Loricariidae (Siluriformes, Hypostominae) is one of the most diverse catfish families. In spite of the wide distribution of loricariids in South America, cytogenetic reports are available for only a few species, mostly from southern and southeastern Brazil. We made the first chromosomal analysis of Hypostomus aff. unae from the Contas River basin in northeastern Brazil.
Triple staining with fluorochromes (DA/DAPI/CMA) and C-banding were used to characterize the composition of Pseudonannolene strinatii heterochromatin. C-banding showed C+ bands of different labeling intensity on chromosomes 1 and 2 in some cells. Fluorochrome staining revealed DAPI+ regions corresponding to the C-banding pattern, indicating that the heterochromatin of this species is abundant in AT-rich sequences.