Search

Metacercariae of Diplostomum petromyzifluviatilis (Digenea, Diplostomidae) from the brain of European river lamprey Lampetra fluviatilis from the Baltic Sea basin and Arctic lamprey Lethenteron camtschaticum from the White Sea basin were studied with the use of genetic and morphological methods. Phylogenetic analysis based on cox1 marker showed that the parasites of both lamprey species were conspecific with Diplostomum sp. Lineage 4 of Blasco-Costa et al. (2014). The name Diplostomum petromyzifluviatilis Müller (Diesing, 1850) has historical precedence as a species described from the brain of lampreys and should be used in genus nomenclature. There were no morphological qualitative differences between the metacercariae from the two lamprey species but those from L. fluviatilis were larger than those from L. camtschaticum. We expanded the data on the second intermediate hosts and the localization of D. petromyzifluviatilis, showing that its metacercariae occur not only in the brain of lampreys but also in the brain and the retina of three-spined stickleback Gasterosteus aculeatus and the vitreous humour of the perch Perca fluviatilis across the European part of the Palearctic., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The family Glossiphoniidae is a diverse and widespread clade of freshwater leeches, playing a significant role in functioning of aquatic ecosystems. The taxonomy and biogeography of leeches from temperate, subtropical, and tropical regions attracted much attention of zoologists, while their taxonomic richness and distribution in the Arctic are poorly understood. Here, we present an overview of the Eurasian Arctic Glossiphoniidae based on the most comprehensive occurrence and DNA sequence datasets sampled to date. This fauna contains 14 species, belonging to five genera and three subfamilies. One genus and five species are new to science and described here. The world's northernmost occurrences of glossiphoniids are situated on the Taymyr Peninsula at 72° N, although further records at higher latitudes are expected. Most Arctic leeches are characterized by broad ranges crossing several climatic zones (e.g., Glossiphonia balcanica and G. nebulosa), although the distribution of two new species may be confined to the high-latitude areas. The Taymyr Peninsula with the nearby Putorana Plateau represents the most species-rich area (totally 9 species), while the European Arctic, Iceland, Kolyma Highland, and Chukotka Peninsula house depleted faunas (2-4 species per subregion). Finally, we show that the high-latitude melanism is a common phenomenon in glossiphoniid leeches., (© 2022. The Author(s).)

Fatty acids (FA) of muscle tissue of Salvelinus species and its forms, S. alpinus , S. boganidae , S. drjagini , and S. fontinalis , from six Russian lakes and two aquacultures, were analyzed. Considerable variations in FA compositions and contents were found, including contents of eicosapentaenoic and docosahexaenoic acids (EPA and DHA), which are important indicators of fish nutritive value for humans. As found, contents of EPA+DHA (mg·g -1 wet weight) in muscle tissue of Salvelinus species and forms varied more than tenfold. These differences were supposed to be primarily determined by phylogenetic factors, rather than ecological factors, including food. Two species, S. boganidae and S. drjagini , had the highest EPA+DHA contents in their biomass and thereby could be recommended as promising species for aquaculture to obtain production with especially high nutritive value. Basing on revealed differences in FA composition of wild and farmed fish, levels of 15-17-BFA (branched fatty acids), 18:2NMI (non-methylene interrupted), 20:2NMI, 20:4n-3, and 22:4n-3 fatty acids were recommended for verifying trade label information of fish products on shelves, as the biomarkers to differentiate wild and farmed charr.

Genetic diversity and colonization routes of noble salmons were studied using a partial nucleotide sequence of the mitochondrial COI gene. The brown trout S. trutta, which is the most ancient species of the genus, was concluded to originate from the modern southeastern Pontic-Caspian area, which is currently inhabited by members of the subspecies S. trutta oxianus. Migrating westward while the Paratethys was in existence (5-34 million years ago), species of the genus colonized ancient water bodies in the modern Mediterranean basin and formed many isolated populations that survived desiccation of the Mediterranean Sea (5-6 million years ago). The Strait of Gibraltar mediated brown trout migrations to Northern Europe; the subspecies S. trutta trutta belongs to a relatively young phylogenetic lineage of the species. A separate brown trout lineage, currently classified as the subspecies S. trutta labrax, formed most likely in the area of the modern Danube basin, which was a relatively separate part of the Paratethys and was sometimes isolated as the Pannonian Lake. A highly divergent phylogenetic lineage of Atlantic salmon (S. salar) haplotypes originates from a haplotype of the brown trout that inhabited the area of the modern Strait of Gibraltar.

A hypothesis was advanced and grounded that the total content of eicosapentaenoic (EPA, 20:5n-3) and docosahexaenoic (DHA, 22:6n-3) acids in fish muscle tissue is associated with the species-specific (taxon-specific) duration of embryo development. A meta-analysis of the original and published data was performed using fishes of the families Coregonidae and Salmonidae as an example. Fishes with longer embryo development times, which are observed at lower temperatures, were found to have significantly higher EPA + DHA contents in muscles as compared with the species that belong to the same families but have shorter embryo development times. This association was explained by the fact that an embryo forms more cells per unit tissue volume at lower temperatures, which requires a greater specific amount of cell membranes and, therefore, greater amounts of EPA and DHA to produce them.

