Estimativa da diversidade genética da piraíba (Brachyplatystoma filamentosum Lichtenstein, 1819) e da piraíba negra (Brachyplatystoma capapretum Lundberg e Akama, 2005), na Amazônia Brasileira, inferidas por meio do DNA mitocondrial: subsídios para manejo e conservação

Abstract

The piraíba (B. filamentosum, Siluriformes: Pimelodidae) has a wide distribution in the Amazon basin, occurring from coastal rivers of Amapá state to the water courses across foothills of the Andes. Since the 1970s there were doubts about the existence of one or more species called piraíba, but in 2005 a new species named black piraíba (Brachyplatystoma capapretum) was described based on mofological characters. There are few data on the biology of piraíba and these are usually treated together with other species of large catfish. This thesis is written and divided into two chapters. In the first chapter, the two species known as piraíba (Brachyplatystoma filamentosum and Brachyplatystoma capapretum) from fishery landings held in 9 regions inserted in white water rivers basins of the Brazilian Amazon, were genetically characterized through mitochondrial DNA control region. For a total of 337 samples, it was verified that, in medium, in all sampled area, 66.81% of the fishes belonged to B. filamentosum species and 33.19% to B. capapretum species. The values of haplotypic diversity were high for both species, however the nucleotide diversity was higher in B. filamentosum (π= 0.0118) when compared to B. capapretum (π= 0.0041). These values were compared to the nucleotide diversity values of other overfished species or threatened species in the Amazon and suggesting that the B. filamentosum and B. capapretum need urgent management actions for conservation. The nucleotide substitution model Tamaura-Nei showed that the genetic divergence between this species was 0.1018. This value can be used as a reference for genetic distance studies for others Brachyplatystoma species. The second chapter aimed to infer the genetic structure of B. filamentosum in the Brazilian Amazon, through the sequencing of the control region of mitochondrial DNA. 262 samples of B. filamentosum were analyzed from the commercial catch in nine regions characterized by having white-water rivers, two regions of rivers with clear waters and one region with a black waters river. The SAMOVA resulted in Fct =0.62079, for k = 3 groups, where the regions sampled were grouped according to water type. Phylogenetic analysis indicated the existence of three clades that have a strong relationship with the geographical distribution of three types of waters of the Amazon basin. Clades related to the clear and black waters showed low diversity of nucleotydes (π = 0,0037 and 0.0036 respectively). The results were discussed in the evolutionary context of the Amazon basin and also revealed the need for management actions for conservation purposes for B. filamentosum.