexes, thereby representing the so-called "karyomorph F". The first metacentric pair presented a remarkably larger size in relation to the other pairs. The NORs were multiple, comprising the terminal region on long arms of two chromosomal pairs in both populations. However, the C-banding pattern was somewhat distinguishable between samples. Although sharing heterochromatic blocks at centromeric region of all chromosomes, the population from Itapicuru River basin appeared to have some more conspicuous blocks than those observed in the population from Contas River basin. The similar karyotype observed in both populations suggests a common geological history between them. The present results represent an advance in the knowledge about the cytogenetic pattern of H. malabaricus populations from poorly studied basins.
Genetics and Molecular Biology, 2006
Chromosomal studies were carried out on a population of the fish Hoplerythrinus unitaeniatus (jeju) from Prata river in the São Francisco river basin, Minas Gerais, Brazil using conventional Giemsa staining, C-banding, silver nitrate nucleolar organizer region (Ag-NOR) staining and fluorescent in situ hybridization (FISH) with 18S and 5S rDNA probes. We found a high degree of inter-and intra-individual variability with the identification of 2n = 50, 2n = 51 and 2n = 52 karyotypes at nearly the same frequency within the population. Intra-individual variation in chromosomal morphology and, consequently, karyotype formulae was also observed, chiefly in the specimens with 2n = 50 and 2n = 52 chromosomes. Ag-NORs and 18S rDNA sites also showed numerical and chromosomal variation similar to that found for the 5S rDNA sites. Some putative hypotheses are considered in order to explain these results.