The ultraabyssopelagic is the layer of water that covers the deepest parts of the seabed, at depths greater than 6,000 metres. The ultraabyssal fauna is qualitatively very rich. More than 60% of the species are endemic. The most abundant are invertebrates: actinia, polychaetes, crustaceans, molluscs, echinoderms, pogonophores, and fish - liparids, erratinids, nudibranchs.