Chromosomal Analysis of Ctenolucius hujeta Valenciennes, 1850 (Characiformes): A New Piece in the Chromosomal Evolution of the Ctenoluciidae

Ctenoluciidae (Characiformes), a family of freshwater fishes, comprises 2 genera, Ctenolucius and Boulengerella, with 7 recognized species. Up to now, only species of the genus Boulengerella have been subjected to cytogenetic studies. Here, we investigated the karyotype and other cytogenetic features of pike characin, Ctenolucius hujeta, using conventional (Giemsa staining, C-banding, Ag-NOR staining) and molecular (rDNA, telomeric sequences, and fiber-FISH mapping) procedures. This species has a diploid chromosome number of 2n = 36, and a karyotype composed of 12m + 20sm + 4a and FN = 68, similar to that found in Boulengerella species. However, differences regarding the number and distribution of several chromosomal markers support a distinct generic status. Colocalization of the 18S and 5S rDNA genes is an exclusive characteristic of the C. hujeta genome, with an interspersed distribution in the chromosomal fiber, an unusual phenomenon among eukaryotes. Additionally, our results support the view that Ctenoluciidae and Lebiasinidae families are closely related.

Automated summary

The study investigated the karyotype and cytogenetic features of pike characin, Ctenolucius hujeta, revealing similarities with Boulengerella species but also unique chromosomal marker distributions. The colocalization of the 18S and 5S rDNA genes is identified as a distinctive characteristic of the C. hujeta genome. Additionally, the research supports a close relationship between the families Ctenoluciidae and Lebiasinidae.