Characterization and comparative analysis of the complete mitochondrial genome of Azygia hwangtsiyui Tsin, 1933 (Digenea), the first for a member of the family Azygiidae

Abstract

<i>Azygia hwangtsiyui</i> (Trematoda, Azygiidae), a neglected parasite of predatory fishes, is little-known in terms of its molecular epidemiology, population ecology and phylogenetic study. In the present study, the complete mitochondrial genome of <i>A. hwangtsiyui</i> was sequenced and characterized: it is a 13,973 bp circular DNA molecule and encodes 36 genes (12 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes) as well as two non-coding regions. The A+T content of the <i>A. hwangtsiyui</i> mitogenome is 59.6% and displays a remarkable bias in nucleotide composition with a negative AT skew (-0.437) and a positive GC skew (0.408). Phylogenetic analysis based on concatenated amino acid sequences of twelve protein-coding genes reveals that <i>A. hwangtsiyui</i> is placed in a separate clade, suggesting that it has no close relationship with any other trematode family. This is the first characterization of the <i>A. hwangtsiyui</i> mitogenome, and the first reported mitogenome of the family Azygiidae. These novel datasets of the <i>A. hwangtsiyui</i> mt genome represent a meaningful resource for the development of mitochondrial markers for the identification, diagnostics, taxonomy, homology and phylogenetic relationships of trematodes.