The complete mitochondrial genome of Giant African threadfin, Polydactylus quadrifilis (Curvier, 1829) (Perciformes: Polynemidae) from Liberia

Abstract

Fish species identification is crucial and equally important for fisheries resource management and its sustainability, which provide the basic criteria for biodiversity monitoring and conservation of the species stock biomass. Using a molecular technique such as sequencing the complete mitochondrial DNA to provide an accurate and fast result for species identification as an alternative method to morphological identification method is emerging. In this research, the complete mitochondrial DNA sequence of Giant African threadfin, Polydactylus quadrifilis (Curvier, 1829) was acquired through the MiSeq platform. The accumulated size of P. quadrifilis complete mitochondrial genome was 16,849 bp in length (GenBank accession number: MH995529), it contained 37 genes, including 13 protein-coding genes, 22 tRNAs, 2 rRNAs, and 2 non-coding regions (an origin of light strand replication, OL and D-loop control region, CR). The overall G+C content (45.80%) was less than the A+T content (54.20%), indicating high purine and pyrimidine. Eleven protein-coding genes commenced with a typical start codon (ATG). Unusual start codons include GTG (COX1), and ATC (ATP6). Six protein-coding genes terminated with typical TAA, two genes (ND5 and ND6) terminated with TAG stop codons. An unusual stop codon (AGA) was identified in COX1 and incomplete stop codon (TA-/T--) was identified in 4 genes including ND2, COX2, ND3, and ND4. Transfer RNAs genes were interspersed on each strand of the mitogenome structure, 8 tRNA genes on the L-strand whereas, 14 tRNA genes were on H-strand. The phylogenetic tree analysis showed six species in Polynemidae family including P. quadrifilis were grouped together. Among them, P. quadrifilis was most closely related to Polydactylus sextarius (GenBank No. NC027088) with 80% nucleotide sequence identity. To discriminate between the two species of Polydactylus genus, both morphological and molecular characteristics can be used for distinction by taking into account the thread-like filaments on the pectoral fin of both species, and comparing the size of the complete mitochondrial DNA sequences for the reliable taxonomical classification.