Comparative Cytogenetics of Giant Trahiras <i>Hoplias aimara </i>and <i>H. intermedius </i>(Characiformes, Erythrinidae): Chromosomal Characteristics of Minor and Major Ribosomal DNA and Cross-Species Repetitive Centromeric Sequences Mapping Differ among Morphologically Identical Karyotypes

Abstract

Karyotype and cytogenetic characteristics of 2 species of giant trahiras, Hopliasintermedius, São Francisco river basin, and Hopliasaimara, Arinos river (Amazon basin), were examined by conventional (C-banding, Ag-NOR, DAPI/CMA₃ double-staining) and fluorescent in situ hybridization (FISH) with 5S, 18S rDNA probes and cross-species Cot-1 DNA probing. Both species invariably had diploid chromosome number 2n = 50 and identical karyotypes composed of 10 pairs of metacentric and 15 pairs of submetacentric chromosomes. On the other hand, staining with base-specific fluorochromes (CMA₃, DAPI) and FISH mapping of repetitive DNA sequences showed extensive interspecific differences: while the genome of H. aimara had one submetacentric pair bearing CMA₃-positive (DAPI-negative) sites, that of H. intermedius had 4 such pairs; while FISH with a 5S rDNA probe showed one (likely homologous) signal-bearing pair, that with 18S rDNA displayed one signal-bearing pair in H. intermedius and 2 such pairs in H. aimara. Cross-species FISH probing with Cot-1 DNA prepared from total DNA of both species showed no signals of Cot-1 DNA from H. aimara on chromosomes of H. intermedius but reciprocally (Cot-1 DNA from H. intermedius on chromosomes of H. aimara) displayed signals on at least 4 chromosome pairs. Present findings indicate (i) different composition of repetitive sequences around centromeres, (ii) different NOR phenotypes and (iii) distinct taxonomic status of both giant trahira species.

Twenty Years of Physical Mapping of Major Ribosomal RNA Genes across the Teleosts: A Review of Research

“…The 2 species, H. intermedius and H . aimara, have identical 2n = 50 karyotypes, but 1 and 2 rDNA-bearing chromosome pairs, respectively [Blanco et al, 2011]. In contrast, in H. malabaricus (2n = 40/42), the number of NOR-bearing chromosomes ranges from 4 to 7 [Born and Bertollo, 2000;Cioffi et al, 2009].…”

Karyotypic diversity and chromosome evolution in the armored catfishes Callichthyinae (Siluriformes, Callichthyidae)

“…Physical mapping studies of 5S and 18S rDNA have contributed to the cytotaxonomy and/or cytosystematics of different groups, e.g. Parodontidae (Bellafronte et al 2005), in Gymnotus (Silva et al 2011a), in Ancistrus (Mariotto et al 2011), in Pimelodus (Garcia and Moreira-Filho 2008), in Erythrinus (Blanco et al 2011), and in Loricariidae (Ziemniczak et al 2012).…”

Construction and Characterization of a Repetitive DNA Library in Parodontidae (Actinopterygii: Characiformes): A Genomic and Evolutionary Approach to the Degeneration of the W Sex Chromosome

“…However, reassociation kinetics based on C o t-1 DNA and the microdissection of chromosomes submitted to C-banding and the subsequent amplification of heterochromatic sequences using degenerate oligonucleotide-primed polymerase chain reaction (PCR) have been used successfully. [9][10][11][12][13][14] The Parodontidae is a Neotropical fish group that is divided into three genera: Parodon, Apareiodon, and Saccodon. 15 Cytogenetic studies reported a conserved diploid number of 54 chromosomes in Parodontidae with distinctive karyotype formulae and numerical/position variation of 18S and 5S rDNA sites.…”