Genetic diversity and structuring in the arapaima (Osteoglossiformes, Osteoglossidae) population reveal differences between the Amazon and the Tocantins-Araguaia basins.

Fabrícia Nogueira,Péricles S Do Rêgo,Paulo Venere,Horacio Schneider,Iracilda Sampaio,Eduardo S Varela,Juliana Araripe,Helder Queiroz

doi:10.1590/0001-3765202020180496

Abstract

Arapaima is a widely-distributed fish of enormous economic importance in the Amazon region. In the present study, a total of 232 specimens were sampled, 121 from five sites in the Amazon basin and 111 from five sites in the Tocantins-Araguaia basin. The analyses investigated fragments of the Cytochrome b, Control Region, Cytochrome Oxidase I, NADH dehydrogenase subunit 2 and seven loci microsatellites. The analyses revealed the existence of two mitochondrial lineages within the general area, with no haplotypes shared between basins, and genetic variability significantly higher in the Amazon than in the Tocantins-Araguaia basin. Two divergent, but sympatric mitochondrial lineages were found in the Amazon basin, but only a single lineage in the Tocantins-Araguaia basin. The existence of these two mitochondrial lineages indicates that past events, probably occurring during the Pleistocene, resulted in the separation of the populations of this species and molded its evolutionary history, which is reflected directly in its mitochondrial DNA. The analysis of the arapaima population structure identified distinct levels of diversity within the distribution of the species, indicating specific geographic regions that will require special attention for the development of conservation and management strategies.

Highlights

The arapaima, Arapaima gigas Schinz, 1822, is one of the largest freshwater fish in the world, reaching up to 3 m in total length and weighing over 200 kg (Nelson et al 2016)
A total of 1,241 base pairs (567 bps for Cytochrome b (Cytb) and 674 bps for the Control Region) of the mitochondrial genome were obtained from the 121 arapaima specimens collected from the Amazon basin and the 111 specimens from the Tocantins-Araguaia basin
Sites in the Tocantins-Araguaia basin exhibited moderate to low levels of genetic variability, with haplotype diversity ranging from zero to 0.597 and nucleotide diversity from zero (Lagoa da Confusão and Quatro Bocas) to 0.00067 (Caseara) (Table I)

Summary

Introduction

The arapaima, Arapaima gigas Schinz, 1822, is one of the largest freshwater fish in the world, reaching up to 3 m in total length and weighing over 200 kg (Nelson et al 2016) This species prefers lentic habitats, such as floodplains and lakes (Castello 2008). This important fishery resource has a long history of exploitation, as shown by records of fishery landings at the main ports of the Amazon region. For this reason, the arapaima was included in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), a list of threatened species that may become extinct unless trade is strictly controlled (CITES 2017). Population and phylogeographic studies of the arapaima have identified different levels of structuring in the populations within the Amazon and Tocantins-Araguaia basins, the samples analyzed in these studies were not adequate for conclusive comparisons of the

Methods

Results

Conclusion