Occurrence of a Metacentric Macrochromosome B in Different Species of the Genus Astyanax (Pisces, Characidae, Tetragonopterinae).

Moreira‐Filho, Orlando; Fenocchio, Alberto Sérgio; Pastori, María Cristina; Bertollo, L.A.C.

doi:10.1508/cytologia.66.59

Cited by 36 publications

(31 citation statements)

References 13 publications

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“…The analysis of constitutive heterochromatin patterns showed heterochromatic blocks in the pericentromeric regions of most chromosomes and evident signals in the terminal regions of some chromosomes (Figure 2), similar to those found in other populations of A. bockmanni (Kavalco et al 2009;Hashimoto and Porto-Foresti 2010). In relation to the B chromosomes, all three morphological variants (B M , B m , and B a ) were identified as heterochromatic (Figure 2), in accordance with a common characteristic reported for B chromosomes in the genus Astyanax (Néo et al 2000;Moreira-Filho et al 2001;Hashimoto et al 2008;Machado et al 2012).…”

Section: Resultssupporting

confidence: 87%

“…a macrochromosome (B M ) similar in size to chromosome pair 1 and a microchromosome (B m ) similar in size to B a (Table 1 and Figure 2). Distinct B chromosomes have been described in several species of the genus Astyanax, and the most frequent variant is the metacentric macrochromosome (B M ) similar to chromosome pair 1, which might be considered the ancestral B chromosome with probably an early origin preceding the species differentiation (Moreira-Filho et al 2001;Vicari et al 2011;Machado et al 2012).…”

Section: Resultsmentioning

confidence: 99%

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Cytogenetic characterization of distinct B chromosomes in a population of the fish Astyanax bockmanni (Teleostei, Characiformes)

et al. 2012

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Individuals of Astyanax bockmanni from one population belonging to the Paranapanema River basin, southeastern Brazil, were cytogenetically examined. In the present paper, we report a diploid number of 50 chromosomes, with some individuals bearing additional chromosomes, characterized as different variants of B chromosomes. The B microchromosome of acrocentric morphology (B a ) was the most frequent type in this population (77.7%). Two other variants were identified as metacentric B chromosomes, but of distinct sizes, characterized as macrochromosome (B M ) and microchromosome (B m ). Conspicuous heterochromatic blocks were observed in the terminal regions of some chromosomes of the standard karyotype and partially heterochromatic blocks were detected in all B chromosomes. 18S ribosomal RNA genes were distributed in the terminal region of several chromosomes, but were not located on the B chromosomes.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Cytogenetic characterization of distinct B chromosomes in a population of the fish Astyanax bockmanni (Teleostei, Characiformes)

et al. 2012

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“…Such general heterochromatin pattern has frequently been observed in distinct populations of A. altiparanae (Daniel-Silva and Almeida-Toledo, 2001;Fernandes and Martins-Santos, 2004), demonstrating that these chromosomal regions present a highly conservative distribution in this species. The supernumerary chromosome was totally heterochromatic (Figure 2), in accordance with a common feature reported for B chromosomes in the genus Astyanax (Salvador and Moreira-Filho, 1992; Mizoguchi and Martins-Santos, 1997; Néo et al, 2000a, b;Moreira-Filho et al, 2001).…”

supporting

confidence: 86%

“…Although A. scabripinnis reveals B chromosomes of different morphology and size, a metacentric B macrochromosome (B M ) has been found to be a common feature in most of the analyzed populations with supernumerary chromosomes (Moreira-Filho et al, 2004). Additionally, a similar B M chromosome has been found in other three species of the same genus (A. eigenmanniorum, A. fasciatus, and A. schubarti), suggesting that this B M variant might have preceded the differentiation of these species (Moreira-Filho et al, 2001). Thus, considering this hypothesis, the B microchromosome of A. altiparanae appears to have an independent origin of the B M variant found in other Astyanax species and can represent a sporadic case in this species.…”

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confidence: 83%

First report of a B chromosome in a natural population of Astyanax altiparanae (Characiformes, Characidae)

et al. 2008

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Several species of the genus Astyanax have already been genetically studied, and B-chromosomes have been considered to be an interesting feature in some species of this group. In the present paper we report, for the first time, the occurrence of a B microchromosome in a natural population of A. altiparanae. This additional genomic element was identified as an acrocentric chromosome, similar in size to the smallest chromosomal pairs of the standard karyotype. Analysis of the constitutive heterochromatin pattern by C-banding evidenced heterochromatic blocks located on centromeric, pericentromeric, and interstitial regions of some chromosomes, and also positive marks in a subtelocentric chromosomal pair that presented the short arms entirely heterochromatic. The application of this methodology also revealed a heterochromatic pattern in the extra chromosome, a typical feature of supernumerary chromosomes.

