Intraspecific crosses resulting in the first occurrence of eight and nine B chromosomes in Prochilodus lineatus (Characiformes, Prochilodontidae)

B chromosomes are supernumerary elements present in about 15% of eukaryotic species and are most frequently heterochromatic, behave parasitically, show a transmission rate higher than standard (A) chromosomes, and can provoke harmful effects on carriers. In the current work, Prochilodus lineatus individuals carrying eight and nine B chromosomes were obtained by induced crossing performed involving breeders with different B chromosome numbers in their cells. The high B chromosome numbers found in the offspring were recorded for the first time in this species. The use of cytogenetic techniques applied in the present study revealed that regardless of the increase in number of B chromosomes in the genome of these individuals, those elements did not presented active genes, and showed their normal heterochromatic characteristic

Origem, herança e estrutura dos cromossomos supranumerários no gênero Prochilodus (Characiformes, Prochilodontidae)

A família Prochilodontidae apresenta uma extraordinária estabilidade dos caracteres morfológicos e merísticos, o qual pode estar relacionado ao fato de efetuarem grandes migrações com propósito reprodutivo, dispersando-se em grandes áreas. Sob o ponto de vista citogenético, apresenta uma constituição cariotípica bastante conservada com 2n=54 cromossomos dos tipos metacêntrico e submetacêntrico com número fundamental igual a 108. Além disso, a presença de microcromossomos supranumerários em algumas espécies do gênero Prochilodus tornou-se a base para diversos estudos citogenéticos. Diante disso, este trabalho objetivou realizar um estudo pormenorizado sobre a origem, herança e estrutura dos cromossomos supranumerários em Prochilodus. Para isto, foram realizados estudos citogenéticos envolvendo alguns exemplares deste gênero, portadores (Prochilodus lineatus e Prochilodus nigricans) e não-portadores de supranumerários (Prochilodus argenteus, Prochilodus brevis e Prochilodus costatus). Em todos os indivíduos analisados citogeneticamente foi constatado um número diploide de 54 cromossomos dos tipos metacêntrico e submetacêntrico, além da presença cromossomos B em P. lineatus e em P. nigricans. A utilização de marcadores citogenéticos convencionais (Giemsa, NOR e Banda C) e citogenéticos- moleculares (FISH) com sondas de genes ribossômicos 5S e 18S confirmaram uma constituição cariotípica conservada apenas para o número e morfologia cromossômica nestas cinco espécies. A localização das Regiões Organizadoras de Nucléolo (NOR) foi evidenciada no braço longo do segundo par de cromossomo submetacêntrico em P. brevis, P. costatus, P. lineatus e P. nigricans. Em P. argenteus somente um cromossomo deste mesmo par foi marcado pela Prata, seu homólogo não exibiu marcações demonstrando inatividade...The family Prochilodontidae shows morphological and meristic characters with an extraordinary degree of stability, which may be related to the great migrations accomplished for reproductive purposes, spreading over large areas. From the cytogenetic viewpoint, it presents a much conserved karyotypic constitution with 2n = 54 metacentric and submetacentric chromosomes with fundamental number equal to 108. Moreover, the presence of supernumerary microchromosomes in some species of the genus Prochilodus provided the basis for a range of cytogenetic studies. In light of the aforementioned, this study aimed to conduct a detailed investigation of the origin, inheritance, and structure of supernumerary chromosomes in Prochilodus. In this connection, we conducted cytogenetic studies involving a few specimens of this genus, bearers (Prochilodus lineatus and Prochilodus nigricans) and non-bearers of supernumerary (Prochilodus argenteus, Prochilodus brevis, and Prochilodus costatus). All subjects cytogenetically studied exhibited a diploid number of 54 metacentric and submetacentric chromosomes, besides revealing the presence B chromosomes in P. lineatus and P. nigricans. The use of conventional cytogenetic (Giemsa, NOR and C-Band) and molecular cytogenetic markers (FISH) with 5S and 18S ribosomal gene probes confirmed a conserved karyotypic constitution restricted only to the chromosome number and morphology in these five species. The location of Nucleolar Organizer Regions (NOR) was detected on the long arm of the second pair of a submetacentric chromosome in P. brevis, P. costatus, P. lineatus, and P. nigricans. In P. Argenteus, only one chromosome of that same pair was marked by silver staining, whereas its homologous did not show any markings, demonstrating inactivity in this region... (Complete abstract click electronic access below)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Cytogenetic Markers in Wild Population of Curimbata (Prochilodus lineatus) from Mogi-Guacu River

