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New occurrence of a macro B-chromosome in Astyanax scabripinnis paranae (Pisces, Characiformes, Characidae)

Edson Luis Maistro^I; Fausto Foresti^II; Claudio Oliveira^II

^IDepartamento de Biologia, Instituto de Ciencias Biológicas, Fundação de Ensino e Tecnologia de Alfenas, 37130-000 Alfenas, MG, Brasil
^IIDepartamento de Morfologia, Instituto de Biociências, UNESP, Campus de Botucatu, 18618-000 Botucatu, SP, Brasil. Send correspondence to F.F.

ABSTRACT

Cytogenetic studies performed on 17 specimens (11 females and six males) of Astyanax scabripinnis paranae from the Cascatinha stream showed that this population has 2n=50 chromosomes (8M+22SM+10ST+10A), two chromosome pairs with NORs and conspicuous C-band positive blocks in the terminal position of the long arm of five chromosome pairs. Three females presented 2n=51 chromosomes and the extra chromosome was a large metacentric similar in size and morphology to the first chromosome pair in the karyotype. This accessory chromosome was entirely heterochromatic in C-banded metaphases, which permitted its classification as a supernumerary chromosome. Some aspects related to the morphology of such macro B-chromosomes are discussed.

Keywords: B-chromosome; Astyanax scabripinnis paranae.

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