An Investigation into the Diversity of Leeches (Hirudinida) in the Baltic States

Abstract

The Baltic states—Estonia, Latvia, and Lithuania—are situated on the eastern coast of the Baltic Sea between Russia and the Scandinavian countries. This region is characterized by diverse landscapes and numerous bodies of water, including lakes, peat bogs, and marshes, which serve as natural habitats for aquatic invertebrates, including leeches. Despite the rare and uncertain taxonomic status of leech species in the area, research in the Baltic region has been inadequate. Therefore, this study aims to examine the composition of leech species in the Baltic countries, drawing on both past and current research. The study also seeks to assess the status of Hirudo medicinalis in the Baltic region and discuss the rare, questionable, and potentially present leech species in the Baltic states. A scoping review method was employed, surveying published references, books, and databases. In total, the study found records of 21 leech species in Estonia, 15 in Latvia, and 26 in Lithuania, belonging to the families Glossiphoniidae, Erpobdellidae, Hirudinidae, Haemopidae, and Piscicolidae. Hirudo medicinalis L. is distributed throughout all Baltic countries, but the most recent records on their location are only available for Estonia. The data on a few Piscicolidae species is questionable and requires verification, but further research on Piscicolid leeches can potentially lead to the discovery of rare species.