Dracunculoid nematodes (Spirurida: Dracunculoidea) of fishes from the Volga River delta

Faunistic and some morphological data, as well as nomenclature notes on dracunculoid nematodes parasitising fishes in the Volga River delta, are presented. The author replaced a preoccupied generic name Molnaria Moravec, 1968 (Skrjabillanidae) by the new name Kalmanmolnaria nom. nov. The validity of Philometroides lusii (Vismanis, 1962) comb. nov. as a senior objective synonym of Philometroides lusiana (Vismanis, 1967) Ivaschkin et al., 1971 is restored.     

Range expansion of quagga mussels Dreissena rostriformis bugensis in the Volga River and Caspian Sea basin

In 1992, we discovered populations of the nonindigenous quagga mussel Dreissena rostriformis bugensis in the middle reaches of the Volga River. The same species was found in samples collected between 1994 and 1997 in the Volga delta and in shallow areas of the Northern Caspian Sea. D. r. bugensis always co-occurred with its more widespread congener, the zebra mussel D. polymorpha (Pallas 1771). The quagga mussel's contribution to total Dreissena abundance increased over time in the middle Volga reservoirs and Volga River delta. D. r. bugensis was common in the Volga portion of Rybinsk Reservoir during 1997 and, by 2000, it was in Uglich, Rybinsk and Gorky Reservoirs on the Upper Volga River. D. r. bugensis was neither found in Ivankov Reservoir, nor in terminal sections of the Volga-Baltic corridor including the eastern Gulf of Finland. Presently, all but the northern-most regions of the Volga River have been colonized by D. r. bugensis. We hypothesize that its introduction into the Volga River and Caspian basin occurred no later than the late 1980s via commercial shipping that utilized the Volga-Don waterway to navigate between the source Black-Azov Sea region and recipient areas on the Volga River. Larval drift likely contributed to establishment of populations at downstream sites, while human-mediated vectors may be responsible for introductions to upstream locations on the Volga River. We anticipate continued northward dispersal in conjunction with shipping activities.     

Range expansion of quagga mussels Dreissena rostriformis bugensis in the Volga River and Caspian Sea basin

In 1992, we discovered populations of the nonindigenous quagga mussel Dreissena rostriformis bugensis in the middle reaches of the Volga River. The same species was found in samples collected between 1994 and 1997 in the Volga delta and in shallow areas of the Northern Caspian Sea. D. r. bugensis always co-occurred with its more widespread congener, the zebra mussel D. polymorpha (Pallas 1771). The quagga mussel's contribution to total Dreissena abundance increased over time in the middle Volga reservoirs and Volga River delta. D. r. bugensis was common in the Volga portion of Rybinsk Reservoir during 1997 and, by 2000, it was in Uglich, Rybinsk and Gorky Reservoirs on the Upper Volga River. D. r. bugensis was neither found in Ivankov Reservoir, nor in terminal sections of the Volga-Baltic corridor including the eastern Gulf of Finland. Presently, all but the northern-most regions of the Volga River have been colonized by D. r. bugensis. We hypothesize that its introduction into the Volga River and Caspian basin occurred no later than the late 1980s via commercial shipping that utilized the Volga-Don waterway to navigate between the source Black-Azov Sea region and recipient areas on the Volga River. Larval drift likely contributed to establishment of populations at downstream sites, while human-mediated vectors may be responsible for introductions to upstream locations on the Volga River. We anticipate continued northward dispersal in conjunction with shipping activities.     

Growth,size-age structure of catches and reproduction of the Volga zander <Emphasis Type="Italic">Sander volgensis</Emphasis> (Percidae) in the upper part of the Volga stretch of the Kuibyshev Reservoir

Conditions of reproduction, size-age structure of catches, and the growth of the Volga zander Sunder volgensis in the upper part of the Volga stretch of the Kuibyshev Reservoir from 2002 to 2007, as well as its fishery in this water body, are considered. A decrease in catches of the proportion of large elder age groups of the Volga zander in the period of destabilization of the reservoir ecosystem, as compared to the phase of its relative stabilization from the 1970s to the 1980s, and a decrease in the commercial catch were established. Besides, retardation of its growth in connection with the deterioration of the ecological situation is observed, but the average level of reproduction is retained, which at the organization of rational fishery can lead to the restoration of the Volga zander stock.     

