Comparative cytogenetics of ten species of cichlid fishes (Teleostei, Cichlidae) from the Araguaia River system, Brazil, by conventional cytogenetic methods

Abstract

Cichlids represent one of the most species-rich families of fishes and have attracted the attention of evolutionary biologists due to the rapid radiation occurring in some groups and the importance of some species in the world aquaculture. Cytogenetic analysis was conducted in 10 cichlid species from the Araguaia River, Amazon Basin, Brazil. The chromosome number was 2n=48 for all analyzed species except for Laetacara araguaiae Ottoni et Costa, 2009 (2n=44). Chromosomal polymorphism was detected only in Geophagus proximus (Castelnau, 1855), which exhibits an extra large submetacentric and and a dot-like chromosomes. Moreover, the C-banding revealed a general pericentromeric heterochromatic pattern and some additional blocks for some species. The heterochromatic blocks corresponding to AgNOR bearing regions were observed in all species and also corresponded to CMA3 positive blocks, which were observed in terminal regions. Besides the general conserved chromosomal and heterochromatin patterns for South American cichlids, the presence of GC-rich heterochromatin was quite different in the species Biotodoma cupido (Heckel, 1840), Geophagus proximus, Retroculus lapidifer (Castelnau, 1855), Crenicichla strigata Günther, 1862 and Heros efasciatus Heckel, 1840. The results suggest that independent events of heterochromatin modification occurred during chromosome evolution in the group, regardless of the conservation of macro-chromosomal structure.

Organization and Distribution of Repetitive DNA Classes in the <i>Cichla kelberi</i> and <i>Cichla piquiti</i> Genome

“…In our results, we observed 2n= 48 chromosomes of subtelocentric/acrocentric type in all specimens analyzed of C. kelberi and C. piquiti (Fig. 1), corroborating previous analyses reported for both species as the modal and fundamental number (Poletto et al 2010, Teixeira et al 2009, Valente et al 2012.…”

“…Since previous studies were performed for the genus Cichla by Poletto et al (2010), Teixeira et al (2009) and Valente et al (2012), these results contribute to the understanding of multigenic family evolution and reinforce classical cytogenetic data previously reported. This increases the knowledge of the chromosomes of this family, which has a wide distribution in Brazilian river basins, and for presenting recent description, work is needed to supplement the various areas of study.…”

“…The Ag-NOR technique revealed the presence of single nucleolar sites in both species reported, located in the terminal region of the second chromosome pair (Fig. 1), a pattern previously observed by Teixeira et al (2009) andValente et al (2012), and later confirmed by FISH with the 18S ribosomal gene in both species (Fig. 1).…”

B chromosome polymorphism in South American cichlid

“…Crenicichla lepidota is a South American cichlid distributed in Argentina, Bolivia, Brazil, and Paraguay, along the basins of Paraná River, Paraguay River, Guaporé River, Uruguay River, and along the coast of Rio Grande do Sul (southern Brazilian state) [10]. An invariant diploid number 2n = 48 has been reported for Crenicichla species [11][12][13][14], with C. lepidota being no exception [9,[15][16][17][18][19][20][21][22][23].…”

First cytogenetic report in Cichlasoma sanctifranciscense Kullander, 1983 (Perciformes, Cichlidae) from northeastern Brazil with inferences on chromosomal evolution of Cichlasomatini

“…Because of their explosive adaptive radiation ( Smith et al 2008 ), comparative cytogenetic studies in cichlids are particularly interesting for inferences on chromosomal evolution and cytotaxonomy. Yet, the number of karyotyped species in Cichlidae is small when compared to the remarkable diversity of this family, comprising only about 8% of described species ( Feldberg et al 2003 , Valente et al 2012 ). Moreover, most karyotypic reports in this fish group include only conventional chromosomal analyses, while detailed information such as mapping of specific genes or regions are restricted to a few species (e.g.…”