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The study presents new data on the structural and functional organization of the mesonephros of the grayling Thymallus thymallus (Linnaeus, 1758). Adult grayling were sampled in the middle course of the Unya River, a tributary of the Pechora River (Komi Republic, Russia). The mesonephros of the grayling, as of other freshwater fishes, is composed by nephrons, blood vessels and hematopoietic tissue forming the renal interstice. In the interstice, сells with a radial vesicle array and chloride cells were discovered; the latter were mostly localized near the renal tubules. The degree of the interstice development in the mesonephros of the grayling was determined. New data on the ultrastructure of leukocytes, cells with a radial vesicle array, chloride cells, and nephron segments were obtained. A lack of mesangial cells, a small number of podocytes, and a thin basement membrane were observed on the sections of a renal corpuscle, being characteristic features of the ultrathin organization of the mesonephros in freshwater members of Salmoniformes and Esociformes. In the grayling’s nephrons, no neck segment was found, which was reported earlier for several species, including mammals. On the sections of proximal tubules, the ciliated cells were rare, and large amounts of the tubular-vesicular network in the zone of endocytosis of the type II epithelial cells were observed. On the sections of distal tubules, short blade-shaped cytoplasmic processes, with large numbers of invaginations of cytoplasmic membrane, were found. On the basis of the distinctive ultrastructure features mentioned above, the inference that grayling show the cytological markers of adaptation to euryhalinity was made. Thus, the results contribute to the knowledge of mesonephros development in fishes during their life history. From the species protection standpoint, our study provides baseline data on a WBC differential in the mesonephros as well as superoxide dismutase, catalase, glutathione S-transferase, and ethoxyresorufin-O-deethylase activities, which can be used in further studies addressing the health status of grayling populations.

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The paper is based on the dataset whose purpose was to deliver, in the form of GBIF-mediated data, diverse materials on the biodiversity of a large mire, Shichengskoe mire (Vologda Region, north-western Russia), including its various mire sites and intra-mire water bodies. The dataset was based on our materials collected for two decades (from 2000 to 2021) in different parts and biotopes of the Shichengskoe mire and complemented by scarce data obtained previously by other researchers. The data contain materials on the diversity of Animalia (2886 occurrences), Bacteria (22), Chromista (256), Fungi (111), Plantae (2463) and Protozoa (131). Within the study period, the most detailed and long-term biodiversity studies were carried out for higher plants and invertebrates. On the other hand, the data on the composition of lichens, protozoa, algae, basidiomycetes, some groups of invertebrates and, to a lesser extent, lichens and vertebrates are far less comprehensive and require further substantial research efforts. The list includes occurrences from both the peatland (mire sites and mire margins different in typology) and the objects of the mire hydrographic network. In a standardised form, this article summarises both already published (mainly in Russian) and unpublished materials. The paper summarises the results of long-term research on the biodiversity of a boreal mire, including its hydrographic network. A total of 5869 occurrences were included in the dataset published in the Global Biodiversity Information Facility (GBIF, gbif.org) for the first time. According to the GBIF taxonomic backbone, the dataset covers 1358 taxa, including 1250 lower-rank taxa (species, subspecies, varieties, forms) and 108 taxa identified to the genus level. Several species found in the Shichengskoe mire, mainly belonging to Bacteria, Chromista and Protozoa, have never been listed in GBIF for the territory of Russia before. The overwhelming majority of occurrences and identified species came from the territory of Shichengskiy Landscape Reserve. Due to our work, this Reserve is now the most studied regional reserve in the Vologda Region with respect to biodiversity. By the number of revealed species, it is close to two federal protected areas: Darwinskiy State Nature Biospheric Reserve and National Park "Russkiy Sever".

The dataset contains microclimate parameters including air temperature, relative humidity and dew point measurements from a large wetland, Shichengskoe mire system, in Vologda Region, Russia, during four vegetation periods. Data were collected in 2013–2015 and 2017 using DT-171 data loggers (Elma Instruments). Data loggers were attached to the wooden posts at 0.5 m height from the surface. Continuous recordings were performed every 30 min providing 48 measurements of air temperature, relative humidity and dew point per day. The dataset presented in the article is of particular value to understanding the heterogeneity of abiotic parameters within mire systems.

Alternation of physiological states during the annual cycle (pre-spawning mobilization, spawning energy loss, post-spawning accumulation of energy reserve, declined metabolic activity during the wintering) occurring in the wide temperature range requires high plasticity of fish defense systems. The article presents a 2-year study of hepatic antioxidant defenses and lipid peroxidation in the temperate cyprinid fish, common bream Abramis brama (L.), in relation to basic annual rhythms, such as photoperiodic and temperature cycling, reproduction and feeding activity. The objective of the study was to evaluate the plasticity of antioxidant defenses in bream under normal conditions throughout the annual cycle, by measuring hepatic antioxidants (superoxide dismutase, catalase, glutathione-S-transferase activities and reduced glutathione concentrations) and products of lipid peroxidation (thiobarbituric acid reactive substances concentrations). The results suggested that hepatic levels of antioxidants in bream varied dramatically during the annual cycle allowing bream to develop necessary adaptation and implement reproduction program. The lowest values of all studied antioxidants were witnessed in the middle of winter. In early spring, antioxidant enzyme activities increased rapidly reaching their maxima in late spring and summer. Toward the end of autumn, enzyme activities were declining toward the levels observed before the ice breakup. Spring-summer up-regulation of antioxidant defenses along with increased lipid peroxidation indicated bream to be experiencing mild oxidative stress.

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