Vol 102, No 5 (2023)

Two decapodite stages of the shrimp, Argis lar, family Crangonidae, from the plankton off the Kronotsky Bay, northwestern Pacific, eastern Kamchatka, are described. Сomparison of The available larvae were morphologically compared with decapodites of other species of this family with a shortened development. The first and second decapodite stages were similar in size and structural features of the pleon, carapace, antennae, mandibles, maxillae, pereiopods, and pleopods. Significant differences were found in the morphology of the telson, maxilliped, and antennules in the first and second decapodite stages of A. lar. In the second decapodite stage, the posterior median spine shifted to the middle of the carapace, the number of antennular and maxilliped endopod segments were increased, the epipodite appeared in the third maxilliped, the shape of the telson changed, the terminal spines in the telson disappeared, and the relative length of the angular setae were decreased. Kuro shrimps are thought to have three to five larval stages.

In July 2018, diving beetles were collected in the most typical water bodies and other habitats in the vicinity of Amderma, Kara Sea coast, northern Yugorsky Peninsula. The fauna comprises 15 dytiscid species from 7 genera. The most diverse genera were Agabus and Hydroporus. The record of Dytiscus lapponicus was the northernmost for this species, while the reports of Hydroporus cf. fuscipennis and Agabus pallens were the northernmost for the Palaearctic parts of their distribution ranges. Original photographs illustrate peculiar specimens of Dytiscus lapponicus with dark head, pronotum and scutellum. Most of the species show vast Holarctic Arcto-Boreal or Arcto-Boreal-Montane distributions. The species composition of the Dytiscidae is quite similar to those of the northernmost mainland regions of the European Northeast (Pakhancheskaya Bay, Kara Tundra and Pamal), as well as the Vaigatch and Dolgyi islands, being less similar to those of the south tundra regions (Kanin Peninsula, Bolvanskaya Bay and Antipayuta village, Gydan Peninsula). Among the study habitats, the most diverse beetle assemblage inhabited thermokarst lakes (up to 14 species, the maximum density noted was 1150 ind./100 trap-days). On the contrary, on salt marshes, only 2–3 beetle species were recorded and the total abundance was significantly lower (1.8–3.6 ind./100 trap-days).

In an intermontane kettle at the southwestern spurs of the Bureinsky Mountain Range, in the Bureya River basin, the Ussuri white-toothed shrew has been recorded for the first time. This locality lies north of the previously supposed species distribution range in the south of the Russian Far East. The study of the female karyotype has allowed us to describe the morphology of the chromosomes of Crocidura lasiura (2n = 40, NF = 54). The karyotype differs from the earlier published information (2n = 40, NF = 56) on the number of subtelocentric autosomes. The data obtained expand the northern range limit of the Ussuri white-toothed shrew and show variability in the number of chromosome arms (NFа = 50, 52).

Geographic variations in the shape of the upper cheek toothrow were studied using geometric morphometrics. For this, 288 specimens from 19 localities (North America, Eurasia, and Pacific and Arctic islands) were employed. Monomorphism of the toothrow for mainland foxes, both from North America and Eurasia, as well as the foxes from Greenland and St. Lawrence Island was found. The Arctic foxes of four Pacific island populations, i.e. two from the Commander Islands and two from the Pribilof Islands, differ significantly from the mainland counterparts in toothrow shape. The Arctic foxes from the Mednyi Island, the Bering Island and the Pribilof Islands differ from each other by toothrow shape as well. The Mednyi Island Arctic foxes show the shortest toothrow, a wide hard palate, and the most massive teeth. On the contrary, the Pribilof Islands Arctic foxes are the most small-toothed. Allometry does not affect geographic variations in the shape of the Arctic fox toothrow. High-level fluctuating asymmetry is found in the Mednyi Island and St. George Island Arctic foxes. Most probably the high level of fluctuating asymmetry is conditioned by both the extremely low genetic diversity as the result of a dramatic numbers decline in the recent past and the strong impact of heavy metals as the result of a coastal diet. We suppose that the same reasons. i.e. low genetic diversity and coastal diet, could have determined the high level of fluctuating asymmetry of the Arctic fox toothrow on the St. George Island.