Ocorrência simpátrica de três cariomorfos de Hoplias malabaricus para a região do Baixo Iguaçu, Realeza, Paraná

Abstract

The Iguaçu River Basin is divided into Upper, Middle and Lower Iguaçu, born in the Serra Geral and with Foz in the Iguazu Falls, an important geographical barrier that separates the Iguaçu River basin from the Paraná River basin. The ichthyofauna of this basin is very diverse, with a high degree of endemism, with about 70% of endemic fish species. Among the eight orders of fish found, the most representative in number of species are Siluriformes, Characiformes and Perciformes. Among the Characiformes, the family Erythrinidae has three genera, one of them the genus Hoplias, composed of two species groups, Hoplias malabaricus and Hoplias lacerdae. Hoplias malabaricus is a species of fish, popularly known as traíra, considered morphologically as a single biological species, but with interpopulational chromosomal differences that show the existence of at least seven species within this group, called karyomorphs. The aim of this work is to analyze populations of Hoplias malabaricus present in the Capanema River, in Realeza, Paraná, in the final portion of the lower Iguaçu River. For this work, the specimens were collected and kept in aerated aquariums. Mitoses were stimulated by yeast, colchicine was applied to inhibit mitotic spindles, followed by clove oil overdose and kidney extraction to obtain the metaphase chromosomes. Slide preparation was performed by sequential analysis with Giemsa, followed by C-banding to identify constitutive heterochromatin regions. The chromosomes were classified into Metacentric, Subcentric, Subtelocentric or Telocentric and arranged in homologous pairs. The results show that there is the presence of three H. malabaricus karyomorphs in the study region, which are Karyomorph A, with 2n = 42 chromosomes, without apparent sex chromosomes and 26M + 16SM karyotype formula, for males and females; Karyomorph B, with diploid number of 42 chromosomes and a simple sex chromosome system, XX / XY and karyotypic formula 24m + 16sm + 2st for females and 23m + 18sm + 1st for males; and karyomorph D, with diploid number 39 chromossomes in male (23m + 16sm) and 40 chromossome from female (20m + 20sm) and complex sex chromosome system X1X1X2X2 / X1X2Y. Karyomorph A is considered natural for the Iguaçu basin, while karyomorph B is described for a lacustrine system in the Rio Doce valley and for the Upper Iguaçu River and Upper Paraná. Karyomorph D is endemic to the Upper Paraná River region, which is the first description of the presence of karyomorph D in another basin, thus representing a new region of occurrence of karyomorph D. Our hypothesis is that the presence of these karyomorphs in this region occurs by anthropic influence through the purchase and sale of fingerlings from the Upper Paraná River region which may have been brought to the fishing stations of this region and migrated to the rivers during times of flooding. Thus, the implantation of exotic karyomorphs can alter local biodiversity, as studies have shown that some karyomorphs are more aggressive than others, and there is a dispute for food and territory between different karyomorphs.