New genus and species of the deep-sea family Coronarctidae (Tardigrada) from a submarine cave with a deep-sea like condition.

A new genus and species of the deep-sea family Coronarctidae (Tardigrada, Arthrotardigrada), collected from a sublittoral submarine cave in the French Mediterranean Sea, is described and illustrated. Tardigrades were only present in the first centimetres of the cave sediment(1.5-2 cm), where the 80 % of meiofauna, largely dominated by nematodes, is also concentrated. Trogloarctus trinyches gen. et sp. n. was only identified at the stations with complete darkness, mainly at the far end station. The new genus Trogloarctus shows several characters, distinguishing it from all known Coronarctidae: presence of only one somatic cirrus (cirrus E), three claws on each leg (reduction), and an absence of large accessory spine on the fourth pair of legs. The presence of bar shaped placoids in the pharyngeal bulb may be regarded as a plesiomorphic character. These differences involve the modification of the previous diagnosis of the family Coronarctidae in order to accommodate the new genus Trogloarctus. Ecology and geographical distribution of Coronarctidae is reviewed.