Karyoevolution ofCrenicichlaheckel 1840 (Cichlidae, Perciformes): a process mediated by inversions

Abstract

Crenicichla (Cichliformes, Cichlidae) present a highly conserved diploid number 2n=48 with fundamental numbers varying between 52 and 62. We analyzed four species in order to investigate the role of repetitive DNA in chromosome evolution in the genus. Crenicichla johanna , Crenicichla cf. saxatilis and Crenicichla cf. regani have 2n=48 (8 m/sm and 40st/a) and FN=56, while Crenicichla sp. ‘Xingu I’ has 2n=48 (48 st/a) and FN=48. Different patterns of constitutive heterochromatin distribution were observed including pericentric, interstitial and whole arm C bands. A single chromosome bears 18S rDNA clusters in most species, except C. johanna , where population variation exists in terms of the quantity and distribution of clusters and their association with interstitial telomeric sequences. All species showed hybridization of 5S rDNA sequences in an interstitial region on an acrocentric chromosome pair. The karyotypic differences and maintenance of the diploid number supports chromosome evolution mediated by inversions in Crenicichla . The telomeric and 18S rDNA sequence association in various chromosomes of C. johanna are proposed to represent hotspots for breakage, favoring intra-chromosomal rearrangements. The results suggest that repetitive sequences can contribute to microstructural cytogenetic diversity in Crenicichla .

High Chromosomal Reorganization and Presence of Microchromosomes in Chactidae Scorpions from the Brazilian Amazon

“…Furthermore, in the larger homolog of this pair, an extra site at the opposite end was recorded. This result can be explained by the amplification of 45S rDNA motifs, with subsequent uneven crossing-over between them, similar to that observed in fish [ 41 ], amphibians [ 42 ], plants [ 43 ] and other arthropods [ 15 , 44 ]. The amplification of 45S rDNA is a phenomenon epigenetically controlled by the cell and may constitute a response to environmental factors [ 45 ].…”

“…The amplification of 45S rDNA is a phenomenon epigenetically controlled by the cell and may constitute a response to environmental factors [ 45 ]. In some organisms, such as plants [ 46 ], mammals [ 47 ] and fish [ 41 ], it has been demonstrated that 45S rDNA constrictions constitute sites prone to breakage and can promote genomic instability. During the meiotic bouquet, the chromosome ends and joins the nuclear membrane, and the telomeres remain clustered at a single pole of the cell.…”

Evolutionary insights in Amazonian turtles (Testudines, Podocnemididae): co-location of 5S rDNA and U2 snRNA and wide distribution of Tc1/Mariner

“…Due to its conserved character, the 5S rDNA has been widely used as a marker in molecular cytogenetics for the characterization of various species. Most of the investigated karyotypes have relatively few (often just one) 5S rDNA loci (Sochorová et al, 2018;Frade et al, 2019). The 5S rDNA has been reported to co-localize with other multigenes, such as histones genes and small nuclear RNAs (snRNAs) of the U family (Novotná et al 2011;Piscor et al, 2018); these associations seem to indicate an old and linked organization of such sequences in the genomes of the relevant species (Cabral-de- Mello et al, 2011).…”