RECONNAISSANCE OF OSTRACODES IN THE FRASASSI CAVES AND ADJACENT SULFIDIC SPRING AND SENTINO RIVER IN THE NORTHEASTERN APENNINES OF ITALY

Rich, diverse assemblages comprising a total of 21 ostracode species belonging to 15 genera were recovered from phreatic waters of the giant hypogenic Frasassi cave system and the adjacent Frasassi Sulfidic Spring and Sentino River in the Marche region of the northeastern Apennines of Italy. Approximately 6900 valves were recovered from ten sites, eight of which were in the phreatic waters of the cave system and sampled at different times of the year over a period of five years. The most abundant species in the sulfidic spring and Sentino River were Prionocypris zenkeri, Herpetocypris chevreuxi, and Cypridopsis vidua, while the phreatic waters of the cave system were dominated by two putative new stygobitic species of Mixtacandona sp. and Pseudolimnocythere, and a species that was also abundant in the sulfidic spring, Fabaeformiscandona ex gr. F. fabaeformis. Pseudocandona ex gr. P. eremita, likely another new stygobitic species, is recorded for the first time in Italy. The relatively high diversity of the ostracode assemblages at Frasassi could be attributed to the heterogeneity of groundwater and associated habitats or to niche partitioning promoted by the creation of a chemoautotrophic ecosystem based on sulfur-oxidizing bacteria. Other possible factors are the geologic age and hydrologic conditions of the cave and karst aquifer system, which possibly originated in the early–middle Pleistocene when topographic uplift and incision enabled deep sulfidic waters to reach the local carbonate aquifer. Flooding or active migration would have introduced the invertebrates that now inhabit the Frasassi Cave system.