Constitutive heterochromatin heteromorphism in the Neotropical armored catfish Hypostomus regani (Ihering, 1905) (Loricariidae, Hypostominae) from the Paraguay River basin (Mato Grosso do Sul, Brazil)

Abstract

A cytogenetic analysis based on the integration of a number of different chromosomal methodologies, including chromosome microdissection was carried out to characterize the chromosomally polymorphic Hypostomusregani population from the Paraguay River basin, state of Mato Grosso do Sul in Brazil. All specimens had 2n=72 (FN=116) but two distinct karyotype formulas: karyomorph A (12m+14sm+18s+28a) and karyomorph B (13m+14sm+17st+28a). Karyomorph A and B differed only for pair 19 that consisted of two subtelocentrics in karyomorph A and a large metacentric and a subtelocentric in karyomorph B. This heteromorphism was due to extensive heterochromatinization of the short arm of the large metacentric, as highlighted by C-banding. The microdissection of the large metacentric of pair 19 allowed the production of a probe, named HrV (Hypostomusregani Variant), that hybridized to the whole p arm of the large metacentric and the pericentromeric region of the short arm of its (subtelocentric) homologue (karyomorph B) and of both homologs of pair 19 in karyomorph A. Additional cytogenetic techniques (FISH with 18S and 5S rDNA probes, CMA3 and DAPI staining) allowed a finer distinction of the two karyomorphs. These results reinforced the hypothesis that the novel large metacentric of H.regani (karyomorph B) was the result of the amplification of heterochromatin segments, which contributed to karyotypic diversification in this species.

Cytogenetic Analysis of the Members of the Snake Genera Cylindrophis, Eryx, Python, and Tropidophis

“…Polymorphism in the distribution of heterochromatin was found in all tested individuals of E. colubrinus and in two out of six studied individuals of E. miliaris . Heterochromatin heteromorphism was previously described in numerous species of vertebrates [ 49 , 50 , 51 , 52 , 53 ]. Notably, in several species of newt of the genus Triturus , all individuals are heterozygous in certain chromatin blocks, as homozygosity in them is lethal [ 54 ].…”

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

“…A number of cytogenetic studies have examined various aspects of the differentiation of the Hypostomus karyotype, including complex karyotype evolution (Martinez et al 2011; Alves et al 2012; Pansonato-Alves et al 2013; Bueno et al 2014), heterochromatin polymorphism (Traldi et al 2012; Baumgärtner et al 2014), inter-individual chromosome polymorphism (Artoni and Bertollo 1999; Ferreira et al 2019), and morphologically differentiated sex chromosomes (Artoni et al 1998; Oliveira et al 2015; Kamei et al 2017). A range of sex chromosome systems found in 705 fish species are available in the Tree of Sex Consortium (2014) database.…”