Zoogeographic analysis of the fauna of the family Asilidae (Diptera) of the Lower Volga area

Based on the author’s own and the literature data, the zoogeographic analysis of robber flies (Asilidae) of the Lower Volga area was carried out for the first time. A total of 21 range types were distinguished and the fractions of different chorological groups in the fauna were determined. The zoogeographic structure of faunal complexes of robber flies inhabiting biotopes with different plant associations was studied.     

Lepidopteran pests in the Upper Volga area (Lepidoptera)

Data on 154 species of lepidopteran pests in the Upper Volga region, of which 9 are considered as principal, 29 as minor, and 116 as potential pests are summarized. Most of harmful species belong to the families Tortricidae (27), Noctuidae (24), Gelechiidae (11), Gracillariidae (9), Geometridae (8), and Lymantriidae (6). The pests of forest trees and shrubs are most numerous, followed by the pests of fruit trees and berry shrubs, pests of ornamental trees and shrubs, etc. There is no lepidopteran pest of field and forage crops in the region. On the whole, the economic importance of Lepidoptera in the Upper Volga region is lower than that of the other insect orders.     

Comparative analysis of the structure and fauna of endosymbionts of communities of two dreissenid species (Mollusca,Dreissenidae) in the Upper Volga reservoirs

Investigations into the structure of communities of two dreissenid species are presented (native Dreissena polymorpha Pallas, 1771, and invasive D. bugensis Andrusov, 1897) in the Gorky and Rybinsk reservoirs (the Upper Volga basin). Significant interspecific and interpopulational differences in the main quantitative parameters and the fauna of endosymbionts are revealed between these mollusks.     

Vertical Distribution of Chlorophyll in the Upper Volga Reservoirs

The vertical distribution of phytoplankton (chlorophyll a, CHL) was investigated in August 2015 at 25 sampling stations in the Ivankovo, Uglich, and Rybinsk reservoirs (Upper Volga, Russia) using a bbe Moldaenke Fluoroprob submersible fluorimeter. Three types of CHL vertical distribution were identified under homothermy. There was a gradual CHL decline in the water column at the upper part of reservoirs; a sharp decline at a certain depth in most riverine sections; and uniform distribution opposite the mouth of a small river (the Kashinka River, Uglich Reservoir), as well as at the open lacustrine sites of the Rybinsk Reservoir under wind-driven mixing. The average CHL content in the euphotic layer at the stations of three groups were 25.0 ± 6.3, 44.1 ± 4.0, and 20.8 ± 2.9 μg/L, respectively; the CHL contributions to the PAR absorption were 47 ± 9%, 66 ± 4%, and 38 ± 6%. Under thermal stratification the vertical distribution of CHL corresponds to the course of the temperature dynamics (r = 0.85).     

Early Valdai carpological assemblages from the Upper Volga Region

Results of modern carpological studies of the Ples section in the Upper Volga Region are discussed. The section includes sediments of the Mikulino (Eemian) Interglacial and Early Valdai (Early Weichselian) Glacial. Particular attention is given to Early Valdai carpological assemblages. The analysis of their composition and comparison with palynological data from the locality and carpological data from western regions of the East European Plain allows one to assign the assemblages under study to two relatively warm episodes of interstade type. For the first time, the carpological characteristics of two warm episodes are given for this territory.     

Contribution to the stone-fly (Plecoptera) fauna of the Volga and Don river basins

In the Volga and Don river basins, 17 stonefly species are known: 16 from the Volga, and 6 from the Don basin. The fauna is dominated by the species with wide, European (Isogenus nubecula, Nemoura flexuosa, N. dubitans, Amphinemura sulcicollis, Brachyptera braueri, Isoperla difformis, I. grammatica, Leuctra hippopus, Xanthoperla apicalis, Siphonoperla burmeisteri) and Transpalaearctic ranges (Taeniorterykh nebulosa, Nemurella pictetii, Amphinemura borealis, Nemoura cinerea, Capnia atra, Leuctra fusca, Isoperla obscura).     

