Marine and anchialine caves host specialized faunal communities with a variable degree of endemism and functional specialization. However, biodiversity assessments on this habitat are scarce, particularly in relation to small-sized cryptic fauna (such as amphipods), which often play a key role in benthic ecosystems. The present article compiles all records of marine and brackish-water amphipods inhabiting marine and anchialine caves along the Mediterranean basin, combining information extracted from a literature review with newly acquired records. A total of 106 amphipod species has been reported (representing approximately 20% of the Mediterranean amphipod species), mostly from the North-Western Mediterranean. Examination of new material from marine caves in Greece has yielded 14 new records from the East Ionian and Aegean Sea. Most of the reported species display wide ecological amplitude in terms of habitat and substrate preferences, feeding habits as well as bathymetric and geographical distribution. In contrast, only 17 amphipod species have been reported from marine-brackish waters in anchialine caves, predominantly represented by cave specialists with a narrow spatial distribution and distinct morphological traits. Our overall knowledge on amphipods inhabiting Mediterranean caves is far from complete so that new and valuable findings are expected to occur as new caves are explored.
