The distribution of mtDNA cyt b haplotypes plotted on the maximum parsimony (MP) haplotype–haplogroup network of A. anguilla mtDNA D-loop region (Ragauskas et al., 2014): numbers between the nodes are mutational steps between the most closely related sequences; the radius of the circles is proportional to the frequency of mtDNA D-loop region haplotypes; mv represent hypothetical sequences that were not found during the study but are important to the construction of the haplotype network; gray shapes represent different haplogroups of mtDNA D-loop region; different colors represent different mtDNA cyt b haplotypes; white circles represent mtDNA D-loop region haplotypes detected in the eels that were not examined using mtDNA cyt b.