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“…It is worth pointing out that the specimen from rio Cará-cará with 2n=49 chromosomes has a basic karyotypic structure and a constitutive heterochromatin distribution pattern similar to those of cytotypes A and B (Fig. 3b), therefore representing a possible rare hybridization event between these cytotypes, or less probably a case of extra chromosomes (B-chromosomes), as already seen in a few Astyanax species (Moreira-Filho et al, 2001). In Astyanax scabripinnis, Souza & Moreira-Filho (1995) and Maistro et al (2000) also verified the occurrence of sympatric cytotypes, not dismissing the possibility that this condition is the consequence of a secondary contact of originally allopatric populations.…”

Section: Et Al 2003) As Is Also Observed In Astyanax Scabripinnissupporting

confidence: 55%

Astyanax aff. fasciatus Cuvier, 1819 (Teleostei; Characidae): evidences of a species complex in the upper rio Tibagi basin (Paraná, Brazil)

et al. 2006

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Four populations of Astyanax aff. fasciatus of the upper rio Tibagi (municipal district of Ponta Grossa, Paraná State, Brazil), had their karyotypes and morphometry analyzed. The cytogenetic data show the occurrence of distinct karyotypes (cytotypes), here named cytotype A, with 2n=48 chromosomes (6m+18sm+14st+10a), cytotype B, with 2n=50 chromosomes (8m+18sm+14st+10a) and cytotype C, with 2n=50 chromosomes (8m+18sm+14st+10a). The distribution pattern of the constitutive heterochromatin was very similar between cytotypes A and B, but diverged in relation to cytotype C. Distinct cytotypes may occur in sympatry in the upper rio Tibagi region, with the exception of the Furna 2 sample, which presents cytotype A exclusively. In addition, a specimen with 2n=49 chromosomes (7m+18sm+14st+10a) was also found and, by the characteristics presented, may be a consequence of a rare hybridization event between cytotypes A and B. The morphometric analyses of canonical variates indicate a consistent isolation of the Furna 2 sample, while the other samples seem to be superimposed, indicating a possible gene flow or even a recent isolation event. This model points to a probable complex of cryptic species in the studied region.Quatro populações de Astyanax aff. fasciatus do alto rio Tibagi (município de Ponta Grossa, Paraná, Brasil) foram citogeneticamente e morfometricamente analisadas. Os dados citogenéticos mostram a ocorrência de distintos cariótipos (citótipos), aqui nomeados citótipo A, com 2n=48 (6m+18sm+14st+10a), citótipo B, com 2n=50 (8m+18sm+14st+10a) e citótipo C, com 2n=50 cromossomos (8m+18sm+14st+10a). O padrão de distribuição da heterocromatina constitutiva foi muito similar entre os citótipos A e B, mas mostrou-se divergente em relação ao citótipo C. Citótipos distintos podem ocorrer em simpatria na região do alto rio Tibagi, com exceção da amostra da Furna 2, a qual apresenta somente o citótipo A exclusivamente. Além disso, um exemplar com 2n=49 cromoossomos (7m+18sm+14st+10a) foi também encontrado e, pelas características apresentadas, pode ser uma conseqüência de um raro evento de hibridização entre os citótipos A e B. As análises morfométricas de variáveis canônicas indicam um isolamento consistente da amostra da Furna 2 enquanto as demais amostras analisadas se apresentam sobrepostas indicando um possível fluxo gênico ou evento de isolamento recente. Este modelo aponta para um complexo de espécies crípticas na região estudada.

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Occurrence of a Metacentric Macrochromosome B in Different Species of the Genus Astyanax (Pisces, Characidae, Tetragonopterinae).

Cited by 36 publications

References 13 publications

Cytogenetic characterization of distinct B chromosomes in a population of the fish Astyanax bockmanni (Teleostei, Characiformes)

Cytogenetic characterization of distinct B chromosomes in a population of the fish Astyanax bockmanni (Teleostei, Characiformes)

First report of a B chromosome in a natural population of Astyanax altiparanae (Characiformes, Characidae)

Astyanax aff. fasciatus Cuvier, 1819 (Teleostei; Characidae): evidences of a species complex in the upper rio Tibagi basin (Paraná, Brazil)

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