The taxonomic diversity of the parasites of fishes in the Volga basin. III. Aspidogastrea and Trematoda

A checklist of Aspidogastrea and Trematoda parasitizing fishes in the Volga basin is given. The checklist includes host species names for the each parasite and data on the occurrence of parasites in different parts of the Volga basin. The data on trematodes from 69 fish species are presented. The list containes 107 species and 1 subspecies names of trematodes, and 1 species of Aspidogastrea. The family Diplostomidae is represented by the most number of species (22). Six species of trematodes (Amurotrema dombrovskajae, Sanguinicola skrjabini, Nicolla skrjabini, Plagioporus skrjabini, Apophallus muehlingi, Rossikotrema donicum) have been introduced into Volga River along with aclimatizated fishes or penetrated into its basin by self-migration to new water bodies.     

The taxonomic diversity of the parasites of agnathans and fishes in the Volga basin. I. Parasitic protozoa (Protozoa)

A checklist of protozoa parasitizing fishes in the Volga basin is given. The checklist includes host species names for the each parasite and data on the occurrence of parasites in different parts of the Volga basin. The data on parasitic protozoa from 52 fish species are presented. The list containes 224 species and 10 subspecies names of the parasites. 9 species (Trypanosoma gracilis, Eimeria cheni, E. sinensis, Zschokkella striata, Chloromyxum cyprini, Myxobolus amurensis, M. driagini, M. pavlovskii, and Balantidium ctenopharyngodoni) were introduced into the Volga basin from the Amur basin along with acclimatizated fishes.     

Chromosomal polymorphism in the populations of malaria mosquito <Emphasis Type="Italic">Anopheles messeae</Emphasis> (Diptera,Culicidae) in the Volga region

We studied the species composition and chromosomal variability of malaria mosquitoes in the Volga Basin (Upper, Middle, and Lower Volga regions). We investigated larvae karyotypes of sibling species of the Anopheles maculipennis group. We calculated the frequencies of chromosomal inversions in the local populations of the dominant species An. messeae. We discovered that karyotypic structure of An. messeae populations depends on landscape-climatic zones. Populations of the Upper, Middle and Lower Volga differ in frequency of chromosome inversions XL, 2R, 3R, and 3L.     

International environmental implications of Soviet development of the Volga River

Hydrologic alteration of major rivers has the potential for environmental damage on an international scale. Soviet regulation of the Volga River is a case in point. Iran, bordering on the Caspian Sea to which the Volga is tributary, has been harmed by changes in the sea's physical and biological character which are partially attributable to Soviet modification of the Volga's natural flow regime. Soviet plans for southward diversion of flow from the European Arctic and Siberia, partially intended to alleviate the Caspian problem, could pose an even more serious international hazard. Possible adverse consequences range from further imperiling the survival of the Atlantic salmon to hemispheric, perhaps even global, climatic changes. The already apparent consequences of Volga development and possible future ramifications of related diversion measures emphasize the need for caution as well as international cooperation and consultation in planning the alteration of major river basins.     

Morphological and Genetic Traits of Pikeperch <Emphasis Type="Italic">Sander lucioperca</Emphasis> of the Volga–Akhtuba Aquatic System: on the Spatial Structure of a Species in the Lower Volga Basin

Characters of external morphology and ten loci of microsatellite DNA are investigated in pikeperch Sander lucioperca from the Volga–Akhtuba water system on sites of the Akhtuba and the Volga situated 150 km from the beginning of the Volga Delta and 300 km from the dam of the Volgograd Power Plant. Significant differences in plastic characters are found between samples from the Akhtuba and the Volga. Differences are also found in the genetic diversity of pikeperch: the found alleles are more numerous in most loci and the mean value of allele diversity is higher in the sample from the Akhtuba. At the same time, the calculated distance between samples of pikeperch is not certain. However, this may follow from limitations accompanying the calculation of differentiation parameters. The allele diversity and heterosis of pikeperch from the Akhtuba and the Volga are higher than those in populations from the Baltic basin and Western Europe. The known differences in external morphology and in genetic characters indicate to the present day partial separation of the Volga pikeperch from the Akhtuba pikeperch and that the found polymorphism of morphological and genetic characters reflects the ecological plasticity of the species, which is an adaptive response to changing environmental conditions.     