Taxonomic and functional homogenization of an endemic desert fish fauna

Aim The highly endemic fishes of the arid Southwest USA have been heavily impacted by human activities resulting in one of the most threatened fish faunas in the world. The aim of this study was to examine the patterns and drivers of taxonomic and functional beta diversity of freshwater fish in the Lower Colorado River Basin across the 20th century. Location Lower Colorado River Basin (LCRB). Methods The taxonomic and functional similarities of watersheds were quantified to identify patterns of biotic homogenization or differentiation over the period 1900–1999. Path analysis was used to identify the relative influence of dam density, urban land use, precipitation regimes and non‐native species richness on observed changes in fish faunal composition. Results The fish fauna of the LCRB has become increasingly homogenized, both taxonomically (1.1% based on β_sim index) and functionally (6.2% based on Bray–Curtis index), over the 20th century. The rate of homogenization varied substantially; range declines of native species initially caused taxonomic differentiation (?7.9% in the 1960s), followed by marginal homogenization (observed in the 1990s) in response to an influx of non‐native species introductions. By contrast, functional homogenization of the basin was evident considerably earlier (in the 1950s) because of the widespread introduction of non‐native species sharing similar suites of biological traits. Path analysis revealed that both taxonomic and functional homogenization were positively related to the direct and indirect (facilitation by dams and urbanization) effects of non‐native species richness. Main conclusions Our study simultaneously examines rates of change in multiple dimensions of the homogenization process. For the endemic fish fauna of the LCRB, we found that the processes of taxonomic and functional homogenization are highly dynamic over time, varying both in terms of the magnitude and rate of change over the 20th century.     

Fish fauna and fisheries of large European rivers: examples from the Volga and the Danube

The role of herbivores in regulating aquatic plant dynamics has received growing recognition from researchers and managers. However, the evidence for herbivore impacts on aquatic plants is largely based on short-term exclosure studies conducted within a single plant growing season. Thus, it is unclear how long herbivore impacts on aquatic plant abundance can persist for. We addressed this knowledge gap by testing whether mute swan (Cygnus olor) grazing on lowland river macrophytes could be detected in the following growing season. Furthermore, we investigated the role of seasonal changes in water current speed in limiting the temporal extent of grazing. We found no relationship between swan biomass density in 1 year and aquatic plant cover or biomass in the following spring. No such carry-over effects were detected despite observing high swan biomass densities in the previous year from which we inferred grazing impacts on macrophytes. Seasonal increases in water velocity were associated with reduced grazing pressure as swans abandoned river habitat. Furthermore, our study highlights the role of seasonal changes in water velocity in determining the length of the mute swan grazing season in shallow lowland rivers and thus in limiting the temporal extent of herbivore impacts on aquatic plant abundance.     

Dreissenid species (Mollusca,Dreissenidae) in the Upper Volga reservoirs

The results of our long-term studies of populations of two dreissenid species (Dreisena polymorpha Pallas, 1771 and D. bugensis Andrusov, 1897) in Rybinsk and Gorkii reservoirs have been analyzed. New habitats of D. bugensis have been found in Rybinsk Reservoir.     

A confined taste area in a lepidopteran brain

Knowledge about the neuronal pathways of the taste system is interesting both for studying taste coding and appetitive learning of odours. We here present the morphology of the sensilla styloconica on the proboscis of the moth Heliothis virescens and the projections of the associated receptor neurones in the central nervous system. The morphology of the sensilla was studied by light microscopy and by scanning- and transmission electron microscopy. Each sensillum contains three or four sensory neurones; one mechanosensory and two or three chemosensory. The receptor neurones were stained with neurobiotin tracer combined with avidin-fluorescein conjugate, and the projections were viewed in a confocal laser-scanning microscope. The stained axons entered the suboesophageal ganglion via the maxillary nerves and were divided into two categories based on their projection pattern. Category one projected exclusively ipsilaterally in the dorsal suboesophageal ganglion/tritocerebrum and category two projected bilaterally and more ventrally in the suboesophageal ganglion confined to the anterior surface of the neuropil. The bilateral projecting neurones had one additional branch terminating ipsilaterally in the dorsal suboesophageal ganglion/tritocerebrum. A possible segregation of the two categories of projections as taste and mechanosensory is discussed.     

