Nucleolar organizer regions as markers of chromosomal polymorphism in Apareiodon affinis (Pisces, Parodontidae)

Abstract

-Specimens of Apareiodon affinis collected from four sites of the Paraná River (called Lower Paraná, Argentina) were analyzed. This species presents a diploid number of 54 chromosomes, without any apparent sex chromosomal heteromorphism. However, it was possible to verify the occurrence of 10 cytotypes, some of them common to all collected sites, characterizing an structural chromosomal polymorphism. Data obtained from chromosomal banding methods, results further suggest an inter-individual NOR polymorphism. Such variation is possibly caused by pericentric inversions and other chromosomal rearrangements. The 5S rDNA was separated from 18S rDNA clusters, these cistrons seems to present variation, suggesting that other chromosomes could also be involved in the polymorphism. The results obtained confirmed the structural polymorphism in A. affinis.

ZZ/ZW sex chromosome system in an undescribed species of the genus <i>Apareiodon </i>(Characiformes, Parodontidae)

“…chromosomes has a pattern similar to those observed in the karyotypes of other parodontids, as well as the conspicuous heterochromatic block in the longer arm of the W chromosome in those species with a ZZ/ZW sex chromosome system , 1993Jesus et al, 1999;Jesus and Moreira-Filho, 2000a, b;Centofante et al, 2002;Vicente et al, 2003;Jorge and Moreira-Filho, 2004).…”

Chromosome polymorphism in Ancistrus cuiabae Knaack, 1999 (Siluriformes: Loricariidae: Ancistrini)

“…A pericentric inversion concerning the first karyotypic pair was detected in Serrasalmus spilopleura (Serrasalminae) from the Catalão Lake (Amazon basin), with absence of the structural homozygotes (Centofante et al, 2002). Variations concerning the number of the acrocentric chromosomes in Apareiodon affinis (Parodontidae) from the lower Paraná River (Argentina) were also probably due to pericentric inversions, since the diploid number (2n = 54) was constant in the population (Jorge & Moreira-Filho, 2004). Pericentric inversions were also considered in order to explain another few cases of structural polymorphisms, as in Hoplerythrinus unitaeniatus (Erythrinidae) from the Negro River, in the Amazon basin (Giuliano-Caetano & Bertollo, 1988).…”

“…Recently, these variations have been confirmed by the use of fluorescent in situ hybridization (FISH) with 18S rDNA probes (Kavalco et al, 2005;Mantovani et al, 2005;Pazza et al, 2006). However, structural polymorphisms due to other chromosomal rearrangements such as inversions and centric fusions/ fissions are not very common among Neotropical fish, being known mainly among Characiformes (Giuliano-Caetano & Bertollo, 1988;Cestari & Galetti Jr.,1992;Centofante et al, 2002;Jorge & Moreira Filho, 2004;Pazza et al, 2006). In Siluriformes, numerical and/or structural polymorphisms were observed in a few Pimelodidade (Dias & Foresti, 1993;Vasconcelos & Martins-Santos, 2000), Heptapteridae (Vissoto et al, 2001;Kavalco et al, 2004), Hypoptopomatinae (Andreata et al, 1994), Loricariinae (Giuliano-Caetano, 1998), and Trichomycteridae species (Borin & Martins-Santos, 2000).…”

Chromosome polymorphism of heterochromatin and nucleolar regions in two populations of the fish Astyanax bockmanni (Teleostei: Characiformes)

“…3). Chromosome rearrangements due to inversions have been described in some fish groups (Centofante et al, 2002;Jorge & Moreira-Filho, 2004), with some cases involving the NORbearing chromosomes (Porto-Foresti et al, 2004;Mariotto et al, 2009). Based on experimental crosses of farmed stocks of the salmonid Oncorhynchus mykiss, Porto-Foresti et al (2004) suggested that a particular combination of chromosomes with inversions might be lethal in rainbow trout.…”