Cytogenetic analyses in three species of Moenkhausia Eigenmann, 1903 (Characiformes, Characidae) from Upper Paraná River (Misiones, Argentina)

SÁNCHEZ, KEVIN IMANOL; TAKAGUI , FABIO H.; FENOCCHIO, ALBERTO S.

CARYOLOGIA

UNIV FLORENCE BOTANY INST

Lugar: Florencia; Año: 2022 vol. 74 p. 3 - 10

0008-7114

Moenkhausia Eigenmann, 1903 is one of the most diverse genera within Characidae, being an important component of the Neotropical fish fauna. Three members of this genus were cytogenetically analyzed: M. dichroura Kner, 1858, M. intermedia Eigenmann, 1908 and M. sanctaefilomenae Steindachner, 1907. The three species showed 2n = 50 bi-armed chromosomes (NF = 100) and different karyotype formulas: 22m + 22sm + 6st in M. dichroura, 16m + 28sm + 6st in M. intermedia, and 12m + 32sm + 6st in M. sanctaefilomenae. In addition, supernumerary chromosomes (or B-chromosomes) were detected in M. intermedia and M. sanctaefilomenae. C-positive bands were restricted to pericentromeric regions, secondary constrictions and supernumerary chromosomes. Active nucleolus organizer regions (Ag-NORs) and positive CMA3 bands were observed in a single pair of sm chromosomes. Pericentromeric DAPI positive signals were evidenced on chromosomes of M. sanctaefilomenae only. Overall, the three species showed a conservative karyotype macrostructure (diploid number, number of chromosome arms) and variations in microstructure (karyotype formulas, presence/absence of supernumerary chromosomes). We discuss how the observed differences could have been shaped.