Population divergence and peculiar karyoevolutionary trends in the loricariid fish Hypostomus aff. unae from northeastern Brazil

Abstract

ABSTRACT. Loricariidae (Siluriformes, Hypostominae) is one of the most diverse catfish families. In spite of the wide distribution of loricariids in South America, cytogenetic reports are available for only a few species, mostly from southern and southeastern Brazil. We made the first chromosomal analysis of Hypostomus aff. unae from the Contas River basin in northeastern Brazil. Four populations isolated by short distances but from distinct landscapes were studied based on conventional staining, C-banding, argyrophilic nucleolar organizer regions (Ag-NOR), CMA 3 / DAPI fluorochrome staining, and fluorescent in situ hybridization with 18S rDNA probes. Although sharing the same diploid number (2n = 76) and NOR locations, each population presented exclusive karyotype formulae and specific patterns of heterochromatic and AT-rich regions. The derived karyotypes of H. aff. unae (2n >54; high number of acrocentrics bearing AT-rich interstitial heterochromatin) indicated a divergent karyoevolution, mostly driven by centric fissions, pericentric inversions and particular heterochromatin dispersion models. This finding of distinct evolutionary units in H. aff. unae will be useful for understanding the natural history of loricariids from relatively unexplored coastal basins in South America.

Studies in two allopatric populations of Hypostomus affinis (Steindachner, 1877): the role of mapping the ribosomal genes to understand the chromosome evolution of the group

“…Because the presence of a pair of chromosomes carrying the rDNA in fish is thought to be a plesiomorphic condition (Martins and Galetti Jr 1999, Oliveira and Gosztonyi 2000), even for Loricariidae (Kavalco et al 2004a, Alves et al 2012), the genus Hypostomus may contain lines with contrasting tendencies (Pansonato-Alves et al 2013) and possibly an ancestral phenotype with a site in a chromosomal pair (Traldi et al 2013). Dispersion of ribosome cistrons may be related to not only species-specific events but also populational events, as in armored catfish in which the formation of isolated populations typically occurs because of low vagility (Artoni and Bertollo 2001, Bitencourt et al 2012). In fact, variations in the distribution of 18S rDNA sites in the genus Hypostomus were clear, and it was difficult to establish evolutionary tendencies for the character, as observed among different populations of the Paraíba do Sul river.…”

“…Hypostomus is considered one of the most diverse genus of Neotropical fish, and many genetic studies have examined their complex karyotype evolution (Rubert et al 2008, Bitencourt et al 2012, Endo et al 2012, Pansonato-Alves et al 2013, Traldi et al 2013); studies have also been conducted to identify different species and detect phylogenetic relationships within the genus (Montoya-Burgos et al 2002, Armbruster 2004, Lujan et al 2015). …”

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

“…Several cytogenetic studies in Hypostomus revealed a great complexity and diversity of information [10][11][12][13][14][15][16][17][18][40][41][42][43][44][45][46] , showing extensive karyotype variation in this group. Cytogenetic analysis evidenced 2n = 54 chromosomes as an ancestral characteristic in Loricariidae, since it was reported in the basal genera and in the sister group Trichomycteridae 47 .…”

Identification of naturalized goat breeds under conservation from northeastern Brazil using chromosomal markers

“…A remarkable difference in the number of terminal GC-rich sites was detected, since several chromosomes in Moxotó had CMA 3 + signals at their telomeres (Figure 4). Even though this technique has been routinely applied to other vertebrates (Schmid, 1980;Bitencourt et al, 2012), little is known about the distribution of base-specific fluorochrome signals in mammals. As far as we are concerned, there are no reports available about combined CMA 3 /DAPI staining in goat species, which restrains further considerations.…”