Mitochondrial genome organization of Calanoida copepod Calanus sinicus. direction of gene transcription is indicated by the arrows. Protein-coding genes are shown as blue arrows, rRNA genes as purple arrows, tRNA genes as red arrows and large non-coding regions (>100 bp) as cyan rectangles. tRNA genes are labelled by single-letter IUPAC-IUB abbreviations (L1: CUN; L2:UUR; S1:AGN; S2:UCN) while other genes are represented as outlined in the abbreviations section. Ticks in the inner cycle indicate the sequence length.