Astyanax scabripinnis, a small neotropical freshwater fish, is a headwater species living in small tributaries of many Brazilian rivers, where they form isolated populations. This species harbors a B chromosome system in several populations. Among the several kinds of Bs reported in this species, the BM variant, a large metacentric of a similar size to the largest A chromosome, is the most widespread in natural populations. It probably corresponds to the ancestral B type in this species and a very similar B chromosome is also found in other Astyanax species. Strong evidence suggests that this B is an isochromosome showing structural and functional homology between its two arms, as shown by satellite DNA localization and the formation of a ring B univalent during meiosis. The BSM and Bm variants, a large submetacentric and a small metacentric, respectively, represent rare variants and may be derived from structural rearrangements of the BM chromosome. In addition, B microchromosomes (Bmicro) were found in some populations. Frequency analyses in mountain populations have shown that B chromosomes are found in populations located at high altitude, but are absent in populations at low altitude, which is consistent with their parasitic nature, given the ecological peculiarities of both kinds of populations.   

1.
Alves AL, Martins-Santos I: Cytogenetic studies in two populations of Astyanax scabripinnis with 2n = 48 chromosomes (Teleostei, Characidae). Cytologia 67:117–122 (2002).
2.
Araujo ACS, Morelli S: Estudo cariotípico da população de Astyanax scabripinnis (Pisces, Characidae) da nascente do córrego Jataí, Uberlândia-MG. Genet Mol Biol (Suppl) 23:60 (2000).
3.
Britski HA, Sato Y, Rosa ABS: Manual de identificação de peixes da região de Três Marias, com chaves de identificação para os peixes da Bacia do São Francisco (Companhia do Desenvolvimento do Vale do São Francisco – CODEVASF, Brasília 1986).
4.
Cabrero J, Alché JD, Camacho JPM: Effects of B chromosomes of the grasshopper Eyprepocnemis plorans on nucleolar organizer regions activity. Activation of a latent NOR on a B chromosome fused to an autosome. Genome 29:116–121 (1987).
5.
Cabrero J, López-León MD, Bakkali M, Camacho JPM: Common origin of B chromosome variants in the grasshopper Eyprepocnemis plorans. Heredity 83:435–439 (1999).
6.
Camacho JP, Sharbel TF, Beukeboom LW: B-chromosome evolution. Phil Trans R Soc Lond B Biol Sci 355:163–178 (2000).
7.
Caramaschi EP: Distribuição da ictiofauna de riachos das bacias do Tietê e do Paranapanema, junto ao divisor de água (Botucatu, SP). Doctoral Thesis, Universidade Federal de São Carlos, Brazil (1986).
8.
Dias AL: Estudo do complexo sinaptonêmico de peixes Prochilodus lineatus (Prochilodontidae) e Astyanax scabripinnis (Characidae): análises da sinapse dos cromossomos supranumerários. Doctoral Thesis, Universidade Federal de São Carlos, Brazil (1994).
9.
Eigenmann CH: The American Characidae. Mem Mus Comp Zool 43:227–310 (1921).
10.
Fauaz G, Vicente VE, Moreira-Filho O: Natural triploidy and B chromosomes in the Neotropical fish genus Astyanax (Characidae). Braz J Genet 17:157–163 (1994).
11.
Ferro DA, Néo DM, Moreira-Filho O, Bertollo LAC: Nucleolar organizing regions, 18S and 5S rDNA in Astyanax scabripinnis (Pisces, Characidae): populations distribution and functional diversity. Genetica 110:55–62 (2001).
12.
Ferro DA, Moreira-Filho O, Bertollo LAC: B chromosome polymorphism in the fish, Astyanax scabripinnis. Genetica 119:147–153 (2003).
13.
Fowler HW: Os peixes de água doce do Brasil. Arq Zool 6:1–204 (1948).
14.
Géry J: Characoids of the World (TFH Publications, New Jersey 1977).
15.
Lowe-McConnell RH: Speciation in tropical freshwater fishes. Biol J Linn Soc 1:51–75 (1969).
16.
Maistro EL, Foresti F, Oliveira C, Almeida-Toledo LF: Occurrence of macro B chromosome in Astyanax scabripinnis paranae (Pisces, Characiformes, Characidae). Genetica 87:101–106 (1992).
17.
Maistro EL, Foresti F, Oliveira C: New occurrence of a macro B chromosome in Astyanax scabripinnis (Pisces, Characiformes, Characidae). Braz J Genet 17:153–156 (1994a).
18.
Maistro EL, Dias AL, Foresti F, Oliveira C, Moreira-Filho O: Natural triploidy in Astyanax scabripinnis (Pisces, Characidae) and simultaneous occurrence of macro B-chromosomes. Caryologia 47:233–239 (1994b).
19.
Maistro EL, Oliveira C, Foresti F: Comparative cytogenetic and morphological analysis of Astyanax scabripinnis paranae (Pisces, Characidae, Tetragonopterinae). Genet Mol Biol 21:201–206 (1998).
