Tandemly repeated sequence in 5'end of mtDNA control region of Japanese Spanish mackerel Scomberomorus niphonius

Extensive length variability was observed in 5’ end sequence of the mitochondrial DNA control region of the Japanese Spanish mackerel (Scomberomorus niphonius). This length variability was due to the presence of varying numbers of a 56-bp tandemly repeated sequence and a 46-bp insertion/deletion (indel). The structure and organization of this segment is similar to that of other teleost fish and vertebrates. However, extensive variation in the copy number of tandem repeats (0–5 copies) and the presence of a relatively large (46-bp) indel, are apparently uncommon in teleost fish control region sequences reported to date. The common occurrence of tandem arrays in fish control regions could be related to a stable secondary structure. Based on the frequency distribution of tandem repeat units, no significant geographic heterogeneity (P=0.904) among eight populations of Japanese Spanish mackerel was detected by the exact test. Long period of larval stage, strong dispersal ability of adults and long migrations might be responsible for the high genetic connections among populations and reducing the genetic heterogeneity.