Chromosomal Mapping of Repetitive DNA Sequences in the Genus Bryconamericus (Characidae) and DNA Barcoding to Differentiate Populations

Abstract

The mapping of repetitive DNA sites by fluorescence in situ hybridization has been widely used for karyotype studies in different species of fish, especially when dealing with related species or even genera presenting high chromosome variability. This study analyzed three populations of Bryconamericus, with diploid number preserved, but with different karyotype formulae. Bryconamericus ecai, from the Forquetinha river/RS, presented three new cytotypes, increasing the number of karyotype forms to seven in this population. Other two populations of Bryconamericus sp. from the Vermelho stream/PR and Cambuta river/PR exhibited interpopulation variation. The chromosome mapping of rDNA sites revealed unique markings among the three populations, showing inter- and intrapopulation variability located in the terminal region. The molecular analysis using DNA barcoding complementing the cytogenetic analysis also showed differentiation among the three populations. The U2 small nuclear DNA repetitive sequence exhibited conserved features, being located in the interstitial region of a single chromosome pair. This is the first report on its occurrence in the genus Bryconamericus. Data obtained revealed a karyotype variability already assigned to the genus, along with polymorphism of ribosomal sites, demonstrating that this group of fish can be undergoing a divergent evolutionary process, constituting a substantive model for studies of chromosomal evolution.

Conserved number of U2 snDNA sites in Piabina argentea, Piabarchus stramineus and two Bryconamericus species (Characidae, Stevardiinae)

“…In two Bryconamericus species, Piabarchus stramineus and Piabina argentea under study, as well as shown by Santos et al (2017), the U2 snDNA clusters were observed on the interstitial/pericentromeric regions of the long arm of one chromosome pair in all species, except fo Bryconamericus sp. (Cambuta River) that showed one pair bearing U2 snDNA clusters in interstitial position on the short arm.…”

“…To date, only studies in B. ecai da Silva, 2004 and Bryconamericus sp. showed chromosomal mapping of U2 snDNA in this fish group (Santos et al, 2017). The chromosomal mapping of U2 snDNA clusters Repetitive DNA in Piabina,Piabarchus and Bryconamericus Neotropical Ichthyology,16( showed a broad scenario in fish chromosomes, with these sequences accumulating in one or more chromosome pairs.…”

“…In B. ecai, Bryconamericus sp. (Santos et al, 2017), Astyanax mexicanus (De Filippi, 1853) and A. jordani (Hubbs & Innes, 1936) (Silva et al, 2015) signals in one chromosome pair were detected.…”

Cytogenetic markers as tools in delimiting species of the highly diverse Neotropical fish Bryconamericus (Characiformes: Characidae)

“…(Santos et al, 2017, Cambutá River), and multiple cistrons with intraspecific variation in B. turiuba (Piscor et al, 2013), B. ecai and Bryconamericus sp. (Vermelho stream) (Santos et al, 2017), being that in some cytotypes these genes presented syntenic to 18S rDNA genes.…”

“…Cytogenetic studies in trans-Andean Bryconamericus species evidenced the maintenance of the diploid number of 52 chromosomes, with inter and intraspecific divergences regarding the karyotype formula and the fundamental number (FN) (Paintner-Marques et al, 2002a, 2002bCapistano et al, 2008;Portela-Castro et al, 2008;among others). Likewise, other cytogenetic characters were shown to be variable, such as the distribution of heterochromatin and the number and location of the nucleolar organizer regions (NORs) (Eberhardt et al, 2012;Santos et al, 2012Santos et al, , 2017Silva et al, 2014), with variation even among individuals of the same population. In relation to 5S rDNA ribosomal genes, the data are restricted to only four species, revealing simple cistrons in B. cf.…”