Supernumerary chromosomes in the pufferfish Sphoeroides spengleri: first occurrence in marine Teleostean Tetraodontiformes fish

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Unusual occurrence of a ZZ/ZW sex-chromosome system and supernumerary chromosomes in Characidium cf. fasciatum (Pisces, Characiformes, Characidiinae)

Individuals of two populations of the fish Characidium cf. fasciatum were cytogenetically studied and showed a basic diploid number of 50 chromosomes. Some fishes were found to have 51 to 54 chromosomes due to the presence of one to four small subtelocentric/acrocentric supernumerary chromosomes. When analyzed by conventional Giemsa staining, male and female specimens of C. cf. fasciatum from the Quinta stream and Pardo River presented the same basic karyotypic macro- and microstructure, consisting of 32 metacentric and 18 submetacentric chromosomes.Ag-NORs were terminally located on the long arms of two submetacentric chromosome pairs. Constitutive heterochromatin was identified by C-banding as small pericentromeric blocks in the majority of the chromosomes, and B-chromosomes were found to be heterochromatic. The occurrence of one totally heterochromatic submetacentric chromosome restricted to females and considered as an unusual feature in fish karyotypes led to the identification of a ZZ/ZW sex-chromosome system. The implications of chromosomic differentiation observed in the genus Characidium are discussed.

Origin and molecular organization of supernumerary chromosomes of Prochilodus lineatus (Characiformes, Prochilodontidae) obtained by DNA probes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Karyotypic evolution trends in Rhamdia quelen (Siluriformes, Heptapteridae) with considerations about the origin and differentiation of its supernumerary chromosomes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synapsis in supernumerary chromosomes of Prochilodus lineatus (Teleostei: Prochilodontidae)

Meiotic analysis performed on a sample of 10 specimens of Prochilodus lineatus revealed continuous filaments of different sizes stained by AgNO3, corresponding to the bivalent of the normal complement. Small supernumerary chromosomes were observed as isolated and well stained bodies, scattered among the other elements. Synaptonemal complex studies have shown that the beginning of chromosome pairing process in P. lineatus usually occurs from the telomeres to the pericentromeric region. At the end of the pachytene 27 bivalents are perfectly paired and the small supernumerary chromosomes of this species are seen as bivalents, trivalents, or tetravalents. The central region of these small chromosomes show a trick staining when they formed bivalents or tetravalents. This portion seems to correspond to the pericentromeric region of the regular chromosomes with the heterochromatic characteristic of B chromosomes.

Identification and description of distinct B chromosomes in Cyphocharax modestus (Characiformes, Curimatidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genetics of neotropical fish: from chromosomes to populations

The Neotropical freshwater fish fauna is very rich-according to the most recent catalogue 71 families and 4,475 species have been described. However, only a small amount of general information is available on the composition of Neotropical marine fishes. In Brazil, 1,298 marine species have been recorded. General analysis of available cytogenetic and population genetic data clearly indicates research has been mainly concentrated on freshwater fishes. Thus, today, cytogenetic information is available for 475 species of Characiformes, 318 species of Siluriformes, 48 species of Gymnotiformes, 199 freshwater species that do not belong to the superorder Ostariophysi, and only 109 species of marine fishes. For the species studied, only about 6% have sex chromosomes and about 5% have supernumerary or B chromosomes. A review of the cytogenetic studies shows that these data have provided valuable information about the relationships between fish groups, the occurrence of cryptic species and species complexes, the mechanism of sex determination and sex chromosome evolution, the distribution of nucleolus organizer regions, the existence supernumerary chromosomes, and the relationship between polyploidy and evolution. In relation to populations in Neotropical marine waters, the studies have shown the presence of cryptic species, which has important implications for fishery management. Different levels of genetic structuring can be found among Neotropical freshwater migratory fish species. This raises important implications for fish population genetic diversity and consequently its sustainable utilization in inland fisheries and aquaculture, specifically for conservation of ichthyo-diversity and survival.

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

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Natural triploidy and B chromosomes in Astyanax scabripinnis (Characiformes, Characidae): a new occurrence

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The B chromosomes of the African cichlid fish Haplochromis obliquidens harbour 18S rRNA gene copies

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Supernumerary chromosome inheritance in the curimbata (Prochilodus lineatus) of the Mogi-Guacu River

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetic analysis of B chromosomes in one population of the fish Moenkhausia sanctaefilomenae (Steindachner, 1907) (Teleostei, Characiformes)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Molecular characterization and chromosomal localization of two families of satellite DNA in Prochilodus lineatus (Pisces, Prochilodontidae), a species with B chromosomes

Prochilodus lineatus, an abundant species in the Mogi-Guaçu river basin, represents a large part of the region's fishing potential. Karyotypic analyses based on classic cytogenetic techniques have revealed the presence of 54 metasubmetacentric type chromosomes, together with the occurrence of small supernumerary chromosomes with intra and interindividual variations. This paper describes the genomic organization of two families of satellite DNA in the P. lineatus genome. The chromosomal localization these two repetitive DNA families through fluorescence in situ hybridization (FISH) demonstrated that the SATH1 satellite DNA family, composed of approximately 900 bp, was located in the pericentromeric region of a group of chromosomes of the standard complement, as well as on all the B chromosomes. The SATH2 satellite family has a monomeric unit of 441 bp and was located in the pericentromeric regions of some chromosomes of the standard complement, but was absent in the B chromosomes. Double FISH analyses showed that these two families participate jointly in the pericentromeric organization of several chromosomes of this species. The data obtained in this study support the hypothesis that the B chromosomes derive from chromosomes of the standard complement, which are carriers of the SATH1 satellite DNA.