Species identification of upstream fatminnow Rhynchocypris oxycephalus and downstream fatminnow Rhynchocypris lagowskii, based on PCR-RFLP of mitochondrial DNA

The morphological similarity between upstream fatminnow Rhynchocypris oxycephalus and downstream fatminnow Rhynchocypris lagowskii makes it difficult to discriminate accurately between these species in rivers where they coexist. For easy and precise identification of these two species, we developed a genetic discrimination method based on PCR-RFLP analysis for specimens from the Inohzawa River watershed in the Izu Peninsula, central Honshu, Japan. This genetic method was applied to the species identification of the fatminnows from two other watersheds, the Kano and Kawazu Rivers, flowing across the peninsula from north to south. We present the genetic evidence for the restricted distribution of R. oxycephalus and the ubiquitous distribution of R. lagowskii in the peninsula.