Within the genus Prochilodus, the species Prochilodus lineatus is certainly the most studied one from a cytogenetic point of view. In this study, a cytogenetic characterization of specimens of P. lineatus from Mogi-Guacu River was performed in the period from 2003 to 2007, through utilization of cytogenetic markers, such as Giemsa, Ag-NOR, C-banding and cytogenetical-molecular markers (FISH) to detect both 5S and 18S ribosomal genes. All analyzed individuals presented 2n=54 meta/submetacentric chromosomes, besides bearing up to 7 supernumerary Microchromosomes. Polymorphic NORs were detected on a single chromosomal pair. The constitutive heterochromatin was distributed at centromeric region of all chromosomes in the A complement, while the microchromosomes were totally heterochromatic. A syntenic distribution of 5S and 18S ribosomal genes was detected, comprising the NOR-bearing chromosomal pair. No additional ribosomal clusters in other chromosomes were observed. Although the karyotype features are commonly conserved within the genus Prochilodus, the few differences on the distribution of both ribosomal genes and heterochromatin when compared to specimens of P lineatus from other localities can be associated to the evolutionary changes that these repetitive sequences have undergone through the years

B-chromosome frequency stability in Prochilodus lineatus (Characiformes, Prochilodontidae)

The genus Prochilodus includes individuals ranging in size from medium to large, being highly relevant for commercial and subsistence fishing. Prochilodus species have a diploid number of 2n = 54 chromosomes and up to seven supernumerary (B) microchromosomes. Previous research has shown that B frequency increased drastically in the Mogi-Gua double dagger u river population of Prochilodus lineatus in the early 1980s, whereas it remained about constant in the 1990s. Here we analyses B frequency in this population during the 2003-2007 period and have found that frequency has not changed significantly since 1987, and that these B chromosomes do not show the intra-individual variation in number that characterized them in the 1980s. This indicates that these B chromosomes have been neutralized, after their invasion, through their mitotic stabilization.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Karyotypic conservatism in five species of Prochilodus (Characiformes, Prochilodontidae) disclosed by cytogenetic markers

The family Prochilodontidae is considered a group with well conserved chromosomes characterized by their number, morphology and banding patterns. Thence, our study aimed at accomplishing a cytogenetic analysis with conventional methods (Giemsa staining, silver staining of the nucleolus organizer regions-AgNOR, and C-banding) and fluorescence in situ hybridization (FISH) with 18S and 5S ribosomal DNA probes in five species of the Prochilodus genus (Prochilodus argenteus, Prochilodus brevis, Prochilodus costatus, Prochilodus lineatus and Prochilodus nigricans) collected from different Brazilian hydrographic basins. The results revealed conservatism in chromosome number, morphology, AgNORs 18S and 5S rDNAs location and constitutive heterochromatin distribution patterns. The minor differences observed in this work, such as an Ag-NOR on a P. argenteus chromosome and a distinct C-banding pattern in P. lineatus, are not sufficient to question the conservatism described for this group. Future work using repetitive DNA sequences as probes for FISH will be interesting to further test the cytogenetic conservatism in Prochilodus. © 2013, Sociedade Brasileira de Genética.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Chromosomal location of retrotransposable REX 1 in the genomes in five Prochilodus (Teleostei: Characiformes)

Transposable elements are repetitive DNA sequences comprising a group of segments able to move and carry sequences within the genome. Studies involving comparative genomics have revealed that most vertebrates have different populations of transposable elements with significant differences among species of the same lineage. Few studies have been conducted in fish, the most diverse group of vertebrates, with the objective to locate different types of transposable elements. Therefore, this study proposed to map the retrotransposable element Rex1 applying Fluorescent in situ Hybridization (FISH) in five species of the genus Prochilodus (Prochilodus argenteus, Prochilodus brevis, Prochilodus costatus, Prochilodus lineatus and Prochilodus nigricans). After the application of the Rex1 probe, scattered markings were found throughout the genome of analyzed species, and also the presence of small clusters located in the centromeric and telomeric regions coincident with the heterochromatin distribution pattern. This was the first description of the retrotransposable element Rex1 in Prochilodus genome seeking for a better understanding of the distribution pattern of these retrotransposons in the genome of teleost fish.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

First cytogenetic characterization of the giant Amazonian catfish Brachyplatystoma filamentosum (Siluriformes, Pimelodidae)

In contrast to the enormous variability of Neotropical fish species, genetic information about many groups is not yet available. Chromosomal studies have greatly contributed to the characterization of several species, providing important data on these animals. We performed the first cytogenetic characterization of the Amazonian fish species Brachyplatystoma filamentosum (Pimelodidae), popularly known as "piraiba". The results revealed a diploid number of 2n = 56 composed of 24 metacentric, 12 submetacentric, and 10 acrocentric chromosomes in both females and males. After silver nitrate treatment (AgNORs) it was possible to visualize the nucleolus organizer region located in the terminal portion of the short arms of subtelocentric chromosome pair 22, presenting size polymorphism. Hybridization with 18S and 5S rDNA probes confirmed the number and location of 18S marks rDNA in pair 22 and differences in the size of signals among homologs. The 5S rDNA genes were localized near the centromere on the short arms of chromosome pair 19. Constitutive heterochromatin (C-bands) were localized predominantly in the terminal regions of the chromosomes, and also occurred in some interstitial and centromeric positions. The chromosomal genetic data obtained in this study contribute to the biological characterization of B. filamentosum, which has economic and ecological importance as the largest freshwater catfish occurring in many rivers of the Amazon and Tocantins-Araguaia basins in Brazil. These results may also be used in to infer relationships among Pimelodidae species.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP