Contributions to the cytogenetics of the Neotropical fish fauna.

Brazilian fish cytogenetics started as early as the seventies in three pioneering research groups, located at the Universidade Estadual Paulista (UNESP, Botucatu, SP), Universidade Federal de São Carlos (UFSCar, São Carlos, SP) and Universidade de São Paulo (USP, São Paulo, SP). Investigations that have been conducted in these groups led to the discovery of a huge chromosomal and genomic biodiversity among Neotropical fishes. Besides, they also provided the expansion of this research area, with the genesis of several other South American research groups, in view of a number of dissertations and doctoral theses developed over years. The current authors were encouraged to make their thesis catalog accessible from a public source, in order to share informations on the taxa and subject matter analyzed. Some of the key contributions to evolutionary fish cytogenetics are also being highligthed.

Introduction

About 13,000 freshwater fish species are now recognized, 50% of them living in the Neotropical region (Reis et al. 2003), which emphasizes the significant parcel of the ichthyological diversity enclosed in this particular world region. Of course, this was one of the main reasons that attracted the attention of some Brazilian researchers, fostering the investigation on cytogenetics of Neotropical fishes.

Brazilian fish cytogenetics started in the early 70s, with three pioneering research groups located at the Universidade Estadual Paulista (UNESP, Botucatu, SP), Universidade Federal de São Carlos (UFSCar, São Carlos, SP) and Universidade de São Paulo (USP, São Paulo, SP). During this time, a lot of significant evolutionary and cytotaxonomic contributions were achieved, improving the knowledge on the biodiversity inside the rich Neotropical ichthyofauna.

The development of methodological approaches was certainly a key step for obtaining good chromosomal preparations and for improving fish cytogenetics. In this sense, the direct chromosome preparation from kidney cells, adapted in our early studies since 70s and recently revised (Bertollo et al. 2015), was largely utilized over years. In addition, the progressive application of conventional banding techniques (C, AgNORs, DAPI, CMA3 staining), as well as more advanced methodologies combining cytogenetic and molecular procedures (chromosome mapping of DNA sequences by FISH, whole chromosome painting – WCP and comparative genomic hybridization – CGH) were essential tools in understanding the fish genome organization, particularly regarding to sex chromosome evolution and biodiversity investigations.

Although primarily and mainly devoted to freshwater species, the chromosomal analyses were also expanded to marine fishes, which is now the particular focus of some laboratories. From 1986 to now, successful biennual symposiums on fish cytogenetics are ongoing at different Brazilian regions. From some years ago, the discipline of genetics was also added to such meetings, with an expressive participation of professionals, students, as well as foreign invited researchers.

The catalogue of student theses, supervised in the Laboratory of Fish Cytogenetics of the Universidade Federal de São Carlos, comprises 42 doctoral theses and 52 master dissertations from 1981 to 2016. Informations about their corresponding students, taxa and matter subjects are available in the present communication, considering that not all the resulting data have been published. Theses/dissertations produced were assembled by taxonomic groups, according to Reis et al. (2003), regardless of their chronology. This criterion provides an overview of the different studied groups, considering that several families, genera and species have wider distribution and were subjected of more extensive investigations, being analyzed by different authors. The "taxa analyzed" item makes explicit when different populations, as well as different karyomorphs (karyotypes with distinct characteristics from each other) of a given species were investigated. The term “species group” was used for cases of specimens showing morphological similarities to a given valid species, but missing a proper taxonomic revision by the time they were studied.

Significantly, more than 20 research groups, nowadays located in different Brazilian regions, and also in Argentina, have emerged from such studies. These new researchers, along with those that have been emerged from the other pioneer laboratories, are now also engaged on fish chromosomal investigations. This was a preponderant condition for the big expansion experienced by the Brazilian fish cytogenetics.

The "Final Remarks" highlights some key contributions to fish evolutionary cytogenetics from MSc and PhD theses produced, as well as from other results that were led by our research team, some of them with significant colaborations of other national and international research groups.

Laboratory site at the Universidade Federal de São Carlos: (http://www.lcp.ufscar.br)

Abbreviations used

Universidade Federal de São Carlos

Instituto Nacional de Pesquisas da Amazônia

Universidade de São Paulo

Universidade Federal do Rio de Janeiro

Programa de Pós-Graduação em Genética Evolutiva e Biologia Molecular

Programa de Pós-Graduação em Biologia de Água Doce e Pesca Interior

Programa de Pós-Graduação em Ecologia e Recursos Naturais

Programa de Pós-Graduação em Ciências Biológicas – Genética

Programa de Pós-Graduação em Ciências Biológicas – Ecologia

Coordenação de Aperfeiçoamento de Pessoal do Ensino Superior

Fundação de Amparo à Pesquisa do Estado de São Paulo

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Catalogue of MSc Dissertations and PhD Theses

Note: Titles of Theses and Dissertations maintain the taxonomic and/or systematic data as they were originally employed. The classification of some species and genera were later updated by review studies (Reis et al. 2003; Oliveira et al. 2011; FishBase), according to the section: taxon/taxa analyzed.

I. ORDER CHARACIFORMES

I.1. Family

I.1.1. Genus Baird & Girard, 1854

I.1.1.1. MSc Dissertation by Sandra Morelli (1981): Aspectos citogenéticos do gênero (, ) / Cytogenetic studies in the genus PageBreak (, ). Taxa analyzed: (Cuvier, 1819), (Linnaeus, 1758), Britski, 1964, (Jenyns, 1842) – UFSCar / PPGERN / CNPq

I.1.1.2. PhD Thesis by Orlando Moreira Filho (1989): A diversidade no complexo (, , ). Análises citogenéticas e morfológicas. / Diversity investigation in the complex (, , ). Cytogenetic and morphological analyses. Taxon analyzed: – UFSCar / PPGERN

I.1.1.3. MSc Dissertation by Heloisa Helena Paganelli (1990): A variabilidade cromossômica no gênero (, ) e seu significado para a sistemática e evolução do grupo / Chromosomal variability in the genus (, ) and its significance for the systematics and evolution of the group. Taxa analyzed: (Jenyns, 1842) -UFSCar / PPGERN

I.1.1.4. MSc Dissertation by Álvaro José Justi (1993): Caracterização cariotípica de populações de () de bacias hidrográficas distintas / Karyotype characterization of populations () from different river basins. Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.1.1.5. MSc Dissertation by Vera Elisa Vicente (1994): Estudo do cromossomo B em três populações de () / B chromosome analysis in three populations (). Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.1.1.6. MSc Dissertation by Issakar Lima Souza (1996): Estudos citogenéticos em populações de () pertencentes a dois riachos de diferentes bacias do Sudeste Brasileiro / Cytogenetic studies in populations of () from two different river basins of Southeastern Brazil.Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.1.1.7. PhD Thesis by Carlos Alberto Mestriner (1997): Caracterização molecular e citológica do DNA repetitivo de (, ) portador de cromossomos supranumerários / Molecular and cytological characterization of repetitive DNAs in (, ) carrying supernumerary chromosomes. Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.1.1.8. MSc Dissertation by María Pía Heras (1998): Estudos citogenéticos em () de alguns rios do Brasil / Cytogenetic studies in () from some Brazilian rivers. Taxon analyzed: populations – UFSCar / PPGGEv / CNPq

I.1.1.9. MSc Dissertation by Daniela Morilha Néo (1999): Distribuição dos cromossomos B presentes em () ao longo do Ribeirão Grande na região de Campos do Jordão–SP / B chromosomes distribution in () along the Grande Stream, Campos do Jordão region–SP. Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.1.1.10. PhD Thesis by Dagmar Aparecida de Marco Ferro (2000): Análises cariotípicas dos cromossomos B em populações de (, ) / Karyotypic analyses of B chromosomes in populations (, ). Taxon analyzed: – UFSCar / PPGGEv / CNPq

I.1.1.11. MSc Dissertation by Monique Mantovani (2001): Citogenética comparativa entre populações de () da bacia do rio Paranapanema / Comparative cytogenetics among populations of () from the Paranapanema River basin. Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.1.1.12. MSc Dissertation by Luciano Douglas dos Santos Abel (2001): A variabilidade do complexo de espécies () como estratégia adaptativa. Estudo da diversidade cariotípica do grupo com ênfase em populações da bacia do rio São Francisco / The variability of the species complex () as an adaptive strategy. Analysis of the karyotypic diversity emphasizing populations from the São Francisco River basin. Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.1.1.13. PhD Thesis by Rubens Pazza (2005): Contribuição citogenética à análise da biodiversidade em (, ) / Cytogenetic contribution to biodiversity analysis in (, ). Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.1.1.14. PhD Thesis by Wellington Adriano Moreira (2009): Análise citogenética de espécies de () na região de transposição do rio Piumhi / Cytogenetic analysis of species () from the transposition region of the Piumhi River. Taxa analyzed: , , (Lütken, 1875), Garutti & Britski, 2000 – UFSCar / PPGGEv / FAPESP

I.1.2. Genus Eigenmann, 1907

I.1.2.1. MSc Dissertation by Adriane Pinto Wasko (1996): Estudos citogenéticos no gênero (, ). Uma abordagem citotaxonômica-evolutiva / Cytogenetic studies in the genus (, ). A cytotaxonomic-evolutionary approach. Taxa analyzed: sp A-E, Reinhardt, 1867 – UFSCar / PPGGEv / CNPq

I.1.3. Genus Eigenmann, 1903

I.1.3.1. MSc Dissertation by Elisangela Santana de Oliveira Dantas (2002): Estudos citogenéticos entre três espécies de (, ) de localidades diferentes / Cytogenetic studies among three species (, ), from different localities Taxa analyzed: (Steindachner,1907), Eigenmann, 1908, sp. – UFSCar / PPGGEv / FAPESP

I.1.4. Subfamily

I.1.4.1. Genus Müller & Troschel, 1844

I.1.4.1.1. MSc Dissertation by Vladimir Pavan Margarido (1995): Uma contribuição à citogenética de (, ) / A contribution to cytogenetics (, ). Taxa analyzed: Günther, 1864, Lütken, 1875, (Valenciennes,1850), Perugia, 1897), (Günther, 1869), Steindachner, 1877, sp.- UFSCar / PPGGEv / CAPES

I.1.4.1.2. PhD Thesis by Adriane Pinto Wasko (2000): Marcadores cromossômicos e moleculares no gênero (): uma contribuição à biologia evolutiva e à conservação biológica destes peixes / Chromosomal and molecular markers in the genus (): a contribution to its evolutionary and conservation biology. Taxa analyzed: , , , , , , sp. – UFSCar / PPGGEv / FAPESP/CNPq

I.1.5. Miscelaneous groups in

I.1.5.1. MSc Dissertation by Ana Luiza de Brito Silva Portela (1987): Citogenética de peixes da subfamília () / Fish cytogenetics of the subfamily (). Taxa analyzed: Spix et Agassiz, 1829, , Eigenmann, 1908, (Steindachner,1907), Eigenmann, 1908, Eigenmann, 1908 – USP / PPGCB – Gene / CAPES

I.1.5.2. MSc Dissertation by Sandra Cristina Pfister (1997): Contribuição aos estudos cariotípicos da família da bacia do rio São Francisco – Três Marias (MG) / A contribution to the karyotypic studies in the family from the São Francisco River basin – Três Marias (MG).Taxa analyzed: (Reinhardt, 1851), (Eigenmann, 1914), (Günther, 1864), Ellis, 1911, – UFSCar / PPGGEv / CNPq

I.1.5.3. PhD Thesis by Issakar Lima Souza (2003): rDNAs nucleares e bandamentos cromossômicos em e () / Nuclear rDNAs and chromosome banding in and (). Taxa analyzed: , (Cuvier, 1816), Valenciennes, 1850 – UFSCar / PPGGEv / CNPq / FAPESP

I.1.5.4. MSc Dissertation by Wellington Adriano Moreira Peres (2005): Análise da diversidade cariotípica de da bacia do São Francisco / Analysis on karyotypic diversity of fishes from the São Francisco River basin. Taxa analyzed: , (Eigenmann, 1915), (Lütken,1875), , , (Lütken, 1875), – UFSCar / PPGGEv / FAPESP

I.2. Family

I.2.1. Genus Agassiz, in Spix et Agassiz, 1829

I.2.1.1. MSc Dissertation by Erica Pauls (1981): Evidências de um sistema de cromossomos supranumerários em Steindachner, 1881 (, ) / Evidences for a supernumerary chromosome system in Steindachner, 1881 (, ). Taxon analyzed: (Valenciennes, 1836), cited as – UFSCar / PPGERN / CNPq

I.2.1.2. PhD Thesis by Erica Pauls (1985): Considerações sobre evolução cromossômica e sistema de cromossomos supranumerários em espécies do gênero (, ) / Considerations on chromosomal evolution and supernumerary chromosome systems in species (, ). Taxa analyzed: (cited as ), Kner, 1859, Steindacher, 1875 (cited as Steindachner, 1911), Agassiz, 1829, (rejected by ICZN; under synonymy of ), Valenciennes, 1850 (cited as Lütken, 1875, Agassiz, 1829 – UFSCar / PPGERN / CNPq

I.2.1.3. MSc Dissertation by Zélia Isabel Cavallaro (1992): Estudos comparativos sobre os cromossomos B de Steindachner, 1881 (, ) / Comparative studies on B chromosomes of Steindachner, 1881 (, ). Taxon analyzed: , cited as – UFSCar / PPGERN / CAPES

I.2.1.4. PhD Thesis by Terumi Hatanaka (2000): Marcadores cromossômicos e moleculares no peixe : uma espécie de interesse econômico no rio São Francisco / Chromosomal and molecular markers in , a fish species with economic significance from the São Francisco River.Taxon analyzed: (cited as : rejected by ICZN)- UFSCar / PPGGEv / FAPESP

I.2.1.5. PhD Thesis by Célia Maria de Jesus (2001): Caracterização de sequências repetitivas no genoma de () portador de cromossomos B / Characterization of repetitive sequences in the genome of () carrying B chromosomes. Taxon analyzed: – UFSCar / PPGGEv / CNPq / FAPESP

I.3. Family

I.3.1. MSc Dissertation by Orlando Moreira Filho (1983): Estudos na família (, – cited as ) da bacia do rio Passa-Cinco (SP): aspectos citogenéticos e considerações correlatas / Studies in species (, ) from the Passa-Cinco River Basin (SP): cytogenetic and correlated considerations.Taxa analyzed: (Steindachner, 1879), Campos, 1944, (Eigenmann, 1907), Kner, 1859 (cited as Eigenmann & Norris, 1900) – UFSCar / PPGERN

I.3.2. MSc Dissertation by Célia Maria de Jesus (1996): Contribuição aos estudos citogenéticos na família () / Contribution to cytogenetic studies in the family (). Taxa analyzed: (cited as ), (Allen, 1942) (cited as sp), Garavello, 1977- UFSCar / PPGGEv / FAPESP

I.3.3. PhD Thesis by Vera Elisa Vicente (2001): Estudos citogenéticos e moleculares em e correlações com outras espécies da família () / Cytogenetic and molecular studies in and correlations with other species. Taxa analyzed: Reinhardt, 1866, (cited as ) – UFSCar / PPGGEv / CNPq

I.3.4. MSc Dissertation by Elisangela Bellafronte da Silva (2004): Estudos citogenéticos comparativos em espécies do gênero () / Comparative cytogenetics in species ().Taxon analyzed: – UFSCar / PPGGEv / CNPq

I.3.5. PhD Thesis by Josiane Baccarin Traldi (2015): Investigação do papel dos DNAs repetitivos na evolução cromossômica de espécies de (, ) / Investigation on the role of repetitive DNAs in the chromosomal evolution of species (, ). Taxa analyzed: Pavanelli & Britski, 2003, Travassos, 1957, Pavanelli & Britski, 2003, Fowler, 1941, sp. 1, sp. 2 – UFSCar / PPGGEv / FAPESP

I.4. Family

I.4.1. MSc Dissertation by Lucia Giuliano Caetano (1986): Estudo citogenético em (, ) de diferentes bacias hidrográficas brasileiras / Cytogenetic studies in (, ) from different Brazilian river basins. Taxon analyzed: (Agassiz, 1829) – UFSCar / PPGERN / CNPq

I.4.2. MSc Dissertation by Jorge Abdala Dergam dos Santos (1989): O cariótipo de em populações da bacia do São Francisco e do Alto Paraná. Considerações citotaxonômicas / The karyotype of populations from the São Francisco and High Paraná River basins. Cytotaxomic considerations. Taxon analyzed: (Block, 1794) karyomorphs D, F – USP / PPGCB – Gene / CAPES

I.4.3. PhD Thesis by Sandra Morelli (1998): Citogenética evolutiva em espécies do gênero , grupo . Macroestrutura cariotípica, heterocromatina constitutiva e regiões organizadoras de nucléolos / Evolutionary cytogenetics in species group. Karyotype macrostructure, constitutive heterochromatin and nucleolus organizing regions. Taxon analyzed: Miranda Ribeiro, 1908 species group – UFSCar / PPGGEv / CNPq

I.4.4. PhD Thesis by Guassenir Gonçalves Born (2000): Estudo da diversidade cariotípica no grupo (, ). Cariótipo 2n=42 PageBreak/ Study on the karyotypic diversity in the species group (, ). The karyotype 2n=42. Taxon analyzed: karyomorphs A, B – UFSCar / PPGGEv / CAPES

I.4.5. MSc Dissertation by Débora Diniz Bezerra (2002): Estudos citogenéticos populacionais em (, ). Análise da biodiversidade / Population cytogenetic studies in (, ). Biodiversity analysis. Taxon analyzed: – UFSCar / PPGGEv / CNPq

I.4.6. MSc Dissertation by Marcelo Ricardo Vicari (2003): Citogenética comparativa de (, ). Estudos em região divisora de águas das bacias dos rios Tibagi, Iguaçu, Ivaí e Ribeira (Ponta Grossa, PR) / Comparative cytogenetics of (, ). Studies in the water divisor region of the Tibagi, Iguaçu, Ivaí and Ribeira Rivers (Ponta Grossa, PR). Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.4.7. MSc Dissertation by Marcelo de Bello Cioffi (2010): Marcadores cromossômicos em (, ). Citogenética comparativa entre cariomorfos / Chromosome markers in (, . Comparative cytogenetics among karyomorphs. Taxon analyzed: karyomorphs A, B, C, D – UFSCar / PPGGEv / FAPESP

I.4.8. MSc Dissertation by Daniel Rodrigues Blanco (2010): Caracterização citogenética em populações alopátricas do gênero , com enfoque nos grupos e / Cytogenetic characterization of allopatric populations of the genus, focusing on the and groups. Taxa analyzed: , (Valenciennes, 1847), (Günther, 1864) – UFSCar / PPGGEv / FAPESP

I.4.9. PhD Thesis by Marcelo de Bello Cioffi (2011): Evolução cromossômica na família . Mapeamento citogenético de DNAs repetitivos e microdissecção de cromossomos sexuais / Chromosome evolution in the family. Cytogenetic mapping of repetitive DNAs and microdissection of sex chromosomes. Taxa analyzed: karyomorphs A, B, C, D, (Bloch & Schneider, 1801) karyomorphs A, D – UFSCar / PPGGEv / FAPESP

I.4.10. MSc Dissertation by Nícolas Fernandes Martins (2013): Diferenciação cromossômica em (, ) / Chromosomal differentiation in (, ). Taxon analyzed: karyomorphs A, C – UFSCar / PPGGEv / CAPES

I.4.11. MSc Dissertation by Juliana de Fátima Martinez (2014): (, ): um complexo de espécies. Estudos citogenéticos e moleculares / (, ): a species complex. Cytogenetic and molecular analyses. Taxon analyzed: – UFSCar / PPGGEv / FAPESP

I.4.12. MSc Dissertation by Ezequiel Aguiar de Oliveira (2015): Evolução cromossômica em peixes da família (). Citogenética compaPageBreakrativa entre espécies do gênero / Chromosome evolution in the fish family (). Comparative cytogenetics among species. Taxa analyzed: , (Agassiz, 1829), , – UFSCar / PPGGEv / CAPES

I.5. Family (Former , )

I.5.1. MSc Dissertation by Marta Margarete Cestari (1990): Diferenciação cromossômica no gênero La Cèpede, 1803 e evolução do cariótipo em (, ) / Chromosomal differentiation in the genus La Cèpede, 1803 and karyotypic evolution in (, ). Taxa analyzed: Kner, 1858, Valenciennes, 1850, (Lütken, 1875) – UFSCar / PPGERN / CNPq

I.5.2. PhD Thesis by Marta Margarete Cestari (1996): Estudos citogenéticos e genético-bioquímicos do gênero (, ) / Cytogenetic and genetic-biochemical studies in the genus (, ).Taxa analyzed: , Valenciennes, 1837 -UFSCar / PPGGEv / CAPES

I.5.3. PhD Thesis by Jorge Ivan Rebelo Porto (1999): Análises cariotípicas e sequenciamento de DNA mitocondrial em populações de (, ) da bacia amazônica / Karyotypic analyses and mtDNA sequencing in populations (, ) from the Amazon Basin. Taxon analyzed: Jégu, Santos & Ferreira, 1989 – INPA/BADPI/CNPq

I.5.4. PhD Thesis by Celeste Mutuko Nakayama (2007): Citogenética molecular comparativa do DNAr 18S e DNAr 5S em piranhas (, ) da Amazônia Central / Comparative molecular cytogenetics of the 18S and 5S rDNAs in piranhas (, ) from the Central Amazon. Taxa analyzed: Merchx, Jégu & Santos, 2000, Kner, 1858, Fink & Machado-Allison, 1992, (Linnaeus, 1766), (Valenciennes, 1850), Kner, 1858, , Kner, 1858, (Steindachner, 1908), (Cuvier, 1819) – UFSCar / PPGGEv / CNPq

I.6. Family (former , )

I.6.1. PhD Thesis by José das Neves Falcão (1988): Caracterização cariotípica em peixes do gênero (, , ) / Karyotypic characterization of fish (, , ). Taxa analyzed: (Garman, 1890), (Spix & Agassiz, 1829) (cited as Cope, 1872), Cope, 1872, (Cope, 1872), (Valenciennes, 1850) (cited as (Günther, 1864) – USP / PPGCB – Gene / CAPES

I.6.2. PhD Thesis by Roberto Ferreira Artoni (1999): Citogenética do sistema de cromossomos sexuais ZZ/ZW no gênero (, ) / CyPageBreaktogenetics of the ZZ/ZW sex chromosome system in the genus (, ). Taxa analyzed: , cited as , (Garman, 1890), (Kner, 1858) (cited as (Günther, 1874) – UFSCar / PPGGEv / FAPESP

I.6.3. PhD Thesis by Débora Diniz Bezerra (2007): Origem e diferenciação do sistema de cromossomos sexuais ZZ/ZW em (, ). Citogenética, mapeamento de genes ribossomais e microdissecção cromossômica / Origin and differentiation of the ZZ/ZW sex chromosome system in (, ). Cytogenetic mapping of ribosomal genes and chromosomal microdissection. Taxa analyzed: , , (Castelnau, 1855), , , , – UFSCar / PPGGEv / CNPq

I.6.4. PhD Thesis by Cássia Fernanda Yano (2016): Estudos evolutivos no gênero (, ) com enfoque na diferenciação do sistema de cromossomos sexuais ZZ/ZW / Evolutionary studies in the genus (, ) foccusing on the differentiation of the ZZ/ZW sex chromosome system. Taxa analyzed: , , , (Jardine, 1841), , , , Malabarba, 2004 – UFSCar / PPGGEv / CAPES

I.7. Family

I.7.1. PhD Thesis by Eliana Feldberg (1990): Estudos citogenéticos em doze espécies de peixes da família () da Amazônia Central / Cytogenetic studies of twelve species () from the Central Amazon.Taxa analyzed: (Steindachner, 1876), (Cope, 1878), (Spix & Agassiz, 1829), (Eigenmann & Eigenmann, 1889), (Kner, 1858), (Steindachner, 1876), (Linnaeus, 1766), sp, (Kner, 1858), (Müller & Troschel, 1844), (Steindachner, 1882) – INPA / BADPI

I.7.2. MSc Dissertation by Paulo Cesar Venere (1991): Citogenética comparativa de peixes da família () / Comparative cytogenetics of fish (). Taxa analyzed: (Quoy et Gaimard, 1824), (Fernández-Yépez, 1948), (Steindachner, 1881), (Britski, 1980), (Hensel, 1870), sp., (Steindachner, 1874), sp., (Fernández-Yépez, 1948), (Eigenmann & Eigenmann, 1889) – UFSCar / PPGERN / CAPES

I.7.3. PhD Thesis by Rosângela Martins de Oliveira (2011): Citogenética clássica e molecular de três espécies de curimatídeos, com ênfase no cromossomo B de (, ) / Conventional and molecular cytogenetics in three curimatid species, with emphasis on the B chromosome of (, ). Taxa analyzed: , , – UFSCar / PPGGEv / CAPES/CNPq

I.8. Family (former , )

I.8.1. MSc Dissertation by Carlos Suetoshi Miyazawa (1991): Estudos citogenéticos em peixes do grupo (, ), de distintas bacias hidrográficas / Cytogenetic studies in (, ) species from different hydrographic basins.Taxa analyzed: Gomes, 1947, Eigenmann, 1909, Travassos, 1947, sp. – UFSCar / PPGERN / CAPES

I.9. Family

I.9.1. MSc Dissertation by Carlos Alberto Mestriner (1993): Análise das regiões organizadoras de nucléolo e investigação do sistema XX/XY descrito para (, ) / Analyses of the nucleolus organizer regions and investigation of the XX/XY sex system of (, ). Taxon analyzed: Campos, 1945 – UFSCar / PPGGEv / FAPESP

I.9.2. MSc Dissertation by Wagner Franco Molina (1995): Cromossomos sexuais e polimorfismo cromossômico no gênero (, ) / Sex chromosomes and chromosomal polymorphism in the genus (, ).Taxa analyzed: Valenciennes, 1850, (Valenciennes, 1836), Lütken, 1875, – UFSCar / PPGGEv / CAPES

I.9.3. MSc Dissertation by Cesar Martins (1997): Novas contribuições à citogenética de (, ). Citotaxonomia e filogenia no gênero / New contributions to cytogenetics of (, ). Cytotaxonomy and phylogeny of the genus . Taxa analyzed: Garavello & Britski, 1990, Kner, 1858, (Steindachner, 1875), (Valenciennes, 1850), Spix & Agassiz, 1829, (Boulenger, 1900), Kner, 1858, Garavello & Britski, 1990 – UFSCar / PPGGEv / CNPq

I.9.4. MSc Dissertation by Suelen Regina Lopes Krichanã (1999): Contribuição ao estudo citogenético da família (, ) na região Amazônica / Contribution to the cytogenetics of the family (, ) from the Amazon region- Taxa analyzed: (Kner, 1858), Steindachner, 1876, Borodin, 1929, , , Eigenmann, 1912, , – UFSCar / PPGGEv

I.9.5. PhD Thesis by Cesar Martins (2000): Organização do DNA ribossômico 5S no genoma de peixes, com ênfase em / Organization of the 5S rDNA in the fish genome, with emphasis on . Taxa analyzed: , (Block, 1794), , , Fowler, 1941, Fowler, 1914, Steindachner, 1875, , , , , , – UFSCar / PPGGEv / FAPESP

I.9.6. PhD Thesis by Vladimir Pavan Margarido (2000): Uma contribuição à citogenética de , com ênfase na variabilidade das regiões organizadoras de nucléolos no gênero (, ) / Contribution to cytogenetics, with emphasis on the variabilty of the nucleolar organizing regions in the genus (, ). Taxa analyzed: Steindachner, 1875, , , , , (Block, 1794), , , Garavello and Britski, 1988, Steindachner, 1875, , Steindacher, 1915, , , L. , 1858, Lütken, 1875, Borodin, 1929 – UFSCar / PPGGEv / CNPq

I.9.7. PhD Thesis by Cecília Teixeira de Aguilar (2001): Estudos citogenéticos e moleculares em populações brasileiras de (, ) / Cytogenetic and molecular studies in Brazilian populations of (, ). Taxon analyzed: (Valenciennes, 1850) – UFSCar / PPGGEv / CAPES

II. ORDER SILURIFORMES

II.1. Family

II.1.1. MSc Dissertation by Alberto Sergio Fenocchio (1987): Polimorfismo cromossômico em (, citado como ) / Chromosomal polymorphism in (, ). Taxon analyzed: (Quoy & Gaimard, 1824) (cited as (Valenciennes, 1840) – USP / PPGCB – Gene / CNPq

II.2. Family

II.2.1. MSc Dissertation by Roberto Ferreira Artoni (1996): Estudos citogenéticos na família , com especial ênfase no gênero Lacepede (1803) – , / Cytogenetic studies in the family , with special emphasis on the genus Lacepede (1803) – , . Taxa analyzed: (Ihering, 1911), (Ihering, 1905), (Regan, 1908), Kner, 1854, (Valenciennes, 1840) (cited as Valenciennes in Cuvier et Valenciennes, 1840), sp., Spix & Agassiz, 1829, sp., (Steindachner, 1867), (Peters, 1877), sp., Fowler, 1940 -UFSCar / PPGGEv / CNPq

II.2.2. PhD Thesis by Lúcia Giuliano-Caetano (1998): Polimorfismo cromossômico Robertsoniano em populações de (, ) / Robertsonian chromosomal polimorphism in populations (, ).Taxa analyzed: (Boulenger, 1900), Langeani & Araujo, 1994 -UFSCar / PPGGEv / CAPES

II.2.3. MSc Dissertation by Fábio Mendes Camilo (2004): Estudos citogenéticos de algumas espécies de peixes da família pertencentes à bacia do rio PageBreakPiracicaba / Cytogenetic studies in fish species from the Piracicaba River basin.Taxa analyzed: Britsky, 1997, (Eigenmann & Kennedy, 1903), -UFSCar / PPGGEv

II.2.4. PhD Thesis by Sandra Mariotto (2008): Estudo citogenético clássico e molecular em quinze espécies da tribo (, ) de três bacias hidrográficas brasileiras / Conventional and molecular cytogenetic studies in 15 species (, ) from three Brazilian hidrographic basins. Taxa analyzed: Eigenmann & Eigenmann, 1889, and other not identified species – UFSCar / PPGGEv / CNPq / CAPES

II.2.5. MSc Dissertation by Ernani de Oliveira Mendes Neto (2008): Estudos citogenéticos em algumas espécies de (, ) da região de transposição do rio Piumhi para o rio São Francisco / Cytogenetic studies in species (, ) from the transposition region of the Piumhi River into the São Francisco River. Taxa analyzed: , sp.1, sp. 2, – UFSCar / PPGGEv / FAPESP

II.2.6. PhD Thesis by Marceleia Rubert (2011): Estudos citogenéticos em espécies das tribos Hipostomini e (, ) / Cytogenetic studies in Hipostomini and species (, ). Taxa analyzed: (Regan, 1904), (Regan, 1912), Cardoso & Malabarba, 1999, , Kner, 1854, Valenciennes, 1836, Zawadzki, Weber & Pavanelli, 2008, (Ihering, 1905), (Regan, 1908), Knaack, 1999, (Schubart, 1964), (Ihering, 1905), , , (Regan, 1908) – UFSCar / PPGGEv / CAPES / CNPq

II.2.7. MSc Dissertation by Josiane Baccarin Traldi (2012): Citogenética comparativa em espécies de (, , ). Contribuição da fração repetitiva do genoma para a diversidade cromossômica do grupo / Comparative cytogenetics in species (, , ). Contribution of the repetitive genomic fraction to chromosomal diversity. Taxa analyzed: , , , Oyakawa, Akama & Zanata, 2005 – UFSCar / PPGGEv / FAPESP

II.2.8. PhD Thesis by Daniel Rodrigues Blanco (2012): Estudos citogenéticos clássicos e moleculares em espécies do gênero (, ), com enfoque no papel dos DNAs repetitivos na evolução cariotípica do grupo / Conventional and molecular cytogenetic studies in species (, ), focusing on the role of repetitive DNAs in the karyotypic evolution. Taxa analyzed: Steindachner, 1877, Langeani, Oyakawa & Montoya-Burgos, 2001, Miranda Ribeiro, 1908, Oyakawa, 1993, Rapp Py-Daniel & Oliveira, 2001, Oyakawa, 1993, Miranda Ribeiro, 1939 – UFSCar / PPGGEv / FAPESP

II.3. Family

II.3.1. MSc Dissertation by Roberto Laridondo Lui (2010): Análises comparativas citogenéticas e do DNA mitocondrial em Bleeker, 1862 (, ) coletados no alto rio Paraná, no alto rio São Francisco e no rio Piumhi: um enfoque biogeográfico / Cytogenetic and mtDNA comparative analyses in Bleeker, 1862 (, ) from the upper Paraná, Upper São Francisco and Piumhi Rivers: a biogeographical focus.Taxon analyzed: (Linnaeus, 1766) [cited as (Linnaeus, 1766)] – UFSCar / PPGGEv / FAPESP

II.3.2. PhD Thesis by Roberto Laridondo Lui (2012): Estudos evolutivos em (): citogenética, DNA mitocondrial e DNA satélite / Evolutionary studies in (): cytogenetics, mtDNA and satellite DNA.Taxa analyzed: (Linnaeus, 1766), (Haseman, 1911), (cited as ), (Steindachner, 1877) [cited as (Steindachner, 1877)], sp., (Ihering, 1930), Pavanelli & Bifi, 2009- UFSCar / PPGGEv / FAPESP

III. ORDER PERCIFORMES

III.1. Family

III.1.1. MSc Dissertation by Eliana Feldberg (1983): Estudos citogenéticos em 10 espécies da família (, ) / Cytogenetic studies in ten species (, ). Taxa analyzed: (Agassiz, 1831), (Jenyns, 1842), Eigenmann & Ward, 1907, (Castelnau, 1855), Keckel,1840, Heckel, 1840, (Heckel, 1840) (cited as Heckel, 1840), (Quoy & Gaimard, 1824), (Block, 1791), (Perugia, 1891) -UFSCar / PPGERN / CAPES

III.2. Family

III.2.1. MSc Dissertation by Cecilia Texeira Aguilar (1993): Estudos citogenéticos em peixes da família (- ) ocorrentes na Baía de Guanabara – RJ / Cytogenetic studies in fishes of the family (-) from the Guanabara Bay – RJ. Taxa analyzed: (Quoy & Gaimard, 1824), (Linnaeus, 1766), (Lowe, 1834) (cited as ; not of Linnaeus, 1758), (Bloch,1793), (Cuvier, 1829) – UFRJ / PPGCB – Gene / CAPES

III.3. Family

III.3.1. PhD Thesis by Wagner Franco Molina (2000): Análise da diversidade genética na famíla (, ), utilizando métodos combinados PageBreakde citogenética, marcadores moleculares e morfometria / Analysis of the genetic diversity in the family (, ), employing cytogenetic, molecular and morphometric methods. Taxa analyzed: (Cuvier, 1830), (Castelnau, 1855), (Müller & Troschel, 1848), (Castelnau, 1855), (Emery, 1972), Lubbock & Edwards, 1981, (Linnaeus, 1758), (Guichenot, 1853), (Cuvier, 1830), (Günther, 1880), (Cuvier, 1830), Brevoort, 1856 – UFSCar / PPGGEv / CAPES

IV. ORDER OSTEOGLOSSIFORMES

IV.1. Family

IV.1.1. PhD Thesis by Débora Karla Marques (2003): Caracterização genética do pirarucu, (, ) / Genetic characterization of the pirarucu, (, ). Taxon analyzed: (Schinz, 1822) – UFSCar / PPGGEv

V. MISCELANEOUS GROUPS

V.1. MSc Dissertation by José das Neves Falcão (1983): Estudos citogenéticos em e (, ) / Cytogenetic studies in and (, ). Taxa analyzed: Order – Family : Menezes, 1969, (Lütken, 1875), Family : (Steindacher, 1879), (Cuvier, 1829), (Günther, 1864), sp., Amaral Campos, 1945 (cited as ) – USP / PPGCB – Gene / CAPES

V.2. PhD Thesis by Mario Jorge Ignacio Brum (1994): A evolução cariotípica dos teleósteos marinhos e suas correlações com a filogenia deste grupo / Karyotype evolution of marine teleosts and its correlation with the phylogeny of the group. Taxa analyzed – Order – Family : (Spix & Agassiz, 1829); Order –Family : (Cuvier, 1830); Family : (Linnaeus, 1758) – Order – Family : Gilbert, 1900 – UFSCar / PPGGEv

V.3. MSc Dissertation by Lilian Cristina Jorge (1995): Estudos citogenéticos comparativos de algumas espécies de peixes da região de Corrientes (Argentina) com as do Alto Paraná / Comparative cytogenetic studies of some fish species from the Corrientes region (Argentina) with those of the upper Paraná River basin.Taxa analyzed – Order – Family : ; Family : ; Family : ; Family : , – UFSCar / PPGGEv / FAPESP.

V.4. MSc Dissertation by Margareth Maria de Oliveira Correa (1995): Contribuição à citotaxonomia dos (-). Estudos citogenéticos em espécies do litoral do Rio de Janeiro, Brasil / Contribution to the cytotaxonomy of (-Teloestei). Cytogenetic studies in coastal species from Rio de Janeiro, Brazil. Taxa analyzed – Order –Family : (Linnaeus, 1758); Family : Cuvier, 1829; Meek & Hildebrand, 1928; Family : (Block, 1793) – UFRJ / PPGCB-Ecol / CNPq

V.5. PhD Thesis by Carlos Suetoshi Miyazawa (1997): Citogenética de caracídeos do rio Paraguai. Análises citotaxonômica-evolutivas e considerações biogeográficas / Cytogenetics of characids from the Paraguay River. Cytotaxonomic and evolutionary analyses and biogeographical considerations. Taxa analyzed: Order – Family : Menezes, 1992; Family : (Kner, 1858), (Eigenmann & McAtee, 1907) (cited as ); Family : (Eigenmann,1907), (Cuvier, 1816), sp.; (Jenyns, 1842), (Perugia, 1891), (Boulenger, 1895), (Kner, 1858); Family : sp., Family : (Kner, 1858) – UFSCar / PPGGEv / CAPES

V.6. PhD Thesis by Paulo Cesar Venere (1998): Diversificação cariotípica em peixes do médio rio Araguaia, com ênfase em e (, ) / Karyotype diversification in fishes from the middle Araguaia River, with emphasis on and (, ). Taxa analyzed: Order – Family : , Steindachner, 1876, sp., Myers, 1950, Géry, 1964; Family Prochilodontide: ; Family : (Kner, 1858); Family : (Steindachner, 1911), Vari & Williams Vari, 1989, Vari, 1989, Eigenmann & Eigenmann, 1889; Family : Myers, 1927, (Bloch, 1794), (Eigenmann & Myers, 1927); Family : sp., (Cope, 1870), Müller & Troschel, 1844; Order – Family : Kindle, 1895, (Günther, 1868), sp., sp.; Family : (cited as ); Family : (Valenciennes, 1840), cited as (Ranzani, 1841); Family : Linnaeus, 1758 – UFSCar / PPGGEv / CAPES

V.7. MSc Dissertation by Paulo Roberto Antunes de Mello Affonso (2000): Caracterização citogenética de peixes de recifes de corais das famílias e () / Cytogenetic characterization of coral reef fishes PageBreakof the and families (). Taxa analyzed: Order – Family : Burgess, 1974, (Linnaeus, 1758), (Block, 1795), (Linnaeus, 1758), (Block, 1787); Family : Linnaeus, 1758 – UFSCar / PPGGEv / CNPq

V.8. MSc Dissertation by Marilza Barbosa de Almeida Marques (2002): Estudos citogenéticos em e (), espécies endêmicas do rio São Francisco / Cytogenetic studies in and (), endemic species from the São Francisco River.Taxa analyzed: Order – Family : (Valenciennes, 1840); Family : Steindachner, 1876 – UFSCar / PPGGEv

V.9. MSc Dissertation by Karine Frehner Kavalco (2003): Contribuição citogenética à análise da biodiversidade da ictiofauna das nascentes do rio Paraitinga. / Cytogenetic contribution to the biodiversity analysis of the fish fauna from the headwaters of the Paraitinga River. Taxa analyzed: Order – Family : Steindachner, 1877, (Steindachner, 1877), (Steindachner, 1877), sp.; Order – Family : , Eigenmann, 1908, Eigenmann, 1908, Eigenmann, 1908, – UFSCar / PPGGEv / FAPESP

V.10. PhD Thesis by Liano Centofante (2003): Citogenética comparativa entre ictiofaunas isoladas por um divisor de águas em regiões limítrofes de duas bacias hidrográficas na Serra da Mantiqueira / Comparative cytogenetics of fish fauna from neighboring regions of two hydrographic basins isolated by a watershed in the Serra da Mantiqueira. Taxa analyzed: Order – Family : Miranda Ribeiro, 1939; Family : sp.; Order – Family – , , (Eigenmann, 1907); Family : (cited as ), Ingenito & Buckup, 2005 (cited as sp); Family : Travassos, 1956, Eigenmann, 1909, Travassos, 1949, Travassos, 1955 – UFSCar / PPGGEv / CNPq / CAPES

V.11. MSc Dissertation by Caroline Garcia (2005): Contribuições aos estudos citogenéticos em algumas espécies de cinco famílias de do rio São Francisco / Contributions to cytogenetics of some species of three families from the São Francisco River. Taxa analyzed: Order – Family : (cited as ), (Borodin, 1927) cited as (Borodin, 1927); Family : (Lütken, 1874); Family : ; Family : (Lütken, 1874), Lacepède, 1803, sp., (Humboldt, 1821) cited as (Humboldt, 1821) – UFSCar / PPGGEv / FAPESP

V.12. PhD Thesis by Marcelo Ricardo Vicari (2006): Diversidade de peixes residentes em cabeceiras de rios. Uma abordagem cromossômica em três diferentes biomas aquáticos da região Sul do Brasil / Fish diversity from river headwaters. A chromosomal approach in three biomes from South Brazil. Taxa analyzed: Order – Family : (Jenyns, 1842), Steindachner, 1910; Order – Family : sp.; Family : , Eigenmann, 1908; Family : ; Order – Family : , (Jenyns, 1842) cited as (Jenyns, 1842) – UFSCar / PPGGEv / FAPESP

V.13. MSc Dissertation by Maressa Ferreira Neto (2008): Análise citogenética em algumas espécies de peixes de uma região divisora de águas entre riachos de bacias hidrográficas distintas / Cytogenetic analysis in fish species from a dividing water region of streams belonging to different river basins. Taxa analyzed: Order – Family : , , ; Family : ; Family : ; Order – Family : Linnaeus, 1758; Family : sp.; Order – Family : – UFSCar / PPGGEv / CAPES / CNPq

V.14- PhD Thesis by Elisangela Bellafronte da Silva (2009): Citogenética clássica e molecular em peixes Neotropicais. Estudos comparativos entre bacias hidrográficas com ênfase em região de transposição de rio / Conventional and molecular cytogenetics in Neotropical fishes. Comparative studies among river basins with emphasis on a river transposition region. Taxa analyzed: Order – Family : , Albert & Fernandes-Matioli, 1999; Family : (Valenciennes, 1836), sp. – UFSCar / PPGGEv / CNPq / CAPES

V.15. PhD Thesis by Daniel Luis Zanella Kantek (2010): Citogenética de espécies de da região de transposição do rio Piumhi (MG) / Cytogenetics of species from the transposition region of the Piumhi River (MG). Taxa analyzed: Order – Family : (cited as ); Family : Ribeiro & Lucena, 2006; Family : (Gomes, 1956); Schubart & Gomes, 1959, (Lütken, 1874), sp. A, sp. B, (Lütken, 1874), Family : Lütken, 1874 – UFSCar / PPGGEv / CNPq / CAPES

Final remarks

Two general trends were found among the Neotropical fishes regarding the karyotype evolution. In fact, a significant number of families were characterized by conPageBreakservative karyotypes, in contrast to others with highly divergent ones. , and species, for example, exhibit relatively homogeneous karyotypes at the macrostructural level, contrasting with the high chromosomal diversity found among and species (Bertollo et al. 1986). It is noteworthy that karyotype features appear to be correlated with their lifestyle and ecological habits, since more dispersive and migratory species usually disclose more stable karyotypes when compared to those with low vagility and organized in small local populations (Bertollo et al. 1986; Blanco et al.2011; Oliveira et al. 2015). Indeed, many local populations were evidenced as having particular karyotypes, pointing to a large number of species complexes and the cryptic biodiversity present in the Neotropical fish fauna, as especially highlighted in the and families (Moreira-Filho and Bertollo1991; Bertollo 2007; Cioffi et al. 2012a). In fact, many sympatric, or even syntopic, karyomorphs do not indicate hybridization at the chromosomal level, indicating the absence of gene flow among them and, consequently, corroborating the status of species complexes for some current nominal species (Bertollo et al. 2000).

Reports on chromosomal polymorphisms (Giuliano-Caetano and Bertollo 1988; Vicari et al. 2003; Pazza et al. 2006, 2008; Mariotto et al. 2009), natural triploidy (Morelli et al. 1983; Venere and Galetti Jr. 1985; Giuliano-Caetano and Bertollo 1990; Centofante et al. 2001; Garcia et al. 2003) and broad karyotype evolution by centric fissions (Feldberg et al. 1993), were also emphasized for distinct fish groups. Noteworthy is also the cytogenetic contribution for biogeographical analyzes, clarifying the current fish fauna distribution in some important Brazilian river basins. In this sense, native species, as well as invasive ones due to dispersal events or breakdown of geographic isolation, were clearly identified by chromosomal investigations (Peres et al. 2009; Blanco et al. 2010; Silva et al. 2010; Perez et al. 2012). As a significant example, from two important Brazilian watersheds, namely the São Francisco and Grande rivers share similar morphological characteristics. However, specimens from each one of such rivers were well characterized by their particular chromosomal features. In the early 1960s, a tributary of the Grande River was artificially transposed into the São Francisco river basin, with the consequent breakdown of the geographic isolation of their respective fish fauna. As a consequence, cytogenetic investigation was able to identify representatives of from both basins living in sympatry in the transposition region, as well as individuals with intermediate karyotypes in view of the resulting secondary hybrid zone in such region (Peres et al. 2012).

Over the years, a particular emphasis has been directed on the characterization and the evolutionary process of sex chromosomes. A larger number of Neotropical fish species with well differentiated sex chromosomes occur in comparison to other world regions (Moreira-Filho et al. 1993), carrying simple (ZZ/ZW, XX/XY) and multiple (X1X1X2X2/X1X2Y, XX/XY1Y2, ZZ/ZW1W2) sex chromosome systems (Centofante et al. 2002; Cioffi et al. 2012b), in addition to some others disclosing a nascent or early stage of differentiation (Cioffi and Bertollo 2010; Freitas et al. in press). Usually, sex chromosomes occur as a particular feature for some species within a specific fish group, PageBreakas exemplified in the , , and families (Galetti Jr. et al. 1981, 1995; Moreira-Filho et al. 1985, 1993; Molina et al. 1998; Centofante et al. 2001, 2003; Bertollo et al. 2000; Bertollo 2007; Vicari et al. 2008; Cioffi et al. 2013). As a singular exception, all species of the genus () share a same ZZ/ZW sex chromosome system (Artoni et al. 2001, 2002; Diniz et al. 2008), constituting a special model to investigate the evolution of the sex chromosomes among lower vertebrates. The modern molecular cytogenetics was a key step for understanding the evolutionary process of the sex chromosomes among fishes. This way, the significative role of several classes of repetitive DNAs in the differentiation path of the sex pair, both at its inicial stage (Cioffi and Bertollo 2010; Freitas et al. in press) or more advanced ones (Cioffi et al. 2010, 2011a, b, 2012b; Yano et al. 2014a, b), was clearly highlighted. Notably, whole chromosome painting (WCP) and comparative genomic hybridization (CGH) were able to demonstrate that fish sex chromosomes can have an independent origin even among closely related species (Cioffi et al. 2011c, d; 2013) or, alternatively, a common origin within particular monophyletic groups (Yano et al. 2016).

Besides sex chromosomes, supernumerary or B chromosomes comprise another special feature that stands out in the Neotropical fishes. Such additional elements can be i) as large as the biggest chromosome pair of the karyotype, ii) medium-sized, iii) very small iv) or even characterized as microchromosomes. Two particular models, represented by and , have been subjected to continuous analyses over years. has some morphologically differentiated B chromosomes, although a large and similar in size to the first chromosome pair of the karyotype is the most frequent one (Moreira-Filho et al. 2004). Its origin as an isochromosome was demonstrated by both standard and molecular cytogenetic, including meiotic data (Vicente et al. 1996; Mestriner et al. 2000). A continuous population analysis showed that Bs display a particular dynamism related to environmental and sex conditions in . Indeed, it is noteworthy their gradual decrease in frequency from higher to lower altitudes, until the complete absence in the latter ones (Néo et al. 2000). In addition, an evident sex ratio distortion is associated with these chromosomes. In fact, the mean number of Bs in males is only about 27% of the female one, which matches the male population frequency (Vicente et al. 1996), suggesting that B chromosomes may play a role on sex determination in this species.

Constrasting with , bears a number of very small B chromosomes (Pauls and Bertollo 1983), which also have an intraspecific origin as indicated by molecular cytogenetic and chromosomal banding (Jesus et al. 2003; Artoni et al. 2006). Remarkably, the frequency of these chromosomes was changed over years in close association with their transmission dynamics. In this sense, the average number of Bs increased twice along a time period indicating an accumulation mechanism, but without evidences of additional changes after that. Significantly, the mitotic instability of Bs declined almost 400 times during this same period, reaching a stable transmission. This way, it is likely that the mitotic stabilization was a key process for neutralizing the accumulation process (Cavallaro et al. 2000).

Nowadays, many of such issues so far investigated, in addition to additional approaches on fish biology, are going in advancing in the light of chromosomal, cytogenomic and molecular methodologies currently available. It is hoped that these procedures can provide additional and important advances for the Neotropical fish fauna evolutionary history.