Two New Species of Bipaliinae Land Planarians (Platyhelminthes, Tricladida, Geoplanidae) From the Republic of Korea, Based on an Integrative Taxonomic Approach

Abstract

Land planarians (Platyhelminthes, Geoplanidae) in the Republic of Korea have long been an overlooked taxonomic group, with no formal studies conducted for over a century. Only two species, Diversibipalium koreense and Microplana unilineata, both described in 1923, have been previously recorded. However, their exact type localities remain uncertain, and no subsequent confirmed records have been reported since their original descriptions, making their current taxonomic status uncertain and in need of reassessment. Here, we present the first taxonomic study of Korean land planarians in over 100 years. By combining morphological and molecular data, we propose two new species of Bipaliinae, Bipalium gwangneungensis sp. nov. and Novibipalium koreanum sp. nov., collected from multiple administrative regions in the Korean Peninsula. Bipalium gwangneungensis sp. nov. is unique for its dorsum color, ranging from beige to gray-beige, a horizontally running unpaired portion of the sperm ducts, a penis papilla located dorsally to the common atrium, and the relative length of the copulatory apparatus, with the portion anterior to the gonopore (male) being 1.4 times as long as the posterior portion (female). Additionally, the female genital canal is elongated and inclined ventroanteriorly toward the gonopore. In contrast, Novibipalium koreanum sp. nov. is distinguished by its dorsum, which is ornamented with three or five black longitudinal stripes, a penis bulb located anterior to the penis papilla, and shell glands opening along the proximal, dilated portion of the female genital canal. Phylogenetic analyses of concatenated (18S rDNA, 28S rDNA, and COI mtDNA) and single-gene datasets robustly support the monophyly of each new species, providing strong evidence for the validity of our species delineation. Our study highlights the need for further taxonomic research on this historically overlooked invertebrate group in the Republic of Korea.