Diversidade e evolução cromossômica em Loricariidae (Rafinesque, 1815)

Abstract

Loricariidae is one of the largest families of freshwater fish, distributed throughout the Neotropical region, exhibiting wide diversity in morphological and cytogenetic traits. Research focusing on the cytogenetic description of species populations within this group enhances the understanding of their evolutionary aspects. This study aims to analyze cytogenetic data of the Loricariidae family, summarizing its chromosomal diversity and evolution, and providing a cytogenetic description of species from the Paraná Basin, Brazil. The results of this research were organized into two articles. The first article analyzes three loricariid species: Pterygoplichthys ambrosettii, Loricariichthys platymetopon, and Hypostomus ancistroides. The diploid number of 52 chromosomes was observed in P. ambrosettii (40m/sm+12st/a), 54 chromosomes in L. platymetopon (24m/sm+30st/a), and 68 chromosomes in H. ancistroides (24m/sm+30st/a). P. ambrosettii and L. platymetopon exhibited simple AgNORs, interstitially located on the long arm of chromosome pair 14 and on the telomeric region of the short arm of pair 13. H. ancistroides showed multiple AgNORs, observed on the telomeric region of the short arm of one chromosome from pair 13 and both chromosomes of pair 24. In addition to these results, the first article summarizes the cytogenetic data available in the literature for the Loricariidae subfamilies, discussing existing results and their evolutionary implications with support from phylogenetic proposals. It was observed that groups like the Hypostominae and Loricariinae subfamilies present considerable karyotypic diversity, whereas others, like the Rhinelepinae subfamily, retain more conserved characteristics. The second article describes the cytogenetic profiles of Hypostomus commersonii populations from the Piquiri and Iguaçu Rivers and discusses karyotypic diversity within Hypostominae, focusing on species that exhibit inter- and intrapopulational variation according to literature data. A diploid number of 68 chromosomes was identified for individuals from both populations of H. commersonii, distributed as +14sm+14st+28a. Constitutive heterochromatin was mainly observed in the centromeric region of the chromosomes, with one individual showing polymorphism related to GC-rich heterochromatin. Multiple AgNORs were identified in both populations, confirmed by 18S rDNA probes. Furthermore, the cytogenetic data documented for Hypostominae and summarized in this work highlighted the extent of interpopulational variation within species, particularly regarding diploid number, karyotypic formula, and nucleolar organizer regions.