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The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large-scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications.

Farlowella is the second richest genus in Loricariinae, broadly distributed in freshwater streams and rivers of South America. In this article, we aimed to expand on the cytogenetic and molecular data available for two allopatric populations of Farlowella hahni. Both populations had diploid chromosome number 58, but with karyotype differences, indicative of chromosomal rearrangements. C-banding showed large heterochromatic blocks at telomeric regions in acrocentric chromosomes in both populations. Fluorescence in situ hybridization (FISH) revealed a single 18S rDNA site in both populations and a single 5S rDNA site for individuals from lower Parana River basin (native region) and multiple 5S rDNA sites for individuals from upper Parana River basin (non-native region). Mitochondrial sequence analyses did not separate the two F. hahni populations. The cytogenetic and molecular data obtained are relevant in a preliminary study and suggested the existence of cryptic diversity and the hypothesis that at least two Farlowella lineages may coexist in the Parana basin.

Made available in DSpace on 2020-12-12T01:13:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-02-01 Cytogenetic data showed a variation in diploid chromosome number in the genus Hyphessobrycon ranging from 2n = 46 to 52, and studies involving repetitive DNA sequences are scarce in representatives of this genus. The purpose of this paper was the chromosomal mapping of repetitive sequences (rDNA, histone genes, U snDNA and microsatellites) and investigation of the amplification of 5S rDNA clusters in the Hyphessobrycon eques genome. Two H. eques populations displayed 2n = 52 chromosomes, with the acrocentric pair No. 24 bearing Ag-NORs corresponding with CMA3+/DAPI−. FISH with a 18S rDNA probe identified the NORs on the short (p) arms of the acrocentric pairs Nos. 22 and 24. The 5S rDNA probe visualized signals on almost all chromosomes in genomes of individuals from both populations (40 signals); FISH with H3 histone probe identified two chromosome pairs, with the pericentromeric location of signals; FISH with a U2 snDNA probe identified one chromosome pair bearing signals, on the interstitial chromosomal region. The mononucleotide (A), dinucleotide (CA) and tetranucleotide (GATA) repeats were observed on the centromeric/pericentromeric and/or terminal positions of all chromosomes, while the trinucleotide (CAG) repeat showed signals on few chromosomes. Molecular analysis of 5S rDNA and non-transcribed spacers (NTS) showed microsatellites (GATA and A repeats) and a fragment of retrotransposon (SINE3/5S-Sauria) inside the sequences. This study expanded the available cytogenetic data for H. eques and demonstrated to the dispersion of the 5S rDNA sequences on almost all chromosomes. Centro de Ciências Biológicas e da Saúde Laboratório de Citogenética Universidade Estadual do Oeste do Paraná (UNIOESTE), Rua Universitária, 2069 Universidade Estadual de Mato Grosso do Sul (UEMS) Unidade de Mundo Novo, BR 163, Km 20.2 Instituto de Biociências Departamento de Biologia Laboratório de Citogenética Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Av. 24A, 1515 Instituto de Biociências Departamento de Biologia Laboratório de Citogenética Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Av. 24A, 1515

Gymnotiformes fishes present a great variation in chromosome numbers. Sternopygidae species are either sex-homomorphic or sex-heteromorphic. This study reports a novel ZZ/ZW chromosome morphology type in Eigenmannia virescens collected from the upper Parana River basin, which presented karyotype composed of 2n = 38 chromosomes, 6 metacentric (m), 10 submetacentric (sm), 4 subtelocentric (st) and 18 acrocentric (a) for males and 5 m, 11 sm, 4 st and 18 a for females, where the Z is a metacentric chromosome and the W is submetacentric chromosome. A single pair of chromosomes carrying the nucleolar organizing regions (NORs) was detected in the acrocentric chromosome pair No. 15 by silver-staining and confirmed by the 18S rDNA-FISH. Multiple 5S rDNA sites were detected in the karyotype, all of them in pericentromeric regions. The heterochromatin was mainly located in the pericentromeric regions of all chromosomes, and a conspicuous accumulation of heterochromatin colocated in NORs sites. Thus, the variation of Z and W chromosome types, associated with different chromosome sex systems (undifferentiated, XX/XY and ZZ/ZW) and different karyotypic formulae, reinforce that E. virescens should be considered a species complex.

