Cytogenetic analysis of the 18S, 5S rDNA and B chromosome of Iheringichthys labrosus (Lütken, 1874) (Siluriformes, Pimelodidae)

Abstract

Cytogenetic analyses of the location of 18S and 5S ribosomal DNAs, and the base composition of B chromosomes of Iheringichthys labrosus from Tibagi River, Paraná, Brazil, are provided. AgNORs were observed in the terminal position on the long arm of a subtelocentric chromosome pair. CMA 3 -positive staining was observed in some chromosomes, which besides being associated with NORs, were all DAPI-negative. Chromosome B showed a strong fluorescence with CMA 3. The concomitant use of 18S and 5S rDNA probes using the FISH technique revealed 18S ribosomal cistrons in a pair of subtelocentric chromosomes, on the long arm in the terminal position, coinciding with the AgNOR. The 5S sites were found in another subtelocentric pair, on the long arm in the interstitial region, near the centromere. The findings of the present study suggest that, although there are some more conserved cytogenetic characteristics, populations of I. labrosus may show their own characteristics.Keywords: supernumerary chromosome, catfish, FISH. Análise Citogenética de DNAr 18S, 5S e cromossomo B deIheringichthys labrosus (Lütken, 1874) (Siluriformes, Pimelodidae) ResumoForam realizadas análises citogenéticas em Iheringichthys labrosus do Rio Tibagi, Paraná, Brasil com a localização cromossômica dos DNAs ribossômicos 18S e 5S e a composição de bases de seus cromossomos B. As AgNORs foram observadas em posição terminal, no braço longo de um par de cromossomos subtelocêntricos. Marcações CMA 3 positivas foram observadas em alguns cromossomos e associadas com as RONs. Porém, todas estas marcações apresentaram-se DAPI negativas. O cromossomo B mostrou-se fortemente fluorescente com CMA 3 . O uso concomitante das sondas de DNAr 18S e 5S, através da técnica de FISH, revelou os cístrons ribossômicos em um par de cromossomos subtelocêntricos, em posição terminal do braço longo, coincidindo com a AgNOR. Os sítios 5S foram observados em outro par subtelocêntrico, em posição intersticial do braço longo, próximo ao centrômero. Os resultados observados no presente estudo sugerem que, embora existam algumas características citogenéticas mais conservadas, as populações de I. labrosus podem mostrar suas próprias características.Palavras-chave: cromossomo supranumerário, catfish, FISH.

Cytogenetic characterization of F1, F2 and backcross hybrids of the Neotropical catfish species Pseudoplatystoma corruscans and Pseudoplatystoma reticulatum (Pimelodidae, Siluriformes)

“…FISH revealed 18S rDNA clusters in the regions corresponding to NORs in both P. corruscans and P. reticulatum, thus confirming the existence of only one chromosome pair bearing this gene, as is usually the case in the Pimelodidae (Vasconcelos and Martins-Santos, 2000; Swarça et al , 2008; Carvalho et al , 2010). Regardless of the Ag-NOR variation, in situ hybridization in the F1 and F2 hybrids indicated that the 18S ribosomal genes were not lost or altered, as also reported for hybrids of Leporinus (Hashimoto et al , 2009).…”

“…Although few chromosomal mapping studies have examined the 5S gene in the Pimelodidae, the evidence indicates the prevalence of only two chromosomes related to these ribosomal sites (Swarça et al , 2009; Carvalho et al , 2010). As shown here, the 5S ribosomal gene was located pericentromerically on one chromosomal pair in P. reticulatum and P. corruscans , as also observed by Swarça et al (2005) and Neto et al (2011); the hybrid lineages showed 5S demarcations at the same chromosomal positions as their parental lineages, thus conforming previous observations for this fish group.…”

Chromosomal Mapping of Repeat DNA in <b><i>Bergiaria westermanni</i></b> (Pimelodidae, Siluriformes): Localization of 45S rDNA in B Chromosomes

“…Heterochromatic B chromosomes, as visualized in B. westermanni , have already been reported in karyotypes of other species of Pimelodidae [Borin and Martins-Santos, 2004;Carvalho and Dias, 2005]. The presence of only 1 NOR-bearing chromosome pair is the most common condition among the pimelodids [Borin and Martins-Santos, 2002;Treco and Dias, 2009;Carvalho et al, 2010;Swarça et al, 2013], and the correspondence between CDD sites and NORs, observed in this study, has already been found in the genomes of other species of this family [Garcia and Moreira Filho, 2005;Swarça et al, 2005Swarça et al, , 2013Treco et al, 2008;Carvalho et al, 2011]. The location of (TTAGGG) n sites only in telomeric regions indicated the complete lack or a small number of chromosomal rearrangements of translocation/fusion types.…”

“…Characterization and localization of repetitive sequences have rarely been performed in representatives of the Pimelodidae and have been limited to the physical mapping of 18S and 5S rDNA sites in chromosomes [Garcia and Moreira-Filho, 2008;Carvalho et al, 2010]. In this context, the present study employed chromosome mapping of repetitive sequences in chromosomes of Bergiaria westermanni , focusing on the presence or absence of rDNAs, small nuclear RNAs (snRNAs), histones, and (TTAGGG) n and (GATA) n sites in the B chromosomes.…”

Cytogenetic studies in the redtail catfish, Phractocephalus hemioliopterus (Bloch &amp; Schneider, 1801) (Siluriformes, Pimelodidae) a giant fish from Amazon basin

“…2c, d). In general, the 18S and 5S rDNA sites are not syntenic but located on different chromosome pairs, this feature being the most frequent patter in several Pimelodidae species (Carvalho et al 2010, Swarça et al 2008, 2009). However, recently syntenic localization of the major rDNA clusters and the 5S sites were reported in other species (Ziemniczak et al 2012, Konerat et al 2014, da Rocha et al 2016).…”