Abstract The transposable elements are known by their ability to move and integrate into the genome of the host organism. They are classified in retrotransposons class I, which has, as intermediate of the transposition, the RNA and retrotransposons class II, which is composed of the DNA transposons, whose DNA migrates directly or is copied and inserted into the genome. The retrotransposable element Rex1 is a non-LTR retrotransposon found in several types of organisms. Many studies indicate that the Rex retrotransposons have the capacity to respond to environmental stress. The results found in this study corroborate the hypothesis that this retrotransposon possesses a response to environmental stress, since the chromosomal mapping, obtained through FISH, showed a higher number of markings on animals that were submitted to stress in 48h by the copper sulfate action. Furthermore, we can identify an increase in heterochromatic regions in the chromosomes. In the absolute quantification by Real-Time PCR, we found the largest numbers of Rex1 copies in the samples that were submitted to environmental stress by copper sulfate.

Abstract Austrodiplostomum Szidat & Nani, 1951 is a genus of parasitic digenetic trematodes widely distributed in the Neotropical region. Infects a wide variety of species, families and requests for freshwater fish. We identify samples of Austrodiplostomum sp, based on metacercariae isolates from eyes of tambaqui (Colossoma macropomum), a fish of high commercial importance in Brazil, and widely consumed by the population of the northern region. The sequences obtained clustered with A. compactum. This is the first report of the occurrence of diplostomids in farmed tambaqui in Amazonia.

The Serrasalmidae family is composed of a number of commercially interesting species, mainly in the Amazon region where most of these fishes occur. In the present study, we investigated the genomic organization of the 18S and 5S rDNA and telomeric sequences in mitotic chromosomes of four species from the basal clade of the Serrasalmidae family: Colossoma macropomum, Mylossoma aureum, M. duriventre, and Piaractus mesopotamicus, in order to understand the chromosomal evolution in the family. All the species studied had diploid numbers 2n = 54 and exclusively biarmed chromosomes, but variations of the karyotypic formulas were observed. C-banding resulted in similar patterns among the analyzed species, with heterochromatic blocks mainly present in centromeric regions. The 18S rDNA mapping of C. macropomum and P. mesopotamicus revealed multiple sites of this gene; 5S rDNA sites were detected in two chromosome pairs in all species, although not all of them were homeologs. Hybridization with a telomeric probe revealed signals in the terminal portions of chromosomes in all the species and an interstitial signal was observed in one pair of C. macropomum.

Dados cariotípicos são apresentados para quatro espécies da família Pimelodidae. Todas apresentaram o mesmo número diploide, 2n = 56 cromossomos, com diferenças nas fórmulas cariotípicas. As espécies aqui analisadas mostraram pouca quantidade de heterocromatina localizada preferencialmente na região centromérica e telomérica de alguns cromossosmos do complemento cariotípico. As regiões organizadoras de nucléolo (Ag-RONs) e a localização dos genes ribossomais pela hibridização in situ fluorescente (FISH), com sondas 18S e 5S, evidenciaram somente um par cromossômico marcado portador de genes ribossomais, à exceção de Pimelodus britskii que apresentou NORs múltiplas e localização sintênica das sondas 18S e 5S. Eventos não-Robertsonianos, como inversão pericêntrica e duplicação das NORs são requeridos para explicar a diversificação cariotípica em Pseudoplatystoma do rio Paraguai (MS), Pimelodus do rio Iguaçu (PR), Sorubim do rio Paraguai (MS) e Steindachneridion do rio Paraíba do Sul (SP). Os dados obtidos para a macroestrutura cariotípica destas espécies corrobora um padrão conservado observado na família Pimelodidae. Por outro lado, evidências de variações interespecíficas pelos marcadores de citogenética molecular empregados possibilitam inferências citotaxonômicas e diferenciação das espécies aqui analisadas.

Karyotypic data are presented for four species of fish belonging to the Pimelodidae family. These species show a conserved diploid number, 2n = 56 chromosomes, with different karyotypic formulae. The analyzed species showed little amount of heterochromatin located preferentially in the centromeric and telomeric regions of some chromosomes. The nucleolus organizer regions activity (Ag-NORs) and the chromosomal location of ribosomal genes by fluorescent in situ hybridization (FISH), with 18S and 5S probes, showing only one chromosome pair marked bearer of ribosomal genes, the only exception was Pimelodus britskii that presented multiple NORs and syntenic location of the 18S and 5S probes. Non-Robertsonian events, as pericentric inversion and NORs duplication are requested to explain the karyotype diversification in Pseudoplatystoma from the rio Paraguay (MS), Pimelodus from the rio Iguaçu (PR), Sorubim from the rio Paraguay (MS) and Steindachneridion from the rio Paraíba do Sul (SP). The obtained data for the karyotype macrostructure of these species corroborates a conserved pattern observed in Pimelodidae. On the other hand, interspecific variations detected by molecular cytogenetics markers made possible cytotaxonomic inferences and differentiation of the species here analyzed.

Uma análise qualitativa da variabilidade genética em Astyanax fasciatus (Cuvier, 1819) do alto Rio Tibagi e Parque Estadual de Vila Velha (PEVV) foi conduzida por digestão enzimática (RFLP) da região D-Loop do mtDNA. Os resultados evidenciaram que essas populações são geneticamente diferentes.

A preliminary qualitative analysis of genetic variability status in Astyanax fasciatus (Cuvier, 1819) from upper Tibagi River headwaters and Vila Velha State Park (VVSP) was carried out by enzymatic digestion (RFLP) of D-Loop region from mtDNA. The results showed that Tibagi and VVSP populations were genetically different.