Made available in DSpace on 2019-10-06T15:32:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-02-01 Astyanax is a genus with a wide distribution ranging from the south United States to north of Patagonia (Argentina). The available cytogenetic data on Astyanax indicate a high karyotypic diversity, with diploid number of 36-52 chromosomes, presence of B chromosomes, heterochromatin polymorphism, and variations with respect to the number and localization of nucleolar organizer regions (NORs) and 18S and 5S ribosomal DNA sites. In the present study, we estimated the evolutionary history and times of divergence for 10 nominal Astyanax species from the South and Central/North American (Cna) continents, which present distinct chromosomal characteristics, based on molecular clocks inferred from mitochondrial DNA sequence. The molecular clock results indicate the origin of three distinct clades (Humeral dark spot [Hds]; Diffuse humeral spot [Dhs]; Cna group) during the late Miocene about 11.2 million years ago (Mya). Thus, Astyanax mexicanus (Cna) represent a species that diverged a long time ago (∼8.6 Mya) from the Hds group, and Astyanax schubarti is the oldest species (∼6.5 Mya) among the Dhs species. Laboratório de Citogenética Departamento de Biologia Instituto de Biociências Universidade Estadual Paulista júlio de Mesquita Filho (UNESP), Avenue 24A Universidade Estadual de Mato Grosso Do sul (UEMS) Unidade de Mundo Novo Universidade Federal Do Rio de Janeiro (UFRJ) Núcleo em Ecologia e Desenvolvimento Socioambiental de Macaé (NUPEM/UFRJ) Laboratório de Genética Animal Departamento de Biologia e Zoologia Instituto de Biociências Universidade Federal de Mato Grosso (UFMT) Laboratório de Citogenética Departamento de Biologia Instituto de Biociências Universidade Estadual Paulista júlio de Mesquita Filho (UNESP), Avenue 24A

The W chromosome of Megaleporinus trifasciatus was isolated in order to analyze its behavior in the karyotype of this and other species of the family, including forms with differentiated and undifferentiated sex chromosomes. The chromosome was microdissected, and the WMt probe was prepared for the chromosome painting procedure. M. trifasciatus was also cross-hybridized (cross-FISH) using existing probes available for M. macrocephalus (WMm) and M. elongatus (WMe). Two Leporinus species and Semaprochilodus taeniurus, representing a clade close to the Anostomidae, were also cross-hybridized with the objective to better understand the evolution of the sex chromosomes. In the metaphase of female M. trifasciatus, the WMt probe highlighted the whole long arm of the W chromosome and a small, distal portion of the long arm of the Z chromosome. In males, the probe highlighted the distal portion of the long arm of the Z chromosomes. The hybridization of female M. trifasciatus with the WMe and WMm probes revealed a pattern similar to that encountered using the WMt probe. The WMt, WMm, and WMe probes revealed broad similarities among the species of the genus Megaleporinus, which has a ZZ/ZW system of sex chromosomes, with only minor alterations becoming apparent when analyzed separately.

Made available in DSpace on 2018-11-26T17:44:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-12-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The Piabina genus was allocated in Stervadiinae subfamily after staying for years as an uncertain group in Characidae. Few cytogenetic studies are described in the literature for Piabina argentea, thus new analyzes in other populations are important to understanding of the chromosomal dynamics of them. The aim of this paper was to analyze the chromosomes of P. argentea from Corumbatai River basin focusing mainly the chromosomal locations of 18S rDNA and 5S rDNA clusters. The diploid chromosome number was 2n = 52 for P. argentea, which were classified as 6 metacentrics (m), 8 submetacentrics (sm), 24 subtelocentrics (st) and 14 acrocentrics (a), and FN (fundamental number) value 90 in both sexes. Silver nitrate impregnation located the nucleolus organizer regions (Ag-NORs) on the short (p) arm of pair 16, however, an intra-individual variation of Ag-NORs sites was observed in two individuals. Fluorescence in situ hybridization (FISH) revealed six 18S rDNA sites (pairs 8, 10 and 16) and four 5S rDNA sites in terminal positions of the short arm of pairs 5 and 22 (one submetacentric and one acrocentric) in P. argentea. The results indicate that, despite the conserved diploid number, this group of fish presents a wide variability of the 18S and 5S rDNA sites. Univ Estadual Paulista, UNESP, Inst Biociencias, Dept Biol,Lab Citogenet, Av 24A,1515, BR-13506900 Rio Claro, SP, Brazil Univ Estadual Mato Grosso do Sul UEMS, Unidade Mundo Novo, BR 163,Km 20-2, BR-79980000 Mundo Novo, MS, Brazil Univ Estadual Paulista, UNESP, Inst Biociencias, Dept Biol,Lab Citogenet, Av 24A,1515, BR-13506900 Rio Claro, SP, Brazil

