Insights into the Eucyclops graeteri species complex (Copepoda, Cyclopidae) — the case of sulphidic groundwaters of Mangalia (Southern Dobrogea, Romania)

Members of the Eucyclops graeteri species complex are widely distributed in European groundwaters and share some morphocharacters such as: a long aesthetasc on ninth segment female antennula, short or very reduced spinule row ("serra") furcal rami, lateral hairiness 5th thoracic somite strongly reduced, few no hairs distal margin intercoxal sclerite 4th legs pair. All these characters subject to strong selective pressure underground environment; therefore, study molecular markers is needed better define taxonomy phylogeny this group. The Southern Dobrogea region Romania conceals dark, isolated, sulfide-rich aquifers, accessible through artificial wells, springs, Movile Cave. chemoautotrophically-based Cave hosts member E. complex, described several years ago as subspecies ( scythicus Plesa, 1989). morphological analyses performed specimens collected from revealed new records for both sulfidic non-sulfidic wells dug near cave well putatively science three Mangalia. Mitochondrial allocated population distinct clade within genus , serrulatus s.l. being closest taxon. putative belongs different subfamily Eucyclopinae, raising doubts monophyly complex. Furthermore, our investigations occurrence ectosymbiont sulfur-oxidizing Thiothrix bacteria associated with suggesting that symbiosis could allow taxon cope sulphidic-rich environments. These unique groundwater environments therefore provide an interesting model system which copepods their adaptation harsh environmental conditions.