Dugesia japonica is a species of freshwater planarian that inhabits freshwater bodies of East Asia, including Japan, Korea, Taiwan, China and northeastern Siberia.

[2] However, molecular studies suggest that Dugesia japonica is polyphyletic and different populations across its area of occurrence constitute distinct species.

[3] D. japonica position in relation with other Dugesia species after the work of Lázaro et al., 2009:[4] D. sicula D. aethiopica D. japonica D. ryukyuensis D. notogaea D. bengalensis D. subtentaculata D. gonocephala D. liguriensis D. etrusca D. ilvana D. benazzii D. hepta A study was published in 2017 in which a Dugesia Japonica trunk fragment had been sent into space, and grew with two heads, one on either end of the trunk.

[5] However, the influence of space conditions on this phenomenon is debated.

[6]