摘要：The Ogulin cave sponge (Eunapius subterraneus Sket & Velikonja, 1984) is the only known freshwater sponge (family – Spongillidae) among stygobionts in the world. There are two registered subspecies: the type Ogulin cave sponge (E. s. subterraneus Sket & Velikonja, 1984) and the Rudnica cave sponge (E. s. mollisparpanis Sket & Velikonja, 1984). This paper considers morphological features of the species, its distribution and hydrogeological relations in the Ogulin area. Each locality is presented in the article through its geographical position, a short description and a topographic map. Two different sponge morphotypes are observed: the egg-shape and the plate-shape. The sponge is registered at six localities, one in the Lika region, on the other side of Velika Kapela Mountain and the remaining ones in the surroundings of the town of Ogulin. The Ogulin cave sponge can be found at five localities and the Rudnica cave sponge at only one, Rudnica VI Cave. The type subspecies is found in the subterranean waters of the rivers Dobra, Tounjčica and Zagorska Mrežnica, whereas the Rudnica cave sponge lives only in the spring of the River Rudnica. All populations have been found in groundwater habitats. There is only one locality where they are exposed to daylight. They tend to inhabit walls outside of strong currents, but also considerably big rocks, mostly their underside. Other explorers also observed in their earlier research sponges in the Đula - Medvedica cave system and Špilja Cave u Kamenolomu Tounj. However, during the last explorations those populations were not found, and their taxonomical status has remained unknown. The Ogulin cave sponge is one of the numerous subterranean animals living in the Ogulin underground waters that are extremely endangered by human activities. Preservation of the Ogulin subterranean passages is vital not only because of its unique fauna, but also because the world’s sources of clean and drinking water have been decreasing in number.
