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Abstract
DNA barcoding has been adopted as a gold standard rapid, precise and unifying identification system for animal species and provides a database of genetic sequences that can be used as a tool for universal species identification. In this study, we employed mitochondrial genes 16S rRNA (16S) and cytochrome oxidase subunit I (COI) for the identification of some Nigerian freshwater catfish and Tilapia species. Approximately 655 bp were amplified from the 5' region of the mitochondrial cytochrome C oxidase subunit I (COI) gene whereas 570 bp were amplified for the 16S rRNA gene. Nucleotide divergences among sequences were estimated based on Kimura 2-parameter distances and the genetic relationships were assessed by constructing phylogenetic trees using the neighbour-joining (NJ) and maximum likelihood (ML) methods. Analyses of consensus barcode sequences for each species, and alignment of individual sequences from within a given species revealed highly consistent barcodes (99% similarity on average), which could be compared with deposited sequences in public databases. The nucleotide distance between species belonging to different genera based on COI ranged from 0.17% between Sarotherodonmelanotheron and Coptodon zillii to 0.49% between Clarias gariepinus and C. zillii, indicating that S. melanotheron and C. zillii are closely related. Based on the data obtained, the utility of COI gene was confirmed in accurate identification of three fish species from Southwest Nigeria.
Highlights
The use of a globally recognized short DNA sequence, DNA barcode, for identification of species has gained global support as an applicable tool for species identification, with respect to fishes as coordinated by the fish barcode of life (FISH-BOL; www.fishbol.org)[1]
The mitochondrial genes cytochrome oxidase I (COI) and 16S have been successfully employed in species identification based on DNA barcodes[10] and a series of barcoding projects involving various organisms from different geographic regions is available at the public barcode library[11]
Nucleotide composition of the 16S rRNA analysis gave a total of 1049 nucleotide sites and revealed the mean frequencies for the dataset to be 269 bp/site (25.64%) conserved, 338 (32.22%) variable, 183 (17.45%) parsimony informative and 155 (14.78%) singletons
Summary
The use of a globally recognized short DNA sequence, DNA barcode, for identification of species has gained global support as an applicable tool for species identification, with respect to fishes as coordinated by the fish barcode of life (FISH-BOL; www.fishbol.org)[1]. Fish biodiversity in tropical Africa demonstrate an amazing variety of shape, size, and color. Many of these fishes are under immense pressure from overfishing and climate change. DNA barcoding has been used to identify species and is important in characterizing biological diversity. This technique involves the amplification and sequencing of short universal molecular tags from a highly conserved gene. The mitochondrial genes COI and 16S have been successfully employed in species identification based on DNA barcodes[10] and a series of barcoding projects involving various organisms from different geographic regions is available at the public barcode library (www.barcodinglife.com)[11]
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