Abstract
Fish of the family Cichlidae are recognized as an excellent model for evolutionary studies because of their morphological and behavioral adaptations to a wide diversity of explored ecological niches. In addition, the family has a dynamic genome with variable structure, composition and karyotype organization. Microsatellites represent the most dynamic genomic component and a better understanding of their organization may help clarify the role of repetitive DNA elements in the mechanisms of chromosomal evolution. Thus, in this study, microsatellite sequences were mapped in the chromosomes of Cichla monoculus Agassiz, 1831, Pterophyllum scalare Schultze, 1823, and Symphysodon discus Heckel, 1840. Four microsatellites demonstrated positive results in the genome of Cichla monoculus and Symphysodon discus, and five demonstrated positive results in the genome of Pterophyllum scalare. In most cases, the microsatellite was dispersed in the chromosome with conspicuous markings in the centromeric or telomeric regions, which suggests that sequences contribute to chromosome structure and may have played a role in the evolution of this fish family. The comparative genome mapping data presented here provide novel information on the structure and organization of the repetitive DNA region of the cichlid genome and contribute to a better understanding of this fish family’s genome.
Highlights
The fish family Cichlidae exhibits high species richness with approximately 3,000 species distributed in Central and South America, Africa, and South India (Kullander 1998, Kocher 2004)
The evolution of this family is characterized by repeated adaptive radiation and sympatric speciation (Schliewen et al 1994, Seehausen 2006). These fish are considered to be an excellent model for evolutionary studies because of their morphological and behavioral adaptations to a wide diversity of explored ecological niches (Lowe-McConnell 1991)
In this fish family, repetitive DNAs, such as transposable elements, co-localize or are associated with ribosomal DNAs, which suggests their roles in the duplication and dispersion of repetitive rDNA sequences (Gross et al 2010, Schneider et al 2013a, Schneider et al 2013b, Nakajima et al 2012)
Summary
The fish family Cichlidae exhibits high species richness with approximately 3,000 species distributed in Central and South America, Africa, and South India (Kullander 1998, Kocher 2004). The species of this family exhibit a dynamic genome with variations in structure and karyotype composition and organization, as demonstrated by the DNA sequencing and the physical chromosome mapping of several repetitive DNA sequences, such as telomere sequences; retrotransposons isolated from Xiphophorus maculatus Günther, 1866 (Rex, Rex, Rex6); retrotransposon isolated from Astronotus ocellatus Agassiz, 1831 similar to Rex (AoRex3); long interspersed elements isolated from Astronotus ocellatus (AoLINE); retrotransposon isolated from Cichla kelberi Kullander & Ferreira, 2006 (RCk); transposon isolated from Caenorhabditis elegans Maupas, 1900 (Tc1); the 18S and 5S ribosomal gene sequences; and U1 spliceosomal small nuclear RNA (U1 snRNAs) (Vicari et al 2006, Gross et al 2009, Mazzuchelli and Martins 2009, Teixeira et al 2009, Gross et al 2010, Poletto et al 2010, Cabral-de-Mello et al 2012, Valente et al 2011, Schneider et al 2013a, Schneider et al 2013b). In this fish family, repetitive DNAs, such as transposable elements, co-localize or are associated with ribosomal DNAs, which suggests their roles in the duplication and dispersion of repetitive rDNA sequences (Gross et al 2010, Schneider et al 2013a, Schneider et al 2013b, Nakajima et al 2012)
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