Chromosome Characterization of <i>Astyanax</i> sp B (Characidae, Tetragonopterinae), an Endemic Species of the Iguaçu River, Paraná, Brazil

Abstract

Summary Cytogenetics studies on Astyanax sp B, an endemic species of the Iguaçu River (Paraná, Brazil) were carried out. The specimens showed a standard diploid number of 2nϭ50 chromosomes with a karyotype consisting of 6 metacentric, 24 submetacentric, 6 subtelocentric and 14 acrocentric chromosomes. In addition to the basic karyotype, all the specimens presented 1-2 supranumerary or B chromosomes in mitotic metaphases. Three morphological types of B chromosomes have been identified in population under analysis: an acrocentric-type microchromosome; a metacentric macrochromosome smaller than the first pair of the normal karyotype complement; a small submetacentric chromosome. C-band analysis shows discrete markings in the centromeric regions of various chromosomes which contrast with strongly heterochromatic blocks in the telomeric regions of the long arms of chromosome pairs 20, 21 and 22 (acrocentric). Heterochromatic block-sized heteromorphism has been among homologues of pair 20. The chromosome characterisitics of Astyanax sp B indicate similarity with other species of the genus Astyanax with regard to karyotypic macrostructure, distribution of constitutive heterochromatin (C-band pattern) and occurrence of B chromosomes. Some aspects related B chromosomes in this species are discussed.

Sympatric occurrence of three cytotypes and four morphological types of B chromosomes of Astyanax scabripinnis (Pisces, Characiformes) in the River Ivaí Basin, state of Paraná, Brazil

“…Ne´o, Bertollo and Moreira-Filho (2000) and Ferro, Moreira-Filho and Bertollo (2003) also detected other types of B chromosomes in Astyanax scabripinnis. Fazoli et al (2003) also found three morphological types of B chromosomes in Astyanax sp. B from the River Iguac¸u: a metacentric macrochromosome slightly smaller than the first pair of the chromosome complement, a small submetacentric and an acrocentric-type microchromosome.…”

Cytotaxonomy, heterochromatic polymorphism and natural triploidy of a species of Astyanax (Pisces, Characidae) endemic to the Iguaçu river basin

“…C (Kantek et al, 2003), Astyanax sp. B (Fazoli et al, 2003) and Astyanax altiparanae (Cenci and Margarido, 2003;Kantek et al, 2004) from the Iguaçu river, these species were clearly distinguishable by their cytogenetic features, showing the probable lack of gene flow between them as well as the importance of karyotypic data for the taxonomy of this fish group.…”

“…D did not differ from those of most species of this genus, including A. scabripinnis (Moreira-Filho and Bertollo 1991;Maistro et al, 1998;Souza et al, 1996), Astyanax sp.C (Kantek et al, 2003), Astyanax sp.B (Fazoli et al, 2003) and A. altiparanae (Cenci and Margarido, 2003;Kantek et al, 2004). The C-banding pattern could be considered equilocal on the chromosomes.…”

“…B. (Fazoli et al, 2003), Astyanax. sp.C (Kantek et al, 2003) and A. altiparanae (Cenci and Margarido, 2003;Kantek et al, 2004) from the Iguaçu river, which had less heterochromatin than Astyanax.…”

Cytogenetic analysis of Astyanax laticeps (Cope, 1894) (Ostariophysi: Characidae) from the laguna dos Patos system

“…Such reduced amount of heterochromatin is also observed in other species of this genus, such as A. parahybae (Centofante et al, 2003), Astyanax sp. B (Fazoli et al, 2003), A. altiparanae (Fernandes & Martins-Santos, 2004), and A. jacuhiensis (Pacheco, pers. comm.).…”