Table 1. Summary of codon usage in the seven nemertean mitochondrial genomes.

Species	Classification	Genome size (bp)	Protein coding gene	GC all (%)	GC1(%)	GC2(%)	GC3(%)	AT skew	GC skew	ENc
Cephalothrix hongkongiensis	Paleonemertea	16,296	13	26.6	34.6	33.8	11.4	−0.27	0.19	33.7
Cephalothrix sp.	Paleonemertea	15,800	13	25.5	34.2	33.5	8.7	−0.27	0.18	32.5
Lineus alborostratus	Heteronemertea	15,476	13	37.2	43.6	37.7	30.1	−0.35	0.31	51.0
Lineus viridis	Heteronemertea	15,388	13	35.9	43.1	37.8	26.8	−0.27	0.29	39.5
Zygeupolia rubens	Heteronemertea	15,513	13	35.8	44.0	36.8	26.6	−0.36	0.42	35.9
Emplectonema gracile	Hoplonemertea	14,666	13	32.0	39.5	34.9	21.7	−0.44	0.22	39.6
Nectonemertes cf. mirabilis	Hoplonemertea	15,365	13	31.3	36.7	33.6	23.6	−0.38	0.29	36.8
Paranemertes cf. peregrina	Hoplonemertea	14,558	13	30.1	37.4	34.4	18.4	−0.35	0.32	35.6