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

Abstract

Anostomidae are a neotropical fish family rich in number of species. Cytogenetically, they show a conserved karyotype with 2n = 54 chromosomes, although they present intraspecific/interspecific variations in the number and chromosomal location of repetitive DNA sequences. The aim of the present study was to perform a comparative description of the karyotypes of two populations of Leporinusfriderici Bloch, 1794 and three populations of Leporellusvittatus Valenciennes, 1850. We used conventional cytogenetic techniques allied to fluorescence in situ hybridization, using 18S ribosomal DNA (rDNA) and 5S rDNA, a general telomere sequence for vertebrates (TTAGGG)n and retrotransposon (RTE) Rex1 probes. The anostomids in all studied populations presented 2n = 54 chromosomes, with a chromosome formula of 32m + 22sm for L.friderici and 28m + 26sm for L.vittatus. Variations in the number and location of the 5S and 18S rDNA chromosomal sites were observed between L.friderici and L.vittatus populations and species. Accumulation of Rex1 was observed in the terminal region of most chromosomes in all populations, and telomere sequences were located just on all ends of the 54 chromosomes in all populations. The intraspecific and intergeneric chromosomal changes occurred in karyotype differentiation, indicating that minor chromosomal rearrangements had present in anostomid species diversification.

Karyotype variability in six Amazonian species of the family Curimatidae (Characiformes) revealed by repetitive sequence mapping

“…Interestingly, Curimatella dorsalis seems to be the first case to show synteny between these rDNAs in curimatids, which may have arisen independently during non-Robertsonian rearrangements ( Symonová et al, 2013 ), demonstrating the dynamic nature of the 18S and 5S rDNA sites, prone to recombination events. Synteny between 18S and 5S rDNA is an atypical situation, including for the superfamily Anostomoidea (Anostomidae, Chilodontidae, Prochilodontidae and Curimatidae), which has been reported only in lineages derived of the Anostomidae ( De Barros et al, 2017 ; Dulz et al, 2019 ), Prochilodontidae ( Vicari et al, 2006 ; Terencio et al., 2012 ; Voltolin et al, 2013 ) and Curimatidae families (present study).…”

Cytogenetic analysis of Hypomasticus copelandii and H. steindachneri: relevance of cytotaxonomic markers in the Anostomidae family (Characiformes)

“…Barros et al (2017) acknowledged that this discrepancy observed on these three species could be due to technical artifacts and suggested that the expansion of the 18S rDNA sites in Anostomidae should be verified with supplementary analysis. The 18S and 5S rDNA probes were not co-located in neither H. copelandii nor H. steindachneri, as observed in most species of the family (Table 1), although it remains to be confirmed with double-FISH analysis, as syntenic sites have been observed in other species of the family, such as in Megaleporinus trifasciatus (Steindachner, 1876), Laemolyta taeniata (Kner, 1858), Schizodon fasciatus Spix et Agassiz, 1829 (Barros et al 2017), and Leporellus vittatus (Valenciennes, 1850) (Dulz et al 2019).…”