Article ID: 24-033
The native range of “Type I” mitochondrial DNA (mtDNA) of the dojo loach (Misgurnus anguillicaudatus complex), originating from M. sp. Type I sensu Okada et al. (2017), is found only in Japanese native dojo loach populations on the eastern Pacific and central-north Japan Sea regions of Honshu Island. However, a stand-alone distribution of Type I mtDNA was recently reported from a few individuals in a single dojo loach population in Nagoya City, Aichi Prefecture, located in central Honshu Island. Genetic analyses on 54 individuals (out of 81 collected from the population) were conducted to clarify the strict phylogenetic position of Type I mtDNA and the genetic population structure. Genetic screening and sequencing analyses targeting the Cytb gene region revealed a single common Type I haplotype in only four individuals. Although the independent phylogenetic status of the haplotype among Type I haplotypes from the entire native range was confirmed, it was clustered with known Type I subclades detected from the west side of the Fossa Magna region. Such genetic independence and its relationship to geographical proximity indicated that the haplotype was native to that region. Nuclear DNA analysis targeting the IRBP2 and RAG1 gene regions revealed that most individuals were hybrids among three groups comprising the detected mtDNA (Type I and Types IIa and IIb, originating from Japanese native and Chinese clades of M. anguillicaudatus). Four individuals carrying Type I deviated significantly from random mating with individuals carrying other mtDNA types, and two individuals with notable morphological characteristics of M. sp. Type I (including genetic factors associated with M. sp. Type I in both mitochondrial and nuclear DNA) indicated that M. sp. Type I had maintained its genetic integrity in the presence of the other two groups.
