F.E. Porto, A.L.B. Portela-Castro and I.C. Martins-Santos
Published August 24, 2010
Genet. Mol. Res. 9 (3): 1654-1659 (2010)
DOI 10.4238/vol9-3gmr859

About the Authors
F.E. Porto, A.L.B. Portela-Castro and I.C. Martins-Santos

Corresponding author:
F.E. Porto
E-mail: ferreroporto@yahoo.com.br

ABSTRACT

We made a cytogenetic study of Rineloricaria pentamaculata from the Tauá Stream, in the Pirapó River sub-basin in Paraná State, Brazil, focused on the occurrence and origins of the B chromosomes. The diploid number varied from 2n = 56 to 2n = 59, due to the presence of 0 to 3 B microchromosomes of the acrocentric type, which were observed in 92.3% of the specimens (N = 12). These chromosomes were totally heterochromatic, with the C banding technique, and there were inter- and intraindividual numerical differences. Meiotic cells in metaphase I had 28 bivalent chromosomes and 0 to 3 univalent chromosomes. We suggest that the B microchromosomes are centric fragments originated from chromosome rearrangements.

Key words: Heterochromatin; Loricariinae; B microchromosome; Meiosis; Rineloricaria pentamaculata; Univalent