Abstract
Even though genetic aspects of some cichlids have been widely studied over the last decades, little is known about the genomic structure of Cichlidae when compared to the large number of species in the family. In this paper, the first chromosomal data for Cichlasoma sanctifranciscense Kullander, 1983 are presented and discussed based on cytotaxonomic and karyoevolutionary inferences on Cichlasomatini. All individuals shared a diploid number of 2n=48 distributed as 10sm+28st+10a and Ag-NORs on short arms of a submetacentric pair. Heterochromatin was detected at pericentromeric regions of most chromosomes and at terminal sites of a few pairs. GC-rich regions were observed on short arms of two biarmed pairs, including the pair bearing Ag-NORs. Double-FISH with ribosomal probes revealed 18S rDNA clusters coincident with GC-rich regions in two biarmed pairs and 5S rDNA at interstitial location of an acrocentric pair. Cichlasoma sanctifranciscense shares some symplesiomorphic traits described in Cichlidae (2n=48 and pericentromeric C-bands) while other chromosomal features diverge from the common trend reported in Cichlasomatini, such as multiple 18S rDNA sites combined with high FN values. Finally, the present results are useful to support taxonomic identification once species-specific markers have been provided in Cichlasoma sanctifranciscense.
Highlights
Cichlids are one of the largest families within vertebrates, including more than 1600 species (Froese and Pauly 2015) and have been regarded as model organisms for evolutionary, genetic and ecological studies
GC-rich regions, i.e. repetitive sequences positively stained by chromomycin A3 (CMA3) and negatively stained by DAPI, were identified at terminal regions on short arms of four chromosomes, including the sm pair bearing active NORs and a st pair (Fig. 2d)
The modal number (2n=48) in C. sanctifranciscense follows the plesiomorphic pattern reported in the majority of studied cichlids (Feldberg et al 2003), suggesting a conservative chromosomal evolution in relation to diploid values (Affonso and Galetti 2005)
Summary
Cichlids are one of the largest families within vertebrates, including more than 1600 species (Froese and Pauly 2015) and have been regarded as model organisms for evolutionary, genetic and ecological studies. In the Neotropical region, this group is represented exclusively by the monophyletic subfamily Cichlinae that stands out as the third most predominant group of freshwater fish (Reis et al 2003). Because of their explosive adaptive radiation (Smith et al 2008), comparative cytogenetic studies in cichlids are interesting for inferences on chromosomal evolution and cytotaxonomy. 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 Cichlids with highly divergent karyotypes have been recently reported in this family, like that observed in genus Symphysodon Heckel, 1840 whose species are characterized by 2n=60, several biarmed chromosomes and meiotic chains (Gross et al 2009, 2010)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