Taxonomic diversity of parasites from agnathans and fishes in the Volga basin. II. Parasitic Coelenterata and Monogenea

A checklist of the Monogeneans and Coelenterates parasitizing fishes in the Volga River basin is given. The list of hosts with the data on their occurrence in different areas of the Volga River basin is provided for each parasite species. The data on the parasites from 46 fish species are presented. The checklist includes 139 species and 6 taxa of subspecific rank. 9 species (Dactylogyrus aristichthys, D. ctenopharyngodonis, D. hypophthalmichthys, D. lamellatus, D. nobilis, D. suchengtaii, Pseudodactylogyrus bini, P. microrchis, and Eudiplozoon nipponicum) were introduced into the Volga River basin accidentally together with the Far Eastern fish species during the process of their naturalization.     

On the populational structure of sterlet <Emphasis Type="Italic">Acipenser ruthenus</Emphasis> (Acipenseridae) from the Volga Lower reaches

Trawl surveys made in the Lower Volga and the Caspian Sea revealed that the full life cycle of the Lower Volga sterlet is confined to fresh water and only single specimens living in the Volga-Caspian canal can live in the canal and swim to weakly saline and stagnant waters. Therefore, the sterlet living in the Volga-Caspian canal with its expressed current should be attributed to potamodromous forms. In consideration of the data on distribution, the variation of the complex of plastic characteristics, growth rate, and infestation with the parasite Amphilina foliacea it is concluded that within the Lower Volga population of sterlet three populations of the lower rank may be discerned: the Volgograd population living from the Volgograd Hydroelectric Complex dam to the Kamennyi Yar settlement; the eastern population living in the top of the Volga Delta and Buzan channel; and the western population in the Volga-Caspian canal. These populations differ in some plastic characteristics, linear growth rate, the part of fish infested with the parasite A. foliacea, and in the occurrence of anomalies in the structure of mature ovicells.     

Chlorophyll content and factors affecting its spatial distribution in the Middle Volga reservoirs

On the basis of the data obtained during field observations in the summer low water period of 2001, the patterns of chlorophyll distribution and its relation to hydrological and hydrochemical factors in two eutrophic reservoirs of the Middle Volga are studied. The hydrological structure of the Gorky Reservoir, where the Volga water mass dominates, is homogeneous, while in the Cheboksary Reservoir along with the eutrophic Volga waters, the mesotrophic Oka water masses can be distinguished keeping their abiotic and biotic features over a long distance. Phytoplankton in the two contiguous reservoirs with different flow regimens and anthropogenic loads responds differently to the external influence. An autotrophic community in the Gorky Reservoir is more stable and depends little on abiotic factors which account for ∼63% of the explained chlorophyll variation. In the Cheboksary Reservoir under maximal for the Volga cascade flow velocity and anthropogenic load, the development and distribution of phytoplankton are almost completely (R ² = 0.93) controlled by these factors. The trophic state of the reservoirs has not changed as compared to the beginning of the 1990s.     

Evidence of mitochondrial DNA clones of Siberian sturgeon, Acipenser baerii, within Russian sturgeon, Acipenser gueldenstaedtii, caught in the River Volga

Eleven of 34 sturgeons caught in the River Volga classified morphologically as Acipenser gueldenstaedtii were identified as Acipenser baerii from sequence analysis of the mitochondrial cytochrome- b gene. The Caspian Sea and its tributaries including the Volga are not native habitats of A. baerii . No A. baerii haplotype was observed in A. gueldenstaedtii from the Sea of Azov or the South Caspian Sea. Genetic contamination of A. gueldenstaedtii with A. baerii or A. baerii hybrids has occurred in the Volga. Crosses and backcrosses of these specimens with native A. gueldenstaedtii resulted in the loss of the morphological diagnostic A. baerii features. These findings are of special concern for conservation and management programmes, as well as for specimen identification for caviar trading control.     