Gymnorhamphichthys britskii is a Neotropical electric fish of family Rhamphichthyidae described from the Paraná-Paraguay system. This study reports the first karyotypic description of G. britskii collected from the upper Paraná river basin, which presented 2n=38 chromosomes, karyotype composed of 14 metacentric, 8 submetacentric, 2 subtelocentric and 14 acrocentric chromosomes, and fundamental number as 62 for both sexes. Heteromorphic sex chromosomes were absent. A single pair of nucleolar organizing regions (NORs) was detected in the submetacentric chromosome pair number 9 by silver staining and confirmed by the 18S rDNA probe. The 5S rDNA was located in a single chromosome pair. Heterochromatic regions were clearly observed in the short arms of the NOR-bearing chromosome pair and in the telomeric positions of most acrocentric chromosomes. Besides the present data are valuable to help in understanding karyotypic evolution in Rhamphichthyidae, data from NORs confirmed the tendency of this family in presenting simple NORs sites, similar to the other Gymnotiformes clades. Yet, the presence of a large heterochromatic block in the NOR-bearing chromosome can be used as cytogenetic markers for G. britskii, and that centric fusions appear to be an important mechanism in the karyotype evolution and differentiation among Gymnotiformes species. RESUMO Gymnorhamphichthys britskii é um peixe neotropical da família Rhamphichthyidae descrita no sistema Paraná-Paraguai. Este estudo relata a primeira descrição cariotípica de G. britskii coletado na bacia do alto rio Paraná, que apresentou 2n = 38 cromossomos, cariótipo composto por 14 metacêntricos, 8 submetacêntricos, 2 subtelocêntricos e 14 acrocêntricos, e número fundamental 62 para ambos sexos. Cromossomos sexuais heteromórficos estavam ausentes. Um único par de regiões organizadoras de nucléolos (RONs) foi detectado no par de cromossomos submetacêntricos número 9 por coloração com prata e confirmado pela sonda DNAr 18S. O DNAr 5S foi localizado em um único par cromossômico. Regiões heterocromáticas foram claramente observadas nos braços curtos do par de cromossomos que carrega a RON e nas posições teloméricas da maioria dos cromossomos acrocêntricos. Além dos dados presentes serem valiosos para auxiliar na compreensão da evolução cariotípica em Rhamphichthyidae, dados de RONs confirmaram a tendência desta família em apresentar sítios simples de RONs, semelhantes aos demais clados de Gymnotiformes. No entanto, a presença de um grande bloco heterocromático no cromossomo portador da RON, pode ser usado como marcador citogenético para G. britskii e as fusões cêntricas parecem ser um mecanismo importante na evolução e diferenciação cariotípica entre as espécies de Gymnotiformes.

Made available in DSpace on 2018-12-11T16:47:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-01 Repetitive sequences and their chromosomal locations have been widely studied in species of the Astyanax genus. However, the chromosomal organization of U2 snDNA remains largely unknown. The aims of this study were to examine the chromosomal contexts of U2 snRNA and 5S rRNA genes in Astyanax species and determine the degree of chromosome morphological similarity between species with different diploid numbers. Clusters of U2 snDNA and 5S rDNA were determined in nine species of Astyanax, including two karyomorphs of Astyanax fasciatus Cuvier, 1819. All species exhibited U2 snDNA clusters on two chromosome pairs, except Astyanax mexicanus De Filippi, 1853 (one pair). The 5S rDNA clusters were located on one chromosome pair in Astyanax altiparanae Garutti and Britski, 2000, and Astyanax marionae Eigenmann, 1911, two pairs in Astyanax abramis Jenyns, 1842, Astyanax asuncionensis Géry, 1972, Astyanax bockmanni Vari and Castro, 2007, Astyanax eigenmanniorum Cope, 1894, A. fasciatus (karyomorphs I and II), and Astyanax schubarti Britski, 1964, and four pairs in A. mexicanus. The relationships between the repetitive sequences in different species suggest that A. schubarti and A. mexicanus exhibit an unusual U2 snDNA chromosomal format as a result of events occurring in the evolutionary history of the Astyanax group. Laboratório de Citogenética Departamento de Biologia Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Av. 24A, 1515 Laboratório de Genética Animal Departamento de Biologia e Zoologia, Universidade Federal de Mato Grosso (UFMT) Laboratório de Citogenética Departamento de Biologia Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Av. 24A, 1515

