Karyotypic studies on two Hoplias malabaricus populations (Characiformes, Erythrinidae) of the 2n=42 group, from the first plateau of the Iguacu river basin (Parana State, Brazil)

摘要

Hoplias malabaricus represent a clear example of a species complex, including several karyotypic forms with chromosome numbers ranging from 2n = 39/40 to 2n = 42, including case's of simple and multiple sex chromosome systems. In this work were cytogenetically analyzed two populations of this "species". The samples were obtained at the first plateau of the Iguacu river (Parana State, Brazil). The results show that both populations have the same chromosome number (2n = 42) but one of them appears to be characterized by a sex chromosome system with male heterogamety (XX/XY). A such system was also previously described in H. malabaricus from another Brazilian region. Thus, the presence of this differentiated sex chromosome system in this river basin suggests that it was originated before the geographic isolation of the studied populations. The present data represent an additional support for the proposition that Hoplias malabaricus constitutes a species complex. [References: 17]