A genetic analysis of wild-caught tetsugyo from Yutori-numa Pond, Miyagi Prefecture, a long-finned fish of uncertain origin designated as a National Natural Monument in Japan, demonstrated that some specimens were hybrids of goldfish (Carassius auratus) and crucian carp (genus Carassius). Phylogenetic analysis of sequences from part of the D-loop region of mitochondrial and nuclear DNA of 87 Yutori-numa tetsugyo indicated that 66 belonged to the goldfish group and 21 to the Japanese crucian carp group, subsequent PCR-RFLP analysis of c-myc gene revealing three different restriction fragment digest profiles, 21 and 60 specimens possessing goldfish or Japanese crucian carp genes, respectively, and the remaining 6, both genes, indicating their hybrid origin.