Made available in DSpace on 2018-12-11T16:41:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-01-17 The genus Astyanax is widely distributed from the southern United States to northern Patagonia, Argentina. While cytogenetic studies have been performed for this genus, little is known about the histone gene families. The aim of this study was to examine the chromosomal relationships among the different species of Astyanax. The chromosomal locations of the 5S rRNA and H3 histone genes were determined in A. abramis, A. asuncionensis, A. altiparanae, A. bockmanni, A. eigenmanniorum, A. mexicanus (all 2n = 50), A. fasciatus (2n = 46), and A. schubarti (2n = 36). All eight species exhibited H3 histone clusters on two chromosome pairs. In six species (A. abramis, A. asuncionensis, A. altiparanae, A. bockmanni, A. eigenmanniorum, and A. fasciatus), syntenic clusters of H3 histone and 5S rDNA were observed on metacentric (m) or submetacentric (sm) chromosomes. In seven species, clusters of 5S rDNA sequences were located on one or two chromosome pairs. In A. mexicanus, 5S rDNA clusters were located on four chromosome pairs. This study demonstrates that H3 histone clusters are conserved on two chromosome pairs in the genus Astyanax, and specific chromosomal features may contribute to the genomic organization of the H3 histone and 5S rRNA genes. Instituto de Biociências Departamento de Biologia Laboratório de Citogenética Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Av. 24A, 1515 Instituto de Biociências Departamento de Biologia Laboratório de Citogenética Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Av. 24A, 1515

The organization of microsatellites in B and sex chromosomes has been linked to chromosomal evolution in a number of animal groups. Here, the chromosomal organizations of (CA)15, (GA)15, (CG)15, (GACA)4, and (GATA)8 microsatellites were examined in several Astyanax species with different diploid numbers: Astyanax mexicanus (2n = 50 + 1 B chromosome), A. altiparanae (2n = 50), A. marionae (2n = 48), A. fasciatus (2n = 46), and A. schubarti (2n = 36). The (CA)15 and (GA)15 microsatellites were dispersed across the chromosomes of A. altiparanae and A. fasciatus but were also observed as clusters (CA and GA for A. altiparanae, and CA for A. fasciatus). In A. marionae and A. schubarti, the (CA)15 and (GA)15 microsatellites were dispersed but were also observed as clustered signals and coincident with heterochromatic regions. In all 4 of these species, the (CG)15 and (GACA)4 microsatellites were dispersed across chromosomes, and the (GATA)8 microsatellite was co-localized with 5S rDNA. In A. mexicanus, the (CA)15, (GA)15, (CG)15, (GATA)8, and (GACA)4 microsatellites were weakly detected and dispersed across the chromosomes of the A complement. On the B chromosome, signals for the different microsatellites were weak, strong, absent, weak, and absent, respectively. The distribution of microsatellites and the locational relationship between microsatellites and 5S rDNA are discussed, and a possible evolutionary pathway is proposed for microsatellites in Astyanax.

Made available in DSpace on 2018-12-11T16:52:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The U small nuclear RNA (U snRNA) genes comprise a multigene family and are required for splicing of pre-mRNA. In this paper, we aimed to study the chromosomal location of the U2 snRNA gene in Megaleporinus, Leporinus and Schizodon species, which constitute interesting models for the study of repetitive DNA and genomic evolution in fish once the group comprises species with and without heteromorphic sex chromosomes. The all six species showed 2n = 54 chromosomes: Megaleporinus elongatus, Megaleporinus macrocephalus, Leporinus striatus, Leporinus friderici, Schizodon borelli and Schizodon isognathus. The U2 snDNA clusters were evident in only one medium-sized submetracentric pair in all analyzed species and this may represent a condition shared by Anostomidae family. Instituto de Biociências Departamento de Biologia Laboratório de Citogenética Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Av. 24A, 1515 Instituto de Biociências Departamento de Biologia Laboratório de Citogenética Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Av. 24A, 1515 FAPESP: 10/10/51339-0

The W chromosome of Megaleporinus trifasciatus was isolated in order to analyze its behavior in the karyotype of this and other species of the family, including forms with differentiated and undifferentiated sex chromosomes. The chromosome was microdissected, and the WMt probe was prepared for the chromosome painting procedure. M. trifasciatus was also cross-hybridized (cross-FISH) using existing probes available for M. macrocephalus (WMm) and M. elongatus (WMe). Two Leporinus species and Semaprochilodus taeniurus, representing a clade close to the Anostomidae, were also cross-hybridized with the objective to better understand the evolution of the sex chromosomes. In the metaphase of female M. trifasciatus, the WMt probe highlighted the whole long arm of the W chromosome and a small, distal portion of the long arm of the Z chromosome. In males, the probe highlighted the distal portion of the long arm of the Z chromosomes. The hybridization of female M. trifasciatus with the WMe and WMm probes revealed a pattern similar to that encountered using the WMt probe. The WMt, WMm, and WMe probes revealed broad similarities among the species of the genus Megaleporinus, which has a ZZ/ZW system of sex chromosomes, with only minor alterations becoming apparent when analyzed separately.

