The complete mtDNA D-Loop sequences with 1008 bp in length were obtained from 180 wild individual samples.
The average nucleotide compositionwas 32.1% A, 31.0% T, 23.7% C and 13.2% G, contents A þT (55.8%)was higher than that of C þ G (44.3%), which showed A and T were richer in the swamp eel mtDNA D-Loop region.
212 polymorphic sites were found in the six populations. The HB population had the most polymorphic sites (N ¼ 173) and the CQ population had the least (N ¼ 4) in all the populations (Table 2).
123 of the 212 polymorphic sites were singleton variable sites and the other 89 were parsimony
informative sites.