Trends in chromosome evolution in Crenicichlina (Cichliformes, Cichlidae, Cichlinae): a new perspective based on the recent classification of the pike cichlids

Comprising more than 100 species, Crenicichlina encompasses 20% of the taxonomic diversity of Neotropical cichlids and is widely distributed throughout Brazilian watersheds. A new hypothesis about the phylogeny of pike cichlids has recently been proposed, based on morphological and molecular characters, and new genera were created. We analyzed 18 species of four genera of Crenicichlina, collected in the Amazon, Iguaçu, Paraná and Uruguay River basins, using conventional and molecular cytogenetics. We present new cytogenetic data for nine species of pike cichlid, the chromosomal mapping of 5S rDNA for Crenicichla and other three species ( Lugubria cincta , L . lugubris and Saxatilia semicincta ), including available review of cytogenetic studies in Crenicichlina. Cytogenetic data for Crenicichla show a conserved cytotaxonomic pattern for most of the analyzed species: single 5S and 18S rDNA sites always in interstitial position centromeric heterochromatin. Lugubria showed greater variation in chromosomal characters, mainly an increase in 18S rDNA sites, always in terminal position and associated with heterochromatin. On the other hand, Saxatilia showed the same 18S rDNA pattern as Crenicichla , but with the presence of multiple 5S rDNA sites. Finally, karyotype of one species of Wallaciia that was analyzed possessed single 5S rDNA sites and multiple NORs. Although some chromosomal characters are conserved in Cichlinae, interspecific differences were verified in the karyotypic composition, as possible intragenus patterns. Chromosomal characters, mainly 5S and 18S rDNA, proved to diagnose species as well as they contribute to phylogenetic studies in pike cichlids. Graphical Abstract