Abstract: One of the many effects of global environmental change caused by humans is the spread of invasive species. Invasive species can change the entire ecosystem by consuming native species, hybridizing with them, and even competing with them for resources, leading to a decline in biodiversity. Another problem that ensues is the introduction of small foreign organisms, such as parasites and microbes that live inside or outside of other organisms and are difficult to detect. These small, introduced organisms can be vectors of disease, and even if the parasites are native, they are equally problematic if they use both exotic and native species as hosts. Therefore, reports of undocumented parasites and information about their hosts are important to consider when dealing with invasive species issues. On July 24, 2022, several unidentified leeches were found in the carapace and breastplate of wild reeves’ turtles living in the reservoir in Gurye-gun, Jeollanam-do. The leeches shared morphological similarities with a leech species discovered in red-eared sliders in 2020. After recording the date, location, population, and host information of the individuals, we observed their morphological features such as body shape, annulation, and eyes for species identification. We then used the COI gene for genetic analysis. We determined that the leech belonged to the family Glossiphoniidae based on its morphological and genetic traits, cub-raising behavior, and parasitism on freshwater turtles. However, a BLAST comparison of the COI sequence obtained by PCR revealed at least a 10% difference from other Glossiphoniidae species recorded in the NCBI, and the morphological traits also differed from previously recorded species. The leeches found in Jinju and Gurye are most likely members of the same species not only because they share similar morphological characteristics but also because their COI similarity is as high as 99.4%. If the leech was foreign, it might have been introduced from North America where the red-eared slider is the origin, which could be problematic given that it is a tiny, unrecorded invasive species. Since these leeches have been found on both invasive and native species, further research on their introduction routes and ecological characteristics is necessary to assess the impact between these two groups of species. This study highlighted the problems that parasites of such invasive species can bring through the case of discovering a new species of leeches. This will help better comprehend the effects of invasive species on the local environment.
