Análises cromossômica e molecular de Pterygoplichthys Pardalis (Castelneau, 1855) (Siluriformes: loricariidae): uma espécie nativa da Bacia Amazônica e invasora em outros países

Abstract

Pterygoplichthys pardalis is one of the 15 species that make up the genus Pterygoplichthys Family Loricariidae, Order Siluriformes. This group of fish is native to South America, but there is a record of introduction in five continents and exotic populations of P. pardalis have settled in 16 countries. Despite its commercial and socioenvironmental importance, P. pardalis is still poorly studied from a genetic perspective. In this work, we describe for the first time the karyotype of P. pardalis and compare individuals from native and exotic populations through the mitochondrial gene Cytochrome oxidase I. Ten individuals collected in Lake Pacoval and Lake Arapixuna, on the right bank of the Amazon River, were analyzed. The karyotype showed diploid number 2n=52 and NF=100 with no morphological variation between males and females. The location of the nucleolus organizer regions and the 18S ribosomal marker were coincident in pair 14, while the 5S site was detected in the interstitial position of pair 13. The constitutive heterochromatin is restricted and located in the telomeric region of only four pairs, of which three recorded positive CMA3 signals at the same location. Telomeric markings were observed only at the ends of chromosomes. The species P. pardalis diverged from other congeners due to variation in the karyotype formula. The molecular variation of the Cytochrome oxidase I gene revealed five mutations that differentiate four haplotypes. Haplotype 1 is the most frequent and shared by individuals from native and exotic populations. The exotic population of the Philippines is the most diverse and may represent the original introduction event of P. pardalis into Southeast Asia.