Chromosome characterization in Acestrorhynchinae and Cynopotaminae (Pisces, Characidae)

The karyotypes of six species of Acestrorhynchinae ( Acestrorhynchus alus, A. lacustris, Oligosarcus hepsetus, O. jenynsii, O. macrolepis and O. pinloi ) and of one species of Cynopotaminae ( Galeocharax knerii ) were studied. The six Acestrorhynchinae species have 2 n = 50, while Galeocharax knerii has 2 n = 52 chromosomes. Some chromosomal characteristics were detected which permit establishing some karyotypic relationships among the different species investigated. Thus, among the Acestrorhynchinae, the four Oligosarcus species are relatively more related to one another than the two Acestrorhynchus species, at least with respect to the cytogenetic data considered. On the basis of the methods used, no sex chromosome heteromorphism was detected in the species for which a comparative study between male and female specimens was possible.     

Karyotype evolution in Curimatidae (Teleostei, Characiformes) from the Amazon region. II. Centric fissions in the genus Potamorhina

Using cytogenetic analysis following Giemsa staining, nucleolar organizer region (NOR) staining, and C-banding, three distinct karyotypes in three species of curimatids belonging to the fish genus Potamorhina were identified: 2n = 54/44 M + 10 SM (P. pristigaster), 2n = 56/52 M + 2 SM + 2 ST (P. latior), and 2n = 102/2 M + 2 SM + 98 A (P. altamazonica). A 2n = 54 was considered to be the ancestral diploid number and the different karyotypes were probably the result of centric fissions. Both the NOR pattern and constitutive heterochromatin pattern are species specific.