New species Eutobrilus gagarini sp. n. and a review of species of the genus Eutobrilus from graciliformis-group (Nematoda: Tobrilida, Tobrilidae, Eutobrilinae)
A new species of Eutobrilus gagarini sp. n. from the Leningrad region is described, which is included in the morphological graciliformis-group of the genus Eutobrilus and differs from other species of the group by a high coefficient “b” and a smaller ratio of the length of the spicules to the length of the supplementary row and the ratio of the length of the spicules to the length of the body. A key for determining the Holarctic species of the graciliformis- group is given and the composition and structure of this group as a whole are discussed. The expediency of isolating the morphological graciliformis-group is discussed. The synonymization of the genus Peritobrilus Gagarin, 1993 with the genus Eutobrilus Tsalolikhin, 1981 is confirmed.