Variabilidade genética de tucunarés (Cichlidae: cichliformes) introduzidos em bacias hidrográficas maranhenses

Abstract

The genus Cichla, the tucunarés, originating from the Amazon basin, are fish of great economic and ecological importance, whether for sport fishing, fish stocking or cooking. They are voracious predators, present in 16 species that have been introduced in several river basins in Brazil, among them the Maranhão basins and little is known about these species, in relation to taxonomic identification, number of individuals and their genetic variability. Therefore, we used the mitochondrial genes 16S ribosomal RNA (16S rRNA) and Cytochrome b (Cyt b) to analyze the levels of genetic variability of the genus Cichla introduced in the basins of Maranhão. The specimens were collected in the Mearim and Parnaíba/MA basins using fishing gear, and then transported to the Molecular Biology Laboratory (LABMOL) where they were sorted, labeled, photographed and identified using specific literature and subjected to DNA extraction techniques, amplification of 16S rRNA and Cyt b genes via PCR and sequencing. The obtained sequences were analyzed in the software: BioEdit, Mega X, DnaSP. 23 sequences were obtained for both genes, of which, 13 from the Flores river, five from the Pindaré river, Mearim river basin and five from the Buriti river, a tributary of the Parnaíba river basin. Sequences of the genus Cichla from Genbank were added to this work for analysis purposes, 22 for the rRNA16S gene and 23 for Cyt b. The 16S rRNA fragment showed values of haplotype diversity (h) of 0.676and nucleotide (π) of 0.019, 12 haplotypes were formed, among which, there was the formation of a single haplotype for specimens of Cichla kelberi from Maranhão rivers and Genbank sequences with an intraspecific genetic distance of 0.0%. The Cyt b gene showed an intraspecific divergence that ranged from 0.0 to 0.5%, with a haplotype diversity (h) of 0.838 and nucleotide diversity(π) of 0.041, and a total of 21 haplotypes, two haplotypes for specimens of C. kelberi from Maranhão basins and one for Genbank sequences. The clusters generated by phylogenetic reconstructions for both genes showed strongly supported clades, indicating agreement with the species Cichla kelberi. The specimens analyzed by 16S rRNA were grouped into a clade coherently with the specimens collected in the Doce and Itumbiara rivers/MG, which come from the Tocantins river. Given this, it is possible to infer that the specimens of Cichla kelberi collected in the Flores, Pindaré and Buriti/MA rivers are derived from populations of the Tocantins river. Therefore,fragments of the 16S rRNA and Cyt b genes proved to be a useful tool for taxonomic identification at a specific level, recurrent introduction events are of great ecological concern, causing impacts on the native ichthyofauna, these results can help in tracking the origin of the Cichla in the basins of Maranhão, helping in the analysis of the genetic variability of introduced stocks