The samples were collected during a hydrobiological survey of the compex expedition of KUBZ (Moscow Zoo young biologist's coterie) in August, 2014. Microcrustaceans were collected from 21 freshwater habitats from south­western part of Shokalsky Island, most of them were small thermokarst ponds with the depth of 0.5­ - 1.5 m (Fig. 2). Environmental variables such as bottom sediment type (clay, silt, sand, detritus or thick mosses, measured in accordance with Wentworth Grade Scale (Ongley 1996)), average depth (mean value for the whole sampled area) and size (average length of diameters) of the water body were noted for each site (Table 1). The sampling was performed from the shore using a qualitative plankton net (type “Apstein”, mesh size 50 μm). Upon collection, all samples were preserved in ethanol (96%). Species identification and enumeration was carried out primarily in Bogorov counting chambers; the total numbers of Cladocera and Copepoda were recorded. Description of the distributional ranges of the species is also provided in the checklist: AT - Afrotropical, AU - Australasian, ANT - Antarctic, NA - Nearctic, NT - Neotropical, OL - Oriental, PA - Palaearctic, PAC - Pacific oceanic islands.

Figure 2.  

Location of the sampled stations in inner water bodies on the map of Shokalsky Island (Google Maps).

In total 15 species of microcrustaceans were identified, comprising 12 species in 12 genera of Cladocera, and three species in three genera of Copepoda. All of the taxa have not been previously documented on the island. Microcrustaceans were found in 90% of the studied sites. The number of species encountered in each water body varied from one to ten (Table 2). The most common species in the studied sites were Leptodiaptomus angustilobius (Sars, 1898), Polyphemus pediculus (Linnaeus, 1761) and Chydorus cf. sphaericus (Muller, 1776), they usually dominate in the communities and occured in most of the investigated water bodies.

The distributional ranges of all the species are rather wide, none of them are restricted to the arctic area or more limited region. The areas of the species are noted in the Checklist according to the FADA Databases of Cladocera (Kotov et al. 2013) and Copepoda (Boxshall and Defaye 2009). The most important findings are Latona setifera (Muller, 1776), Diaptomus cf. castor (Jurine, 1820) and Graptoleberis testudinaria (Fischer, 1848). The first two species have never been found on the territory of Yamalo-Nenets Autonomous Okrug, and the third one was only known from waters of lower Ob' River (Semyonova et al. 2000). All of them occured rarely in separate water bodies. For the species L. setifera this record is the northernmost finding ever (Korovchinsky 2004).