Assessing the status of endangered invertebrates from the ancient Lake Ohrid: The gastropod Chilopyrgula sturanyi

Lake Ohrid is the oldest and deepest lake on the Balkan Peninsula and one of the five oldest lakes in the world. Two of the most striking attributes of the species of the Lake’s fauna, especially the fauna of gastropods, are the high level of biological diversity as well as a high percentage of endemism. The main subject of interest in our research was to follow the distribution and density of the endemic gastropod species Chilopyrgula sturanyi. For this purpose different depth points of the transect Hydrobiological Institute-Radozda as well as other littoral points on the northwestern part of Lake Ohrid, were investigated. The results showed maximum density in the population of Chilopyrgula sturanyi in the muddy lakebed covered by Chara tomentosa. The minimum density in population was recorded on the lakebed with gravel. Specimens of Chilopyrgula sturanyi were not recorded at the depth of 50 m, where the lakebed is covered by a sandy-muddy substrate