Cytogenetic analysis of five species of the subfamily Corydoradinae (Teleostei: Siluriformes: Callichthyidae)

Abstract

In the present study, five callichthyid species belonging to the subfamily Corydoradinae were karyotyped: three species of Aspidoras and two of Corydoras. The three species of Aspidoras had the same diploid number, 2n = 46 chromosomes, similar karyotypic formulae, with most chromosomes metacentric or submetacentric, single interstitial Ag-NORs and C-band positive segments mainly found in the centromeric position. The comparative analysis of cytogenetic data available for the genus Aspidoras and other species of Corydoradinae suggest that several events of centric fusion occurred in the origin of the species of Aspidoras. The two analyzed species of Corydoras showed high diploid numbers, 2n = 74 in C. sodalis and 2n = 90 in C. britskii. While C. sodalis exhibited single Ag-NORs and terminal, interstitial and centromeric C-band positive segments in almost all chromosomes, C. britskii showed multiple Ag-NORs and a small number of C-band positive segments found in the terminal position in one acrocentric (A) pair and in the interstitial position in one subtelocentric (ST) pair. The occurrence of high diploid numbers and many ST and A chromosomes are uncommon among the Corydoradinae, suggesting the occurrence of a high number of chromosome rearrangements, mainly centric fissions, in the origin of the Corydoras species studied.

Hoplosternum littorale (Teleostei, Callichthyidae) from a Coastal River basin in Brazil - Cytogenetic analysis and gene mapping of 5S and 18S rDNA

“…Two heterochromatic regions were GC-rich, as evidenced by chromomycin A 3 staining (Figure 3d), one of them corresponding to Ag-NORs and the other located in an interstitial position on one pair of large acrocentric chromosomes. (Figures 3a and b) seems to be usual in the subfamily Callichthyinae, since it was also observed in Callichthys callichthys (Kavalco and margarido 2001) and Leptoplosternum tordilho (Shimabukuro-Dias et al 2000). These results are in agreement with the plesiomorphic condition of single and terminal NORs suggested for teleosteans (Oliveira and Gosztonyi 2000).…”

“…These diploid number and karyotype formula seem to be common between genera Hoplosternum and Leptoplosternum, two closely related taxa. The studies of Shimabukuro- Dias et al (2000) indicate that L. tordilho presents a karyotype similar to that of H. littorale, including the location of nucleolar organizer regions (NORs) and heterochromatin, as well as of GC-rich regions.…”

An uncommon co-localization of rDNA 5S with major rDNA clusters in Callichthyidae (Siluriformes): a report case in Corydoras carlae Nijssen & Isbrücker, 1983

“…Cytogenetic studies have classified the species of the genus Corydoras into five groups according to their karyotype composition (Oliveira et al 1992, Shimabukuro-Dias et al 2004). Corydoras carlae has been included in group 4 (2n = 40-52 chromosomes, with many metacentric and submetacentric chromosomes).…”

“…Considering aspects related to number and morphology of chromosomes, as well as analysis of DNA content, Oliveira et al (1992) and Shimabukuro-Dias et al (2004) proposed the existence of five groups of species in Corydoras . However, the vast majority of studies in Corydoras is restricted to conventional analysis and little is known about location of the different types of rDNA, only in Corydoras paleatus (Jenyns, 1842) and Corydoras ehrhardti Steindachner, 1910 for 18S rDNA (Artoni et al 2006) and Corydoras britskii (Nijssen & Isbrücker, 1983) for 18S and 5S rDNA (Takagui et al 2014), making essential the development of studies with this approach to better understand the relationships between species of Corydoras .…”

Evolutionary mechanisms of runaway chromosome number change in Agrodiaetus butterflies

“…In vertebrates, the range of chromosome number variation between closely related species is smaller, yet still impressive: in Corydoras fish genus (Siluriformes: Callichthyidae) 35 haploid numbers are ranging from n = 22 to n = 51. South American rodents of the genus Ctenomys (Rodentia: Ctenomiydae) have haploid chromosome numbers varying from n = 5 to n = 35 among the 60 species described 36 , 37 .…”