Зимовка гусеобразных Anseriformes на Командорских островах: современное состояние и исторический обзор.

New data and analysis of changes in the number of wintering Anseriformes on the Commander Islands, the northernmost wintering site in the Far East, are presented. The surveys were carried out in March 2015-2019, mainly overland and covering 61 % of the coast of Bering Island, with 100 % of the coast in 2015 as an exception. Boat surveys of A. canagicus were carried out separately in the southwestern part of the island in April. In total, 17 species were encountered, including 12 recorded regularly, and 5 not annually. On Medny Island, the survey was carried out once, on April 3-4, 2017, by boat, and covered the entire coast. There, 7 species were taken into account. The total number of wintering Anseriformes of the Commander Islands is about 21 thousand birds, including 18.5 thousand on Bering Island and 2.5 thousand on Medny Island. The majority is concentrated in the northern and central part of Bering Island; in the south, the number is much lower. The dominant species is H. histrionicus: 65-72 % on Bering Island and 63 % on Medny Island. Subdominant is P. stelleri (16-20 % on Bering Island) as well as S. mollissima (30 % on Medny Island). The density of birds in the northern and central parts of Bering Island is 90-111.5 individuals per km of the coastline; in the south of the island, there are about 12 individuals; and on Medny Island, 14.9 individuals per km of the coastline. Over the past 25 years, the numbers of A. canagicus, A. platyrhynchos, A. acuta, B. clangula, and M. serrator have increased. P. stelleri and C. hyemalis have decreased. A. penelope, M. americana, and B. albeola began to regularly occur at the wintering, and B. bernicla, A. crecca, and A. marila have been observed more often than before. M. deglandi and M. merganser are now more common during migration, and practically are not observed at the wintering.

Unusual Structures and Cytotoxicities of Chitonoidosides A, A1, B, C, D, and E, Six Triterpene Glycosides from the Far Eastern Sea Cucumber Psolus chitonoides

Six new triterpene tetra-, penta- and hexaosides, chitonoidosides A (1), A1 (2), B (3), C (4), D (5), and E (6), containing one or two sulfate groups, have been isolated from the Far-Eastern sea cucumber Psolus chitonoides, collected near Bering Island (Commander Islands) from the depth of 100–150 m. Three of the isolated compounds (1, 3 and 6) are characterized by the unusual aglycone of new type having 18(20)-ether bond and lacking a lactone in contrast with wide spread holostane derivatives. Another unexpected finding is 3-O-methylxylose residue as a terminal unit in the carbohydrate chains of chitonoidosides B (3), C (4), and E (6), which has never been found before in the glycosides from holothurians belonging to the Psolidae family. Moreover, this monosaccharide is sulfated in the compound 4 into unprecedented 3-O-methylxylose 4-O-sulfate residue. Chitonoidoside C (4) is characterized by tetrasaccharide moiety lacking a part of the bottom semi-chain, but having disaccharide fragment attached to C-4 of Xyl1. Such architecture is not common in sea cucumber glycosides. Cytotoxic activities of the compounds 1–5 against mouse and human erythrocytes and human cancer cell lines: adenocarcinoma HeLa, colorectal adenocarcinoma DLD-1, and leukemia promyeloblast HL-60 cells were studied. The cytotoxic effect of chitonoidoside d (5) was the most significant in this series due to the presence of pentasaccharide disulfated sugar chain in combination with holostane aglycone. Surprisingly, the glycosides 1 and 3, comprising the new aglycone without γ-lactone, demonstrated similar activity to the known compounds with holostane aglycones. Chitonoidoside C (4) was less cytotoxic due to the different architecture of the carbohydrate chain compared to the other glycosides and probably due to the presence of a sulfate group at C-4 in 3-O-MeXyl4.