Chromosomal diversity in Hypostomus (Siluriformes, Loricariidae) with emphasis on physical mapping of 18S and 5S rDNA sites

Abstract

ABSTRACT. We examined chromosomes of three species of the genus Hypostomus, in order to contribute to the understanding of the karyotype evolution of this group. Specimens of H. ancistroides and H. nigromaculatus displayed differences in karyotype formulas, distribution and location of heterochromatin and nucleolus organizer regions when compared to other populations of the same species. We made the first cytogenetic characterization of H. tapijara, an endemic species in the Ribeira de Iguape River. These specimens had 2n = 66 chromosomes, while H. ancistroides showed 2n = 68 and H. nigromaculatus 2n = 76 chromosomes. Physical mapping of 18S and 5S rDNA sites of the three species showed simple, multiple and syntenic clusters. Synteny of ribosomal sites was found in H. ancistroides and H. tapijara, and an interspersed pattern between these sites in all chromosomes bearing the synteny was observed. We conclude that the genus Hypostomus has a high chromosome complexity that is accompanied by great morphological variation. It is evident that this group comprises an interesting model for understanding the chromosome evolution of Neotropical ichthyofauna.

Cytogenetic analysis of Baryancistrus xanthellus (Siluriformes: Loricariidae: Ancistrini), an ornamental fish endemic to the Xingu River, Brazil

“…In Loricariidae, chromosomes with syntenic markings of the 18S and 5S rDNA were observed in species of Neoplecostominae, Hypoptopomatinae (Ziemniczak et al, 2012), Loricariinae (Kavalco et al, 2004), Hypostominae (Ancistrini and Hypostomini) (Mariotto et al, 2011;Traldi et al, 2013) and in the outgroup, Trichomycteridae family (Ziemniczak, 2011). Based on this data, Ziemniczak (2011) inferred that the synteny of these classes of rDNA is a plesiomorphic character in the family.…”

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

“…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). …”

“…This marker has been defined in only approximately a dozen species of the genus for some Neotropical populations (Kavalco et al 2004a, Mendes-Neto et al 2011, Traldi et al 2012, Pansonato-Alves et al 2013, Traldi et al 2013, Baumgärtner et al 2014, Bueno et al 2014, Rocha-Reis et al unpublished data). Similar results were observed for the distribution of constitutive heterochromatin, although this type of highly compacted DNA requires further examination.…”

The Persevering Cytotaxonomy: Discovery of a Unique XX/XY Sex Chromosome System in Catfishes Suggests the Existence of a New, Endemic and Rare Species

“…Loricariids generally have little constitutive heterochromatin [Mariotto et al, 2009], as described previously for some H. ancistroides populations [Artoni and Bertollo, 1996;Rubert et al, 2011;Traldi et al, 2013]. Accordingly, faint heterochromatin blocks were detected in the pericentromeric and terminal regions of some chromosome pairs of H. aff.…”

“…ancistroides ( Fig. 3 , 4 ), multiple sites were found in H. ancistroides from the Corrego Lapa (Paraná River basin) [Traldi et al, 2013]. Variation in the number and position among different populations of the same species suggests that 5S rDNA may represent a useful population marker .…”