Comparative Cytogenetics Among Three Sympatric Hypostomus Species (Siluriformes: Loricariidae): An Evolutionary Analysis in a High Endemic Region

Abstract

The karyotypes of three armored catfish species (Loricariidae) from the Iguaçu river, southern of the Brazil, were compared using different techniques: C-banding, Ag-NOR and fluorescence in situ hybridization (FISH), which used 5S and 18S rDNAs and total Cot-1 fraction as probes. Hypostomus commersoni and Hypostomus derbyi presented 2n = 68 chromosomes, with karyotype formulae 12m+12sm+14st+30a and 12m+12sm+10st+34a, respectively; whereas Hypostomus myersi presented 2n = 74 chromosomes and 12m+16sm+12st+34a. The chromosomal localization of the Ag-NORs, 5S and 18S rDNAs differed in number of sites and chromosomal localization among the studied species. The total Cot-1 probe permitted the visualization of the repetitive DNA fraction in karyotypes of each species. Crosshybridizations using total Cot-1 probe revealed that these species have repetitive DNAs in common. However, this does not occur in H. commersoni in relation to the other species. The apparent karyotype similarity suggests a close relationship between the sympatric H. commersoni and H. derbyi species, but the small differences detected in the examined chromosomal markers indicate evolutionary divergence due to gene flow restriction among them. Hence, the present findings indicate different composition of repetitive sequences among studied species, which permit to infer its role in chromosomal differentiation of Hypostomus.

Cytogenetic characterization of Hypostomus soniae Hollanda-Carvalho & Weber, 2004 from the Teles Pires River, southern Amazon basin: evidence of an early stage of an XX/XY sex chromosome system

“…In Hypostomus , several cases of chromosomal polymorphism associated with the amplification of the heterochromatin, with or without ribosomal genes, have been reported (Artoni and Bertollo 1999; Traldi et al 2012; Baumgärtner et al 2014; Lorscheider et al 2018), but in none of these cases was the polymorphism found in only one of the sexes. In the present paper, all the H. soniae individuals analyzed had the same karyotype structures, although differences were found between the sexes in pair No.…”

Composition and Nature of Heterochromatin in the Electrical Fish (Knifefishes) Gymnotus (Gymnotiformes: Gymnotidae)

“…The prospection of repetitive sequences by the technique of DNA reassociation kinetics (C0t-1) proves to be a safe and fast technique for obtaining copies of highly and moderately repetitive DNA sequences [45]. Thus, it is possible to build libraries and screening repetitive DNAs, and has been used to isolate the highly repeated fraction of the plant genome [46] and animals [47] to significantly expand our knowledge of the organization of their chromosomes.…”

Comparative cytogenetics among Leporinus friderici and Leporellus vittatus populations (Characiformes, Anostomidae): focus on repetitive DNA elements

“…Satellite DNA and TEs are responsible for a large part of the structural and functional organization of genomes (Sumner 2003, Feschotte 2008), and carry sequences containing DNA double-strand break hotspots, resulting in chromosome/genome reshuffle (Eichler and Sankoff 2003, Longo et al 2009, Farré et al 2011, Barros et al 2017a, Glugoski et al 2018). The movement of repetitive sequences within the genome promotes chromosomal differentiation, which has an important role on karyotype evolution (Wichman et al 1991, Pucci et al 2016, 2018a, 2018b, Lorscheider et al 2018, do Nascimento et al 2018).…”