is considered one of the most useful markers for comparative evolutionary and phylogenetic studies. In this study, the first internal transcribed spacer (ITS1) region was analyzed using female and their hybrids to explore their genetic characteristics. The results indicated that the intraindividual and interspecific polymorphism levels P. dentatus P. olivaceus and the hybrids. No recombinants were identified in the parental ITS1 sequences. However, four type X and Y sequencerecombinants were identified in the hybrids, suggesting that there was a higher likelihood of forming recombinants in the hybrids than in the parental ITS1 sequences. Further analyses using Kimura 2-parameter distance showed that the genetic distance between the hybrids andP. dentatus (0.018). In the hybrids, the frequency of Type X (85.5%) was considerably larger than that of Type Y (8.7%), indicating that the genetic material from both the male and the female parent was inherited by the offspring and that from the male parent had a considerable advantage. Hence, the molecular evidence indicates that the offspring were derived from hybridization between , rather than from any other breeding method. This study aimed at analyzing the polymorphism of ITS1 sequences and providing useful data for fish ribosomal DNA.