Taxonomic and trophic structures of dominants in the zooperiphyton of waterbodies and watercourses of the upper Volga basin

All the main trophic groups of invertebrates are presented in the compositions of dominant assemblages of zooperiphyton in the studied waterbodies and watercourses. The strong pollution of water by suspended solids of anthropogenic origin in the water of the upper Volga reservoirs leads to the suppression of typically sessile filter-feeding invertebrates (sponges, bryozoans, and Dreissena) able to form the highest biomass of zooperiphyton using natural food items. The conditions of the disturbed structure of food resources are favorable for the development of detritivores-gatherers. In small rivers receiving industrial wastewaters, excessive amounts of food in the water column and in the form of sediments on the substrates suppresses invertebrates-biofowlers and facilitates the expansion of the benthic larvae of chironomids of g. Chironomus (combining the filtration and gathering of food particles on the substrates) to the vacant spatial niches. At the same time, the role of nematodes and oligochaetes with prevailing detritophages increases. In the acidified lakes of the Darwinsky National Reserve, the decrease in the total species diversity of zooperiphyton is accompanied by decreases in the role of filter-feeding invertebrates. The chironomid larvae and oligochaetes prevailed in the poor zoocenoses. The roles of predatory caddisfly larvae, black gnats, and nematodes increased. The labile structural characteristics of zooperiphyton with the conservation of the historically formed methods of foraging are the main modern way that biofouling communities adapt to changes in the quality and quantity of food resources upon modern anthropogenic pollution of the aquatic environment.     

Parasitic fauna of the muskrat from the Upper Ob' pine forest

The gamasid mites Laelaps multispinosus and Hirstionyssus isabellinus, flea Ceratophyllus (Megabotris) rectangulatus, trematodes Plagiorchis proximus, P. eutamiatis, P. obensis, P. multiglandularis, Quinqueserialis quinqueserialis and Opisthorchis felineus, cestodes Aprostotandria macrocephala and Alveococcus multilocularis, larvae, were found in 78 specimens of Ondatra zibethica from water bodies of the Upper Ob pine forest. The mite L. multispinosus is reported as the most abundant ectoparasite of this population of the muskrat. As to helminths most abundant and frequently encountered are Q. Quinqueserialis and A. macrocephala which at high infection intensity can cause decrease in the muskrat abundance.     

Taxonomic composition and zoogeographic characteristics of the flea fauna (Siphonaptera) of Russia

255 species and 59 subspecies of fleas from 55 genera of 7 families are known from Russia, which is 30% of the Palaearctic fauna. Additionally, over 187 species of 47 genera from 7 families are known from the neighboring territories of Central and Southern Europe, Transcaucasia, Kazakhstan, Middle Asia, Mongolia, Northeast China, and Japan. 13 species of 12 genera are known only from Russia. Noteworthy is the low percent of endemic species (not more than 4%) and genera (one genus) in the Russian fauna. The principal centers of taxonomic diversity in the Palaearctic, including many endemic species and genera, lie in the Eastern Asian, Central Asian, and Turano-Iranian Subregions, outside Russia and the Euro-Siberian Subregion. The bulk of the Russian fauna is formed by the species and genera of the three largest flea families: Hystrichopsyllidae, Ceratophyllidae, and Leptopsyllidae. The family Ceratophyllidae has the greatest number of genera in the Russian fauna, and Hystrichopsyllidae, the greatest number of species. Western (Western and Western-Central Palaearctic; 84 species from 41 genera of 7 families) and Eastern (Central-Eastern and Eastern Palaearctic; 78 species from 42 genera of 6 families) species are nearly equally represented in the Russian fauna.     