Made available in DSpace on 2018-12-11T16:51:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-02 The cytogenetic studies of retrotranposons Rex have been characterized in several fish groups, including species of the Astyanax genus. This group presents an extensive variability in their karyotype, with diploid numbers of 2n = 52, 50, 48, 46 and 36 chromosomes. Thus, the aim of this study was to evaluate the distribution of the retrotransposable element Rex1, in six Astyanax species, with different diploid numbers. The species analyzed were Astyanax altiparanae (2n = 50), Astyanax asuncionensis (2n = 50), Astyanax eigenmanniorum (2n = 50), Astyanax marionae (2n = 48), Astyanax fasciatus (2n = 46) and Astyanax schubarti (2n = 36). Rex1 was dispersed in the Astyanax species, suggesting that these retrotransposons play important role in genome evolution. Instituto de Biociências Departamento de Biologia Laboratório de Citogenética Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP) Instituto de Biociências Departamento de Biologia e Zoologia Laboratório de Genética Animal Universidade Federal de Mato Grosso (UFMT) Instituto Federal de Educação Ciência e Tecnologia do Piauí (IFPI) Laboratório de Biologia Instituto de Biociências Departamento de Biologia Laboratório de Citogenética Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP)

Made available in DSpace on 2015-10-21T13:12:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-02-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The species of genus Astyanax is widely distributed in freshwater neotropical zones. Astyanax is considered to be taxonomically confused, similar to other genera placed incertae sedis in Characidae. The cytogenetics of this genus is well characterized; species vary widely in diploid number, from 2n=36 chromosomes in Astyanax schubarti to 2n=50 for most species studied. The size, number, and position of different cytological markers vary among species and populations of Astyanax. We analyzed the karyotypes of individuals from three Astyanax species (Astyanax abramis, Astyanax altiparanae, and Astyanax eigenmanniorum) from populations not previously analyzed. We describe variations in several cytogenetic markers and the karyotypic relationships between them, specifically focusing on the characteristics of the conserved and divergent locations of the ribosomal genes. Our data are useful for establishing relationships between species and for investigating the karyotype evolution within the genus. Universidade Estadual Paulista ‘‘Júlio de Mesquita Filho’’ (UNESP) - Laboratório de Citogenética, Departamento de Biologia, Instituto de Biociências, Rio Claro, São Paulo, Brasil. Empresa Brasileira de Pesquisa Agropecuária (Embrapa) Pesca e Aquicultura (CNPASA), Palmas, Tocantins, Brasil Universidade Estadual Paulista ‘‘Júlio de Mesquita Filho’’ (UNESP) - Laboratório de Citogenética, Departamento de Biologia, Instituto de Biociências, Rio Claro, São Paulo, Brasil.

The organization of microsatellites in B and sex chromosomes has been linked to chromosomal evolution in a number of animal groups. Here, the chromosomal organizations of (CA)15, (GA)15, (CG)15, (GACA)4, and (GATA)8 microsatellites were examined in several Astyanax species with different diploid numbers: Astyanax mexicanus (2n = 50 + 1 B chromosome), A. altiparanae (2n = 50), A. marionae (2n = 48), A. fasciatus (2n = 46), and A. schubarti (2n = 36). The (CA)15 and (GA)15 microsatellites were dispersed across the chromosomes of A. altiparanae and A. fasciatus but were also observed as clusters (CA and GA for A. altiparanae, and CA for A. fasciatus). In A. marionae and A. schubarti, the (CA)15 and (GA)15 microsatellites were dispersed but were also observed as clustered signals and coincident with heterochromatic regions. In all 4 of these species, the (CG)15 and (GACA)4 microsatellites were dispersed across chromosomes, and the (GATA)8 microsatellite was co-localized with 5S rDNA. In A. mexicanus, the (CA)15, (GA)15, (CG)15, (GATA)8, and (GACA)4 microsatellites were weakly detected and dispersed across the chromosomes of the A complement. On the B chromosome, signals for the different microsatellites were weak, strong, absent, weak, and absent, respectively. The distribution of microsatellites and the locational relationship between microsatellites and 5S rDNA are discussed, and a possible evolutionary pathway is proposed for microsatellites in Astyanax.

