Detailed characterization of the complete mitochondrial genome of the oceanic whitetip shark Carcharhinus longimanus (Poey, 1861).

ABSTRACT

BACKGROUND: The oceanic whitetip shark Carcharhinus longimanus (family Carcharhinidae) is one of the largest sharks inhabiting all tropical and subtropical oceanic regions. Due to their life history traits and mortality attributed to pelagic longline fishing practices, this species is experiencing substantial population decline. Currently, C. longimanus is considered by the IUCN Red List of Threatened Species as "vulnerable" throughout its range and "critically endangered" in the western north Atlantic. This study sequences and describes the complete mitochondrial genome of C. longimanus in detail. METHODS AND RESULTS: The mitochondrial genome of C. longimanus was assembled through next-generation sequencing and then analyzed using specialized bioinformatics tools. The circular, double-stranded AT-rich mitogenome of C. longimanus is 16,704 bp long and contains 22 tRNA genes, 2 rRNA genes, 13 protein coding genes and a 1,065 bp long control region (CR). Out of the 22 tRNA genes, only one (tRNA-Ser1) lacked a typical 'cloverleaf' secondary structure. The prevalence of TTA (Leu), ATT (Ile) and CTA (Leu) codons in the PCGs likely contributes to the AT-rich nature of this mitogenome. In the CR, ten microsatellites were detected but no tandem repeats were found. Stem-and-loop secondary structures were common along the entire length of the CR. Ka/Ks values estimated for all PCGs were < 1, indicating that all the PCGs experience purifying selection. A phylomitogenomic analysis based on translated PCGs confirms the sister relationship between C. longimanus and C. obscurus. The analysis did not support the monophyly of the genus Carcharhinus. CONCLUSIONS: The assembled mitochondrial genome of this pelagic shark can provide insight into the phylogenetic relationships in the genus Carcharhinus and aid conservation and management efforts in the Central Pacific Ocean.