Taxonomic diversity of parasites in agnathans and fishes from the Volga River basin v. Nematoda and Gordiacea

The checklist of Nematoda and Gordiacea parasitizing agnathans and fishes in the Volga River basin is presented. Hosts and areas of distribution are indicated for each parasite species. The checklist includes 39 species and 11 nonidentified larval forms of nematodes from 51 fish species. Larvae of Gordius sp. are found in 5 fish species. The nemadote species Sinoichthyonema amuri have been introduced into the Volga basin occasionally during the process on introduction of fish species from Amur River.     

Ecology of diapausing copepodids of Cyclops kolensis Lill. in reservoirs of the Upper Volga

Cyclops kolensis Lill. forms dense populations in different water-bodies of the Upper Volga basin. In spring, when the other planktonic crustaceans have not yet appeared, C. kolensis is an important food object for fishes. Its active reproduction occurs from April to the beginning of June. A rapid accumulation of stage IV copepodids in the plankton occurs in June and at 12–14° they sink into the pelogene in a diapause stage. During the summer stagnation period the diapausing copepodids are distributed evenly over the bottom; their abundance here is 0.7–0.8 million ind. m^-2 (Rybinsk reservoir). During storms and autumn active water mixing the copepodids together with detritus are disturbed and brought to the deepest, silt rich, part of the water-bodies. After the ice formation and at the beginning of bottom heating the diapausing copepodids are transported by near bottom currents and are concentrated in depressions; their biomass here reaches 60 g m^-3. After the thermo-oxy-cline formation they revive and begin to live actively. Copepodids feed, accumulate adipose matter and in February–March they begin to moult.     

Overgrowing of protected shallow waters in the Upper Volga reservoirs in relation to their morphometry

The features of overgrowing of different types of protected shallow waters in the Ivankovo, Uglich, and Gorky reservoirs have been considered. The average degree of overgrowing increases in the following series: pocket-type shallow waters (37.3% of area), shallow waters behind islands (40.6), and bays (56.9). Helophytes contribute to the overgrowing of more than 50% of all types of protected shallow waters. The composition of plant community dominants of protected shallow waters of different types is very similar, because the reservoirs belong to the same cascade, are located in one climatic zone, and have similar ecotopes. The effect of morphometric parameters (area, volume, length, average width and depth) and their ratios (oblongness of water area, openness, and isolation) on the overgrowing of protected shallow water areas is expressed only at average values of these parameters and has an exponential form. The contribution of the area isolation to overgrowing is most significant (up to 55%).     

Content of total free nucleotides in the plankton of the Rybinsk reservoir (Upper Volga)

The content of total free nucleotides (TFNs) in the plankton of the Rybinsk reservoir and in specific size fractions of the plankton has been determined by the spectrophotometric method modified by the authors. The content of TFNs amounts to 58.1 ± 5.4, 75.2 ± 4.6, and 64.1 ± 7.3 μg/L in spring, summer, and autumn, respectively, and exhibits a close correlation with the total plankton biomass (r = 0.67), whereas the TFN/Chl parameter is closely correlated to the ratio of autotroph and heterotroph organism biomass (r = 0.96). The contribution of the fraction of more than 3 μm in size (microplankton and nanoplankton) to the TFN pool is 77 ± 4% in spring, 74 ± 3% in summer, and 47 ± 3% in autumn, whereas the contribution of the fraction of 0.45–3 μm in size (ultraplankton) during these seasons is 23 ± 4, 26 ± 3, and 53 ± 3%, respectively. Regression equations that can be used to infer an estimate of plankton biomass from TFN content have been proposed.