The genus Piabucus is the only member of the subfamily Iguanodectinae found in the Pantanal of Mato Grosso State, where it is represented by Piabucus melanostomus. P. melanostomus from the Paraguay and Bento Gomes Rivers of the Pantanal wetlands were analysed using conventional and molecular cytogenetic techniques to cytogenetically characterise the species and broaden the knowledge of the subfamily. The results indicated no sex-related heteromorphisms. The diploid number for the species was 2n = 50 chromosomes, which were divided into six metacentric, eight submetacentric, 24 subtelocentric, and 12 acrocentric with a fundamental number (FN) of 88. Heterochromatin was visualised using the C-banding technique, which showed that it was mainly distributed in the centromeric and pericentromeric region of most chromosomes, but larger blocks were observed on the long arms of large subtelocentric chromosomes (8, 9, 10, 13, and 20 pairs). Nucleolar organising regions (Ag-NOR) were observed in the p-subterminal region of one subtelocentric chromosome pair (9) with a remarkable size polymorphism between homologues in individuals from the Paraguay River, which was confirmed using the FISH technique with 18S rDNA. In this population, in all individuals studied, one of the homologous shows block considerably larger. The karyotype was compared with those of other subfamilies considered basal in Characidae, according to morphological data.

Characidae is one of the predominant fish groups in the Neotropical region with approximately 30 highly diversified subfamilies, probably not representing a monophyletic group. Three Characidae species from the Iguatemi River Basin (Mundo Novo, MS, Brazil) were analyzed: Astyanax bockmanni with 2n=50 chromosomes (6m+20sm+8st+16a), Bryconamericus stramineus with 2n=52 chromosomes (6m+10sm+16st+20a) and Piabina argentea with 2n=52 chromosomes (6m+24sm+12st+10a), all the species showing no differences between male and female karyotypes. The Ag-NORs were located in only a single chromosome pair in the three species. The chromosomal data obtained may be useful for the taxonomy and phylogenetic studies in these fish groups.

Made available in DSpace on 2014-12-03T13:11:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-04-01Bitstream added on 2014-12-03T13:22:50Z : No. of bitstreams: 1 WOS000317829800001.pdf: 597255 bytes, checksum: d596e504ddd65c823178cb74e22b9092 (MD5) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Background: Nowadays, the genus Bryconamericus is placed in subfamily Stevardiinae within of Characidae, but not shows consistent evidence of monophyletism. The purpose of this work was to study the chromosomes of three species of Bryconamericus, aiming to add cytogenetic knowledge and contribute to the understanding of the chromosomal evolution of this genus.Results: The chromosomes of three species of Bryconamericus were analyzed using cytogenetic techniques. The karyotype of Bryconamericus stramineus contained 6 metacentric (m) + 10 submetacentric (sm) + 16 subtelocentric (st) + 20 acrocentric (a), the fundamental number (FN) of 84, one silver impregnated (Ag-NOR) pair, one pair bearing the 18S ribosomal DNA sites, another pair bearing the 5S rDNA sites, and a few positive C-bands. Bryconamericus turiuba had a karyotype containing 8 m + 10sm + 14st + 20a (FN = 84), one chromosome pair Ag-NOR, two pairs bearing the 18S rDNA sites, two pairs bearing the 5S rDNA sites, and a few C-band regions. Bryconamericus cf. iheringii had a karyotype containing 10 m + 14sm + 18st + 10a (FN = 94), including one pair with a secondary constriction Ag-NOR positive. In this karyotype the fluorescent in situ hybridization (FISH) showed the 18S and 5S rDNA probe in adjacent position.Conclusions: The results obtained in this work showed different characteristics in the organization of two multigene families, indicating that distinct evolutionary forces acting on the diversity of rDNA sequences in the genome of three Bryconamericus species. Univ Estadual Paulista Julio Mesquita Filho UNESP, Inst Biociencias, Dept Biol, Lab Citogenet, BR-13506900 Rio Claro, SP, Brazil Univ Estadual Mato Grosso Sul UEMS, BR-79980000 Mundo Novo, MS, Brazil Univ Estadual Paulista Julio Mesquita Filho UNESP, Inst Biociencias, Dept Biol, Lab Citogenet, BR-13506900 Rio Claro, SP, Brazil