Nucleotide skews, codon usage, amino acid usage, and G + T content of the three studied mitogenomes, and comparison with other flatworms. a-d Comparison of nucleotide skews of the full genomes, protein-coding genes (PCGs), tRNAs and rRNAs for the mitogenomes of Paradiplozoon opsariichthydis, Sindiplozoon sp. and Eudiplozoon sp., and other flatworms. e, f Principal component (PC) analysis of the codon usage and amino acid usage in the PCGs of the three studied diplozoids and other flatworms. The first PC (PC1) and the second PC (PC2) of the codon usage and amino acid usage accounted for 95.8% and 94.7% of the variability, respectively. g G + T content and skewness of complete genomes and their individual elements. Species are colored according to their taxonomic placement at the class level in figure panels a-f and family level in the panel g. The three studied diplozoids are represented by triangles. ES: Eudiplozoon sp.; PO: Paradiplozoon opsariichthydis; SS: Sindiplozoon sp.