Frequencies of codons ended with the same nucleotide on total and each strand (H, L) of O. lacepedi, O. rebecca and O. 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. lacepedi. ORE, O. rebecca. OSP, O. sp.