Comparative analysis of mitochondrial genomes between FCDK and
FCSH
The mitochondrial genomes of both FCDK and FCSH share the ancestral gene
order found in Pancrustracea. The genome sizes of the two strains were
slightly different, at 15,141 bp for FCSH and 15,177 bp for FCDK, with a
36 bp insertion in the FCDK mitochondrial sequence between trnQ and trnM
(Figure 5a, b). Fourteen out of 37 mitochondrial genes shared the same
gene length in FCDK and FCSH. The overall sequence identity between the
two mito-genomes was 78.2% (Figure 5c). The average pairwise
identity was 77.13% for 13 CDSs,
87.0% for 22 tRNAs, 82.6% for 2 rRNAs, and 60.2% for the noncoding
regions. The pairwise identity of the standard barcoding region (a 658
bp sequence in the 5’ region of the cox1 gene) in these two
sibling species was 80.9%. Such great sequence divergence would be
unlikely to be attributable to intraspecies variation. Strengthened by
the mitochondrial genome analyses, FCDK and FCSH should be regarded as
two distinct species.