Eucyclops delongi sp. nov. (Cyclopiformes: Copepoda: Crustacea) from the River Lena delta, Polar Eastern Siberia, Russia

A new species of Eucyclops (Cyclopiformes: Copepoda: Crustacea) is described from a bog-lake on the top of a hill near Titary fisherman village in the top of The River Lena delta, Eastern Siberia, Russia. Eucyclops delongi sp. nov. belongs to the speratus group of species and can be clearly separated from other related species by a combination of characters that include smooth hyaline membrane on 3 distal segments of antennule, missing of long hairs on antenna basipodite posterior surface (on the top), presence of several long setules on the distal side of the caudal rami (saw), homogeneous hair row on both sides of inner coxal spine in 4th swimming legs, relatively short caudal rami (length/width ratio less than five), clearly seen difference in caudal saw denticles on lateral edge, very long innermost caudal seta subequal to ramus length, inner spine of distal segment of endopodite 4th swimming leg 1.1 times as long as segment itself. Male of new species can also be separated from other species by a combination of the following characters: antenna basipodite on posterior surface without groups of long hairs (on the top), coxal spine of 4th swimming legs homogenously covered with long hairs, rudimental 5th legs with relatively short inner spine similar in length to segment itself, rudimental 6th legs with 3 appendages including strong inner spine reaching the middle of the next segment, outer seta as long as spine, middle seta is shorter than spine. This species is suggested to be an endemic of Arctic zone in Eastern Siberia (Beringia), which is well known as a Pleistocene refuge during glaciation in North-East Asia.