Cytogenetic characterization and description of an XX/XY₁Y₂ sex chromosome system in catfish <i>Harttia carvalhoi</i> (Siluriformes, Loricariidae)

Abstract

Karyotypic and cytogenetic characteristics of catfish Harttia carvalhoi (Paraíba do Sul River basin, São Paulo State, Brazil) were investigated using differential staining techniques (C-banding, Ag-staining) and fluorescent in situ hybridization (FISH) with 18S and 5S rDNA probes. The diploid chromosome number of females was 2n = 52 and their karyotype was composed of nine pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric and four pairs of acrocentric chromosomes. The diploid chromosome number of males was invariably 2n = 53 and their karyotype consisted of one large unpaired metacentric, eight pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric, four pairs of acrocentric plus two middle-sized acrocentric chromosomes. The differences between female and male karyotypes indicated the presence of a sex chromosome system of XX/XY₁Y₂ type, where the X is the largest metacentric and Y₁ and Y₂ are the two additional middle-sized acrocentric chromosomes of the male karyotype. The major rDNA sites as revealed by FISH with an 18S rDNA probe were located in the pericentromeric region of the largest pair of acrocentric chromosomes. FISH with a 5S rDNA probe revealed two sites: an interstitial site located in the largest pair of acrocentric chromosomes, and a pericentromeric site in a smaller metacentric pair of chromosomes. Translocations or centric fusions in the ancestral 2n = 54 karyotype is hypothesized for the origin of such multiple sex chromosome systems where females are fixed translocation homozygotes whereas males are fixed translocation heterozygotes. The available cytogenetic data for representatives of the genus Harttia examined so far indicate large kayotype diversity.

Diversity and chromosomal evolution in the genus Ancistrus Kner, 1854 (Loricariidae: Ancistrini) from three hydrographic basins of Mato Grosso State, Brazil

“…M: males, F: females. Loricariichthys (Scavone & Júlio Jr., 1995), Hemiancistrus (de and Harttia (Centofante et al, 2006). However, in the present study, the species located at higher altitude differed from those located in lower places and/or regions with high sediment flow.…”

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

“…In Siluriformes, the mapping of the ribosomal genes 18S and 5S is still very incipient (Kavalco et al, 2004;Centofante et al, 2006;Mendes-Neto et al, 2011). 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).…”

Occurrence of multiple sexual chromosomes (XX/XY1Y2 and Z1Z1Z2Z2/Z1Z2W1W2) in catfishes of the genus Ancistrus (Siluriformes: Loricariidae) from the Amazon basin

“…Thus far, 63 occurrences of heteromorphic sex chromosomes have been described for this group of fish. Sixty-three and a half percent of these represent cases in which females are heterogametic, 36.5% in which males are heterogametic, and 19% are cases of multiple systems (Centofante et al 2002;Mariotto et al 2004;Venere et al 2004;Alves et al 2006;Centofante et al 2006;de Oliveira et al 2006;Mariotto and Miyazawa 2006).…”

“…In the subfamily Hypostominae, XX/XY (Michelle et al 1977;Mariotto and Miyazawa 2006), XX/XO (Alves et al 2006), and ZZ/ZW (Artoni et al 1998;Mariotto et al 2004;de Oliveira et al 2006) sex chromosome systems have been found. XX/XY (Andreata et al 1992) and ZZ/ ZW (Andreata et al 1993;1994) systems have been described for species of Hypoptopomatinae, and ZZ/ZW (Scavone and Júlio Jr. 1995) and XX/XY 1 Y 2 (Centofante et al 2006) systems have been described for Loricariinae.…”