Cytogenetic studies in <i>Hasemania crenuchoides</i> (Characiformes: Characidae) and molecular investigations into kinship relationships of the genus

The genus <i>Hasemania</i> is considered <i>incertae sedis</i> from the family Characidae which possesses nine fish species. <i>Hasemania crenuchoides</i> is endemic to the Federal District of Brazil and is under threat of extinction. The objective of this work was to characterize the <i>Hasemania crenuchoides</i> karyotype and investigate phylogenetic relationships using the 5ʹ region of the COI gene. Our results showed a chromosome number of 2<i>n</i> = 50, with a fundamental number equal to 82 and a karyotype formula of 32m/sm+ 18st/a. C banding evidenced that constitutive heterochromatin is not only present in pericentromeric regions, but also in telomeric and interstitial regions. Ag-NOR marking occurred in the short arm of pair 6. DAPI staining revealed that few bands were rich in A/T. The diploid number observed is in accordance with previous findings in Characidae, including the presence of a long metacentric pair, and is considered a plesiomorphic character. Based on the literature, together with cytogenetic and molecular data, it is suggested that <i>Hasemania</i> is possibly not monophyletic, composed of two groups: (1) a basal group with <i>H. hanseni</i> and <i>H. nana</i>; and (2) a derived group with <i>H. crenuchoides</i>, <i>H. kalunga</i>, and <i>H. uberaba</i>. Therefore, the molecular and cytogenetic data presented may contribute to understanding phylogenetic relationships within the family.