Vol 102, No 9 (2023)

This study was carried out in the littoral zone of Lake Baikal during a large-scale ecological crisis that affected all parts of the ecosystem, including populations of endemic sponges of the family Lubomirskiidae. Sponges play important roles in biotic communities of the rocky littoral of the lake, ensuring water purity and serving as a specialized habitat for a variety of organisms. In the last decade, mass disease and mortality of sponges were reported in different areas of Lake Baikal, which can lead to irreversible changes in the structure of littoral communities. We studied the taxonomic richness, distribution, and abundance of the main groups of macroinvertebrates, such as amphipods and gastropods, living on diseased branched Lubomirskia baikalensis sponges in three basins of Lake Baikal (2015, 2020, 2021, 2022) and made historic comparisons. The taxonomic richness of amphipods, including 35 species or subspecies, as well as further 5 taxa identified only to genus, increased and had 20 taxa more than 30 years ago. A total of 22 gastropod species or subspecies were found on the sponge, 20 of them for the first time. The species composition, dominant species complex and quantitative characteristics of sponge-associated amphipods and gastropods varied in different lake areas as evidenced by underwater observations. The abundance of all macroinvertebrate groups, as well as dominant amphipod and gastropod groups per unit weight of sponges decreased from south to north. The abundance of the invertebrates associated with diseased sponges was similar to the records of the pre-crisis period. Baikal sponges host invertebrates from several ecological groups with different feeding strategies (grazers, scrapers and filter feeders) providing a temporary refuge for most of them. In order to restore the abundance of sponges and preserve the populations of key invertebrate species, we propose to set up sponge “farms” in the least polluted areas of Lake Baikal.

This report is the second of a series devoted to redescriptions of members of Baikalomoraria based on modern research methods. An illustrated redescription of the female and male of Moraria (Baikalomoraria) werestschagini Borutzky 1949, a rare endemic harpacticoid species from the littoral zone of Lake Baikal, is presented. Since the type material of the species was lost, it became necessary to select a neotype. For the first time, the morphology of this species was studied in detail using scanning electron microscopy, and a description of the mouthparts and antennules was given. The description of the swimming legs was significantly supplemented and the structure of the genital field was shown, including data on the morphological variability of limbs. In addition, we briefly describe the fifth copepodite stages of the male and female. The fifth copepodite stage of the female was found to bear long apical setae on the caudal rami, vs adult females characterized by short setae more similar to spines.

Pallas’ spadefoot is a Eurasian species of amphibian that winters for about half a year at a depth to 200 cm, always below the level of freezing, since it does not survive negative temperatures. However, significantly digging into the soil can cause oxygen deficiency. The minimum sufficient for a long-term existence of Pelobates vespertinus and the lethal oxygen content in the air were revealed, as well as metabolic pathways were evaluated under the conditions of normoxia and hypoxia in laboratory experiments. Beside this, the seasonal dynamics of temperatures and oxygen concentrations in sandy loam soils at different depths were determined in a typical wintering biotope of the species (the Oka River valley). Animals have been found to be capable of withstanding a tenfold decrease in oxygen content in soils compared to atmospheric oxygen for more than two months, thereby remaining quite active. When the concentration is decrease 20 times (up to 1%), a state of coma occurs, which is reversible if it lasts not more than a day. This shows a high degree of resistance of the species to stress resulting from reoxygenation and staying in an environment with variable oxygen levels. Thus, P. vespertinus is the second amphibian species following the Siberian frog (Rana amurensis), which can tolerate its complete absence for a long time (several months). Compared to body weight, the spadefoot has small storage organs (fat bodies and liver) and a low content of reserve substances (lipids and glycogen) in tissues, which are usually consumed at a low rate in normoxia at 3°C. During hypoxia, lipid utilisation is suspended and glycogen consumption is increased, indicating a shift from aerobic to predominantly anaerobic metabolism. The cumulative effect of reduced metabolism due to low temperature (3°C) and the activation of glycolysis due to the lack of oxygen provides a high level of resistance to hypoxia, distinguishing Pallas’ spadefoot from other swarming amphibian species studied. The oxygen content in the ground air of typical places at wintering depths (in sandy massifs) is shown to coincide with the atmospheric oxygen. The ubiquitous choice by the species of wintering areas with loose soils is assumed to be associated not with their excellent aeration, but rather with the ease of digging. The results obtained seem to be promising for using the study spadefoot (and possibly other species of the spadefoot genus, as well as burrowing toads) as model for exploring the adaptations to air oxygen deficiency.

Using GPS-GSM trackers, data on the spatial distribution and habitat features during the wintering period were obtained for five young greater spotted eagles (Clanga clanga) tagged in the center of European Russia or the Middle Volga region. The wintering areas of the studied birds, with the exception of one individual in the second and third winters, were located in the Middle East (Israel, northern Egypt, Saudi Arabia, Iran), in South Africa (Sudan and South Sudan), and in Azerbaijan. An uneven distribution of greater spotted eagles in winter territories was revealed, within which the birds spent most of their time in preferred areas where they stayed for long periods. The size and configuration of winter territories depended on the availability of forage lands. Ecological features of the territories caused a difference in the square of wintering grounds and the character of daytime movements of different individuals. The bird wintering in the arid landscapes of the Arabian Peninsula with extremely poor forage conditions was forced to make maximal daily movements in search of prey. At the same time, individuals wintering in the deltaic Caspian plains in Iran and in the Prikubanskaya Plain in southern Russia found areas with a rich and affordable food which caused minimal daily movements and a minimum radius of the daytime territory. Based on telemetry and visual observations, a previously unknown area of sustainable wintering of greater spotted eagles in the south of European Russia has been localized. The paddy rice fields in the Prikubanskaya Plain as the most important forage habitat and the probable significance of the numerous and available brown rat (Rattus norvegicus) as the main prey species in winter are discussed. The data obtained form an important basis for the development of a strategy for the protection of this rare vulnerable species across the entire distribution range.