20.
Maistro EL, Foresti F, Oliveira C: R- and G-bands patterns in Astyanax scabripinnis paranae (Pisces, Characiformes, Characidae). Genet Mol Biol 22:201–204 (1999).
21.
Mestriner CA, Galetti Jr PM, Valentini S, Ruiz IGR, Abel LDS, Moreira-Filho O, Camacho JPM: Structural and functional evidence that a B chromosome in the characid fish Astyanax scabripinnis is an isochromosome. Heredity 85:1–9 (2000).
22.
Mizoguchi SMHN: Estudos citogenéticos e morfométricos em populações de Astyanax scabripinnis (Pisces, Characidae). MSc Dissertation. Universidade Estadual de Maringá, Brazil (1996).
23.
Mizoguchi SMHN, Martins-Santos IC: Macro- and microchromosomes B in females of Astyanax scabripinnis (Pisces, Characidae). Hereditas 127:249–253 (1997).
24.
Mizoguchi SMHN, Martins-Santos IC: Cytogenetics and morphometric differences in populations of Astyanax scabripinnis (Pisces, Characidae) from Maringá region, PR, Brazil. Genet Mol Biol 21:55–61 (1998).
25.
Moreira-Filho O, Bertollo LAC: Astyanax scabripinnis (Pisces, Characidae): a species complex. Braz J Genet 14:331–357 (1991).
26.
Moreira-Filho O, Fenocchio AS, Pastori MC, Bertollo LAC: Occurrence of a metacentric macrochromosome B in different species of the genus Astyanax (Pisces, Characidae, Tetragonopterinae). Cytologia 66:59–64 (2001).
27.
Nelson JS: Fishes of the World (John Wiley and Sons, New York 1994).
28.
Néo DM, Bertollo LAC, Moreira-Filho O: Morphological differentiation and possible origin of B chromosomes in natural Brazilian populations of Astyanax scabripinnis (Pisces, Characidae). Genetica 108:211–215 (2000a).
29.
Néo DM, Moreira-Filho O, Camacho JPM: Altitudinal variation for B chromosome frequency in the characid fish Astyanax scabripinnis. Heredity 85:136–141 (2000b).
30.
Porto-Foresti F, Oliveira C, Maistro EL, Foresti F: Estimated frequency of B-chromosomes and population density of Astyanax scabripinnis paranae in a small stream. Braz J Genet 20:377–380 (1997).
31.
Rocon-Stange EA, Almeida-Toledo LF: Supernumerary B chromosomes restricted to males in Astyanaxscabripinnis (Pisces, Characidae). Braz J Genet 16:601–615 (1993).
32.
Salvador LB, Moreira-Filho O: B chromosomes in Astyanax scabripinnis (Pisces, Characidae). Heredity 69:50–56 (1992).
33.
Souza IL, Moreira-Filho O: Cytogenetic diversity in the Astyanax scabripinnis species complex (Pisces, Characidae). I. Allopatric distribution in a small stream. Cytologia 60:1–11 (1995).
34.
Souza IL, Moreira-Filho O, Bertollo LAC: Cytogenetic diversity in the Astyanax scabripinnis species complex (Pisces, Characidae). II. Different cytotypes living in sympatry. Cytologia 60:273–281 (1995).
35.
Stripecke R, Nogueira-Pinto MT, Hackel C, Sazima I: O cariótipo de Astyanax eigenmanniorum (Osteichthyes, Characidae), in XII Congresso Brasileiro de Zoologia (Campinas, Brazil 1985).
36.
Vari RP, Malabarba LR: Neotropical ichthyology: an overview, in Malabarba LR, Reis RE, Vari RP, Lucena AMS, Lucena CA (eds): Phylogeny and Classification of Neotropical Fishes (Edipucrs, Porto Alegre 1998).
37.
Vicente VE: Estudo do cromossomo B em três populações de Astyanax scabripinnis (Pisces, Characidae). MSc Dissertation. Universidade Federal de São Carlos, Brazil (1994).
38.
Vicente VE, Moreira-Filho O, Camacho JPM: Sex ratio distortion associated to the presence of a B chromosome in Astyanax scabripinnis (Teleostei, Characidae). Cytogenet Cell Genet 74:70–75 (1996).
39.
Vieira MMR, Oliveira C, Foresti F: Estudos de conteúdo de DNA em populações de Astyanax scabripinnis (Pisces, Characidae) da região de Botucatu, SP. Braz J Genet (Suppl) 21:63 (1998a).
40.
Vieira MMR, Oliveira C, Foresti F: Padrões de bandeamento G em cromossomos de Astyanax scabripinnis (Pisces, Characidae) da região de Botucatu, SP. In VII Simpósio de Citogenética Evolutiva e Aplicada de Peixes Neotropicais – Londrina, PR. Abstracts, A-18 (1998b).
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