Cytogenetics and biogeography:: Considerations about the natural origin of Hoplias malabaricus (Characiformes, Erythrinidae) on the Iguacu river

Hoplias malabaricus (trahyra) is a widespread fish species over the Neotropical region with diversified interpopulational karyotypes (cytotypes), which may correspond to a species complex. Despite the wide distribution in the South American basins, some authors have questioned its natural origin in the lguacu river, an important Brazilian river basin which is characterized by several endemic fish species. We have analyzed the karyotype of H. malabaricus from different collection sites of this river, by conventional and banding methods. Our results, in addition to our previous data concerning geographic distribution of the cytotypes, contribute to better understand the origin of H. malabaricus on the Iguacu river, reinforcing the proposition that it is a natural fish species in this river basin.