First description of the karyotype and Ag-NORs localization of Brachychalcinus retrospina (pisces: Characidae: Stethaprioninae) from upper Paraguay Basin, Mato Grosso state, Brazil

摘要

Cytogenetic studies in fish can be used to discuss the evolution and phylogeny of the species, since the chromosomes are the physical basis of the genetic system of an organism. Thus, our objective was to study chromosomally the fish species Brachychalcinus retrospina to enlarge the number of karyotyped species for the Brachychalcinus genus. Specimens of B. retrospina from Angelim River, Nova Olímpia, Mato Grosso State, Brazil, presented 2n = 50 chromosomes: 16 metacentric, 24 submetacentric, six subtelocentric and four acrocentrics. The Nucleolus Organizer Regions (NOR) was detected in one chromosome pair. The results for B. retrospina corroborate those found for other species this subfamily, both in chromosome number and markings of Ag-NORs, indicating some stability chromosomal for this group.