Oligochaetes in southern European groundwater: new records and an overview

This work deals with an overview of the faunal composition and presents a general ecological approach to the groundwater oligochaetes in southern Europe. The species richness is high and similar to that of the superficial waters in the same area. Among the 150 species that we found, about 29 are stygobiont, so the total number of stygobiont species in the area studied has been increased to 58. Ten of these species are tubificids with marine phyletic affinities. A list of the most frequently found species and the relative abundance of the different families and genera collected in the main environments investigated are presented. Although enchytraeids often dominated the fauna, lumbriculids and tubificids exhibit a high level of diversity and comprised the majority of stygobiont and stygophilous taxa found. The discovery of members of the family Parvidrilidae in southern European caves is the first outside of North America. This indicates that the family is widely distributed in the Palearctic region and typical of underground waters. Here, we update the previous evaluation of the knowledge about oligochaetes inhabiting groundwater: 96 species of stygobiont freshwater oligochaetes (sensu stricto) are now known in the world and 81 of them have been recorded from the Palearctic region.