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
ishing
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 conirms 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
eforts
in
the
Central
Paciic
Ocean
