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The morphological variability, distribution patterns and endangerment in the Ogulin cave sponge Eunapius subterraneus Sket & Velikonja, 1984 (Demospongiae, Spongillidae)

The distribution and morphological variability of the troglobiotic freshwater sponge Eunapius subterraneus Sket & Velikonja, 1984 registered in Croatia as a threatened species in the IUCN category Endangered (EN) was investigated. The research area encompassed Velika and Mala Ka-pela Mountains as well as the upper catchment area of the Dobra and Mreznica rivers on the NE side of Velika and Mala Kapela Mountains, mostly in the Ogulin-Plaski karst plateau. The species was registered in six localities, three previously known from the literature and three constituting new records: Mandelaja pit and the caves Crnacka spilja and Izvor spilja Gojak. For subspecies identification the morphology and dimensions of megascleres and gemmuloscleres of the collected samples were analyzed. Significant differences among sponge populations were indicated by one--way ANOVA (p < 0.001) in width and length of megascleres. The subspecies E. s. mollisparspanis Sket & Velikonja, 1984 was found only at its type locality, in the cave Rudnica spilja VI. The preliminary variability of other populations after discriminant function analysis of measured mor-phometric parameters such as the width and length of mega- and gemmulo-scleres indicates four groups, but it was not possible to separate them clearly in all cases. Subterranean sponges were not found in two localities known from the past, the Dula - Medvedica cave system and the cave Spilja u kamenolomu Tounj, both under great pressure of groundwater habitat changes because of water pollution, river direction changes and habitat destruction.

freshwater sponges ; caves ; springs ; gemmules ; spicules ; distribution ; Croatia

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