Cytogenetic study of two species of needlefish (Belonidae) from Argentina

The chromosomes of the: two species of needlefish, Potamorraphis cf. eigenm anni and Strongylura microps, from fresh waters of Argentina were analyzed using C-banding and silver staining and their karyotypes a ere described fo r the first time. The former species possessed 2n = 54 and karyotype compos ed of three pairs metacentric to submetacentric chromosomes and 24 pairs of subtelo to telocentric chromosomes. The NORs were situated on the the end of the shorter arms of one middle-sized bi-armed pair of chromosomes. The l ater species possessed 2n = 50 and karyotype composed exclusively of subtel o to telocentric chromosomes gradually decreasing in size, The NORs were si tuated interstitially on the third pair of chromosomes. One or two supernum erary chromosomes a ere observed in one individual of the sample. Present d ata indicate greater cytotaxonomic diversity among species of needlefish wh ich might be associated with their colonization of fresh waters.