Karyotype structure of Hypostomus cf. plecostomus (Linnaeus, 1758) from Tapajós River basin, Southern Amazon: occurrence of sex chromosomes (ZZ/ZW) and their evolutionary implications

Abstract

ABSTRACT.Hypostomus is a group of fish with numerical and structural karyotypic variability. Among them, only six species, three of which belong to the Amazon basin, show a sex chromosome. In this study, we present the karyotype structure of Hypostomus cf. plecostomus from the Teles Pires river basin in the municipality of Alta Floresta, MT. The species has 2n = 68 and the karyotype formula 14m+ 24sm+ 14st+ 16a [fundamental number (FN) = 120] in males and 15m+ L.C. Oliveira et al. 6626©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (2): 6625-6634 (2015) 24sm+14st+15a (FN = 121) in females and sex chromosomes ZZ/ZW. Argyrophilic nucleolar organizer regions (AgNORs) were identified in two pairs of chromosomes at different positions: short arm of the pair 21and long arm of the pair 27, matching the signals displayed by 18S FISH and indicating multiple NORs. Analysis of band C detected few blocks of constitutive heterochromatin in the pericentromeric regions of most chromosomes and the telomeric regions of some pairs, including the nucleolar pair 21. However, large blocks on the long arm of the nucleolar pair 27 still stood out. GC-rich heterochromatin (CMA 3 ) was visualized only coincidently with nucleolar sites. Mapping of 5S rDNA sites with FISH revealed markings in eight chromosomes, demonstrating synteny between the 18S and 5S sites. The data obtained for H. cf. plecostomus are important for taxonomic studies of this Amazon complex "H. plecostomus group". The occurrence of sex chromosomes in Amazon species of Hypostomus suggests an evolutionary event that is independent of other species in the group.

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

“…The rRNA in eukaryotes presents as two subunits (one formed by 28S, 18S and 5.8S and another one formed by 5S) and their DNA sequences vary very slowly due to selective pressure, being considered highly conserved (Long and Dawid 1980). This allows the interspecific hybridization of the mentioned probes (obtained from Prochilodus argenteus and Megaleporinus elongatus ), with chromosomes of a wide variety of fishes, like Characiformes (de Marco Ferro et al 2001, Pazza et al 2006, da Silva et al 2016), Gymnotiformes (Fernandes et al 2017a, 2017b) Perciformes (Jacobina et al 2014, Argôlo and Affonso 2015, Oliveira et al 2015b), Siluriformes (Blanco et al 2014, Kantek et al 2015, Ribeiro et al 2015), including other species of Hypostomus (Kavalco et al 2004a, 2005, Traldi et al 2013, Baumgärtner et al 2014, Oliveira et al 2015a, Lara Kamei et al 2017). …”

“…Loricariidae exhibits large variations in diploid number, ranging from 2n = 36 chromosomes in Loricaria latirostris Boulenger, 1900 (Giuliano-Caetano 1998) to 2n = 96 in Hemipsilichthys gobio Lütken, 1874 (Kavalco et al 2005, previously identified as Upsilodus sp.). This group shows several structural differences (Mariotto et al 2009), numerous polymorphisms (Giuliano-Caetano 1998, Cereali et al 2008), and morphologically differentiated sex chromosome systems (Alves et al 2006, Oliveira et al 2007, Konerat et al 2015, Oliveira et al 2015a, Rocha-Reis et al unpublished data), which nearly always correspond to unique chromosomal features.…”

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

“…The presence of extensive heterochromatic blocks on only one chromosomal arm is an intriguing trait of the chromosome morphology found in some Hypostomus species. Heterochromatinization processes and/or an amplification of this region were suggested as an attempt to explain the heterochromatic chromosomal polymorphism in a population of Hypostomusiheringii Regan, 1908 (Traldi et al 2012), in H.strigaticeps (Baumgärtner et al 2014) and Hypostomuspropeplecostomus Linnaeus, 1758 (Oliveira et al 2015). Furthermore, the presence of transposable elements (TEs) has been confirmed in the heterochromatic regions of a number of fish species (Ferreira et al 2011), including two Hypostomus species (Pansonato-Alves et al 2013), which could explain the origin of the heteromorphic metacentric in H.regani .…”

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

“…Hypostomus plecostomus (Linnaeus, 1758) was described with 2n = 54 chromosomes 48 . However, it was considered a misidentification case, once the recent cytogenetic studies in this species has demonstrated 2n = 68 chromosomes 49 [11][12][13]50 . The chromosomal data in this study showed that 2n = 68 and different karyotype formulae between H. commersoni and H. derbyi could be explained by pericentric inversions.…”