Frequencies of codons ended with the same nucleotide on total and each strand (H, L) of O. lacepedii, O. rebecca and Odontamblyopus sp. mitogenomes. Values on the Y-axis indicate the sum of RSCU values of codons ended with the same nucleotide across all codon families (X-axis). RSCU, relative synonymous codon usage; OLA, O. lacepedii; ORE, O. rebecca; OSP, Odontamblyopus sp.