Chromosome Painting in "Catalão" (Gymnotiformes, Teleostei): Dynamics of Chromosomal Rearrangements in Cryptic Species.

The genus is a large monophyletic group of freshwater weakly-electric fishes, with wide distribution in Central and South America. It has 46 valid species divided into six subgenera (, , , , and ) with large chromosome plasticity and diploid numbers (2n) ranging from 34 to 54. Within this rich diversity, there is controversy about whether () species is a single widespread species or a complex of cryptic species.

Silencing of Transposable Elements Mediated by 5-mC and Compensation of the Heterochromatin Content by Presence of B Chromosomes in .

The way in which transcriptional activity overcomes the physical DNA structure and gene regulation mechanisms involves complex processes that are not yet fully understood. Modifications in the cytosine-guanine sequence of DNA by 5-mC are preferentially located in heterochromatic regions and are related to gene silencing. Herein, we investigate evidence of epigenetic regulation related to the B chromosome model and transposable elements in .

A New Variant B Chromosome in Auchenipteridae: The Role of (GATA)n and (TTAGGG)n Sequences in Understanding the Evolution of Supernumeraries in Trachelyopterus.

Basic and molecular cytogenetic techniques were carried out in 3 Neotropical region populations of catfishes, two of Trachelyopterus galeatus (one from the marshlands of Paraguay River basin and another from Lago Catalão, Amazon River basin) and one of Trachelyopterus porosus, a sympatric population to T. galeatus from the Amazon River basin. This study aimed to describe and understand the structure and evolution of Trachelyopterus B chromosomes, mainly through physical mapping of repetitive elements.

Dynamics of Replication and Nuclear Localization of the B Chromosome in Kidney Tissue Cells in (Teleostei: Characidae).

B chromosomes are extra genomic compounds found in different taxonomic groups, including plants and animals. Obtaining patterns of resolutive chromosomal bands is necessary to understand the nuclear organization, variability and nature of B chromosome chromatin and possible transcriptional regions. In this study, we analyzed 35 specimens sampled from Fazenda Lavrinha, a stream in the Paraíba do Sul river basin, Brazil.

Karyotypic Diversity and Evolutionary Trends in Neotropical Electric Fish of the Genus (Gymnotiformes: Gymnotidae).

Electric fish of the order Gymnotiformes are endemic to the Neotropical region, and their highest diversity is observed in the Amazon region. The family Gymnotidae, which consists of the genera and , is a natural group and is located at the base of the phylogeny of the order. is a widely distributed and specious genus with high karyotypic diversity, especially concerning to the diploid number and the locations of repetitive sequences.

Variability and evolutionary implications of repetitive DNA dynamics in genome of (Teleostei, Characidae).

DNA sequences of multiple copies help in understanding evolutionary mechanisms, genomic structures and karyotype differentiation. The current study investigates the organization and distribution of different repetitive DNA in the standard complement and B chromosomes in (Jenyns, 1842) chromosomes from three allopatric populations in Campos do Jordão region, São Paulo State, Brazil. The location of microsatellite sequences showed different chromosome distribution between Lavrinha Farm Stream (LFS) and Lake of Pedalinho (LP) populations.

Evolutionary Dynamics of 5S rDNA and Recurrent Association of Transposable Elements in Electric Fish of the Family Gymnotidae (Gymnotiformes): The Case of Gymnotus mamiraua.

Gymnotidae is a family of electric fish endemic to the Neotropics consisting of 2 genera: Electrophorus and Gymnotus. The genus Gymnotus is widely distributed and is found in all of the major Brazilian river systems. Physical and molecular mapping data for the ribosomal DNA (rDNA) in this genus are still scarce, with its chromosomal location known in only 11 species.

Cytogenetic Diversity and the Evolutionary Dynamics of rDNA Genes and Telomeric Sequences in the Ancistrus Genus (Loricariidae: Ancistrini).

The Ancistrus genus differs from other Ancistrini due to its wide karyotypic diversity, varied diploid numbers, differences in sex chromosomes, and large number of species, as well as its tendency to form small populations with low vagility. This study investigated the role of 5S and 18S rDNA and telomeric repetitive sequences in the evolution of the karyotypic macrostructure of seven species of the genus Ancistrus from the Central Amazon. The results indicate a strong correlation between the location of ribosomal sites and fragile sites in the genome, particularly of 5S rDNA sequences, which are associated, in some species, with telomeric sequences at the sites of chromosomal healing.

New approach data in electric fish (Teleostei: Gymnotus): sex chromosome evolution and repetitive DNA.

Antagonist sexual selection is the driving force behind the origin and diversification of sex chromosomes such as XX/XY and ZZ/ZW. However, chromosome mobility, mainly in fishes, may result in the formation of chromosomes of recent origin, a process known as turnover. The family Gymnotidae, which is composed of the genera Electrophorus+Gymnotus, presents a multiple system of the type X1X1X2X2/X1X2Y, which has been described for Gymnotus pantanal.

Chromosomal polymorphism in two species of Hypancistrus (Siluriformes: Loricariidae): an integrative approach for understanding their biodiversity.

Structural chromosome changes are widely described in different vertebrate groups and generate genetic, phenotypic and behavioral diversity. During the evolution of loricariids, several rearrangements (fissions, fusions, inversions) seem to have occurred. Hypancistrus, tribe Ancistrini, are highly demanded for fishkeeping around the world.