Genus Mesobiotus Vecchi, Cesari, Bertolani, Jönsson, Rebecchi & Guidetti, 2016 Mesobiotus sp. (Fig. 6). Location 2, one juvenile specimen; location 4, 13 eggs. Morphology of the specimen and the eggs are typical for the genus Mesobiotus, M. harmsworthi (Murray, 1907a) morphogroup (according Kaczmarek et al. 2020). Sequences of four markers were obtained for the single specimen and three eggs: 18S rRNA, 28S rRNA, ITS-2, and COI (see Table 3). Homology comparison of the obtained sequences with GenBank records (5 th July 2025) indicated similarity to the genus Mesobiotus. Despite the fact that the single specimen and the eggs were collected in different locations (which though belongs to the same waterbody), they were considered conspecific because of the similarity of the COI gene sequences (uncorrected p -distances between the juvenile specimen and the eggs is 2.4%, which is within the limits of intraspecific variability for tardigrades). The range of uncorrected genetic p -distances for COI and ITS-2 sequences between the studied specimens and sequences of the genus Mesobiotus available in GenBank are presented in SM.05. Considering the significant genetic distance for the COI sequences from all known Mesobiotus species (the closest is Mesobiotus bockebodicus Atherton, Hulterström, Guidetti & Jönsson, 2025 from Sweden; PQ365776; Atherton et al. 2025, p -distance is 19.8%), this is a new species of the genus Mesobiotus. This conclusion was supported by the results of the bPTP species delimitation (see SM.06).

Published as part of Tumanov, Denis V., 2026, Set to its place: first DNA data on freshwater tardigrades of Sakhalin (Far East Russia) shed light on the phylogenetic position of Mixibius (Eutardigrada: Hypsibioidea), pp. 87-108 in Zootaxa 5750 (1) on pages 94-95, DOI: 10.11646/zootaxa.5750.1.4, http://zenodo.org/record/19170183