Systematics of Mexiconema cichlasomae (Nematoda: Daniconematidae) based on sequences of SSU rDNA

The molecular characterization of the daniconematid dracunculoid Mexiconema cichlasomae Moravec, Vidal, and Salgado-Maldonado, 1992 through the sequencing of SSU rDNA from adult individuals is presented herein. Additionally, preliminary genetic relationships of this nematode are inferred from alignment of sequences generated previously for other dracunculoids. Maximum parsimony and maximum likelihood analyses recovered identical trees. As anticipated by previous taxonomic work, M. cichlasomae is putatively closely related to skrjabillanid dracunculoids represented by Molnaria intestinalis (Dogiel and Bychovsky, 1934) and Skrjabillanus scardinii Molnár, 1966 SSU rDNA sequences, but the relationships of this newly discovered clade to other dracunculoid clades remain unresolved.     

On the distribution of riffle minnow <Emphasis Type="Italic">Alburnoides bipunctatus</Emphasis> (Cyprinidae) in the Volga Basin

On the basis of analysis of our own and published data on the distribution of the riffle minnow Alburnoides bipunctatus rossicus in rivers of the Volga Basin, the eastern boundary of the range of this subspecies included in the Red Data Book of the Russian Federation is specified. It is shown that A. bipunctatus is widely distributed in the entire basin of the Middle Volga and Kama, except the extreme northeast (mountain tributaries of the Upper Kama upstream the Chusovaya River), and rarely occurs in the Upper Volga Basin. The Tereshka River (Ulyanov oblast) and Chapaevka (Saratov oblast) should be considered the southern boundary of the distribution of the subspecies in the Volga Basin. Since the mid-1990s, a drastic and uniform increase in the number of findings and the abundance of A. bipunctatus is recorded. This species has become a common fish in many rivers and, in some cases, a dominant species in river ichthyocenoses. Possible causes of these changes are discussed, and a conclusion is made concerning the need of the revision of the status of the subspecies A. bipunctatus rossicus.     

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.     

Population Characteristic of the Volga zander <Emphasis Type="Italic">Sander volgense</Emphasis> (Percidae) in the Kuibyshev reservoir

The analysis of the size composition, age structure, linear growth, and fecundity of the Volga zander Sander volgense has been performed in the Kuibyshev reservoir. To date, the growth rates of the species have decreased slightly compared to the 1970s. Over the period from 2000 to 2013, catch volumes of Volga zander tended to increase.     

Factors influencing the natural reproduction decline in the beluga (Huso huso,Linnaeus, 1758), Russian sturgeon (Acipenser gueldenstaedtii,Brandt & Ratzeburg, 1833), and stellate sturgeon (A. stellatus,Pallas, 1771) of the Volga–Caspian basin: A review

The review describes the changes in natural reproduction of three important sturgeon species in the Volga–Caspian basin: (a) the beluga (Huso huso Linneaus, 1758), (b) the Russian sturgeon (Acipenser gueldenstaedtii Brandt &Ratzeburg, 1833), and (c) the stellate sturgeon (Acipenser stellatus Pallas, 1771). Since the past 60 years, these species responded to severe influences of natural and anthropogenic factors. On the basis of original and published data, an analysis has been made of (a) the numbers of larvae migrating from spawning sites (according to plankton net survey), (b) fecundity and histological anomalies in gonad development, (c) the numbers of adult sturgeons in the Caspian Sea and of spawners migrating to the Volga River (according to trawl and beach seine survey), and (d) foraging resources for the sturgeons. The results show that their natural reproduction in the Volga–Caspian basin has declined drastically during the past decades under the impact of (a) fluctuations of the Caspian Sea level and flow discharge from the Volga River, (b) blockage of sturgeon migration routes and loss of spawning sites because of dam construction, (c) water pollution in the lower reaches of the Volga River and in the Caspian Sea, and (d) intensive and selective illegal and unreported fishing. The relative significance of these factors has been changing during the study period.     

Reproductive parameters of roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.) from the Rybinsk Reservoir reaches differing in anthropogenic loads

The results of a study on the parameters of reproductive capacity in roach from the Sheksna and the Volga reaches of the Rybinsk Reservoir are presented. The Volga reach is relatively clean, while the Sheksna reach is subject to the strongest anthropogenic load. In 2011, the average values of the absolute and relative fecundity, as well as the egg size, in roach Rutilus rutilus (L.) from the Volga reach were higher than those in roach from the Sheksna reach, but differences are mainly statistically insignificant. The data of the study indicate the adaptation of the investigated roach to the negative influence of the Sheksna reach contamination and, in particular, its preservation of a sufficient level of reproductive capacity.