An annotated checklist of groundwater Cyclopoida and Harpacticoida (Crustacea, Copepoda) from Romania with notes on their distribution and ecology

Romania, by its position in East-Central Europe has a complex geological history, high landscape heterogeneity and variable climatic conditions, ranging from temperate-continental in the northeast to sub-Mediterranean in the southwest. These conditions have created repeated waves of colonisation of groundwater by copepods, which raise particular interest in this group from a biogeographical perspective. The earliest investigations on groundwater copepods, dating back to the beginning of the 19th century, have resulted in a wealth of information on the richness of this group, making Romania one of the best studied regions from this perspective in Europe. Groundwater copepods in Romania are currently represented by 107 species and subspecies, of which 60 are harpacticoids (56%) and 47 are cyclopoids (43.9%). Of these, 50.5% are strict stygobites (32.7% harpacticoids and 17.7% cyclopoids). Among stygobite copepods 29 species (35 harpacticoids and 19 cyclopoids) are endemic to the country. Almost 86% of the species are single-site endemics (single cave, or single hyporheic or phreatic site) and the rest are restricted in distribution to a single aquifer or hydrographic basin. The aim of the present checklist represents a significant contribution to the knowledge of groundwater copepods in Romania and provides a sound baseline for future comparative faunal studies focused on the affinities and origins of copepods and the analysis of their biogeographical distribution patterns at regional and continental scales.