Nematodes in caves: a historical perspective on their occurrence, distribution and ecological relevance

Caves and cave-dwelling biota have fascinated scientists for centuries. Nevertheless, there is a considerable lack of information on subterranean realms and the ecosystems they host. Nematoda, for example, is a group of invertebrates that plays an important role in the functioning of epigean ecosystems, but whether or not the same is true for subterranean ecosystems remains unknown. For this reason it was decided to conduct an in-depth review of all reports related to cave-dwelling nematodes in order to provide a sound basis for future studies. A literature survey of 41 scientific works from over the last 138 years revealed 295 unique taxa reported from 78 different cave systems. The historical trends in cave nematology, peculiar findings from important studies and an ecological classification system are discussed. Lastly, the trophic distribution of the reported taxa is presented, whilst nematodes from other (non-cave) subterranean environments are also considered.