Freshwater mussels are ecosystem engineers and keystone species in aquatic environments. Unfortunately, due to dramatic declines this fauna is among the most threatened globally. Here, we clarify the taxonomy and biogeography of Russian Unionidae species based on the most comprehensive multi-locus dataset sampled to date. We revise the distribution and assess the conservation status for each species. This fauna comprises 16 native species from 11 genera and 4 tribes: Anodonta, Pseudanodonta (Anodontini); Amuranodonta, Beringiana, Buldowskia, Cristaria, Sinanodonta (Cristariini); Middendorffinaia, Nodularia, Unio (Unionini); and Lanceolaria (Lanceolariini). No country-level endemic species are known in Russia, except for Buldowskia suifunica that may also occur in China. Sinanodonta woodiana, a non-native species, was introduced from China. Russia comprises the northern parts of Western and Eastern Palearctic subregions. The first subregion with six species encompasses a huge area from the western boundary of Russia to the Lena Basin in Siberia. The second subregion with 10 species covers the Amur Basin, rivers east of the Lena Basin, coastal basins of the Japan Sea, and the North Pacific Islands. The fauna of Russia primarily includes widespread generalist species that are here considered Least Concern (LC). However, Buldowskia suifunica and Sinanodonta lauta have restricted distributions and are assessed here as Vulnerable (VU) and Endangered (EN), respectively.

Freshwater mussels (Unionida) are one of the most imperiled animal groups worldwide, revealing the fastest rates of extinction. Habitat degradation, river pollution and climate change are the primary causes of global decline. However, biological threats for freshwater mussels are still poorly known. Here, we describe a diverse ecological group of leeches (Hirudinea: Glossiphoniidae) inhabiting the mantle cavity of freshwater mussels. So far, examples of mussel-associated leech species are recorded from East Asia, Southeast Asia, India and Nepal, Africa, and North America. This group comprises a dozen glossiphoniid species with a hidden life style inside the mantle cavity of their hosts largely overlooked by researchers. We show that the association with freshwater mussels evolved independently in three leech clades, i.e. Batracobdelloides, Hemiclepsis, and Placobdella, at least since the Miocene. Seven mussel-associated leech species and two additional free-living taxa are described here as new to science.

Margaritiferidae is a small freshwater bivalve family with 16 species. In spite of a small number of taxa and long-term history of research, several gaps in our knowledge on the freshwater pearl mussels still exist. Here we present the discovery of host fishes for Margaritifera dahurica, i.e. Lower Amur grayling, sharp-snouted lenok, and blunt-snouted lenok. The host fishes were studied in rivers of the Ussuri Basin. The identification of glochidia and fish hosts was confirmed by DNA analysis. The life cycle of M. dahurica and its glochidia are described for the first time. The SEM study of glochidia revealed that the rounded, unhooked Margaritifera dahurica larvae are similar to those of the other Margaritiferidae. Margaritifera dahurica is a tachytictic breeder, the larvae of which attach to fish gills during the Late August - September and finish the metamorphosis in June. Ancestral host reconstruction and a review of the salmonid - pearl mussel coevolution suggest that the ancestral host of the Margaritiferidae was a non-salmonid fish, while that of the genus Margaritifera most likely was an early salmonid species or their stem lineage. The overfishing of lenoks and graylings appears to be the most significant threat for this rare mussel species.

Samples from 11 populations of the Arctic char of the North-European part of Russia belonging to the anadromous and resident forms and two samples from Lake Sobach'e (Taimyr) were studied. The nucleotide sequence of the mitochondrial COI gene was determined in 60 individuals. In the majority of populations, the same COI haplotype was found. In some populations of the resident chars, haplotypes differing from the widespread haplotype in a single nucleotide substitution were found. The obtained genetic data give no reason to distinguish the resident form of the Arctic char from lakes of Karelia and the Kola Peninsula as an independent species, Salvelinus lepechini. The adaptation of the Arctic char to the unstable environmental conditions is ensured primarily by its phenotypic plasticity.

The effects of climate change on oligotrophic rivers and their communities are almost unknown, albeit these ecosystems are the primary habitat of the critically endangered freshwater pearl mussel and its host fishes, salmonids. The distribution and abundance of pearl mussels have drastically decreased throughout Europe over the last century, particularly within the southern part of the range, but causes of this wide-scale extinction process are unclear. Here we estimate the effects of climate change on pearl mussels based on historical and recent samples from 50 rivers and 6 countries across Europe. We found that the shell convexity may be considered an indicator of the thermal effects on pearl mussel populations under warming climate because it reflects shifts in summer temperatures and is significantly different in viable and declining populations. Spatial and temporal modeling of the relationship between shell convexity and population status show that global climate change could have accelerated the population decline of pearl mussels over the last 100 years through rapidly decreasing suitable distribution areas. Simulation predicts future warming-induced range reduction, particularly in southern regions. These results highlight the importance of large-scale studies of keystone species, which can underscore the hidden effects of climate warming on freshwater ecosystems.

This article is devoted to presenting the hypothesis explaining the fact of a considerable prevalence of phenotypic males among the triploid pink salmon as well as the regular occurrence of intersexes, which were revealed by us. This hypothesis also explains the large proportion (in some cases) in pink salmon populations of the individuals whose genetic sex does not match the phenotypic sex. We assume that the genes encoding the factors that contribute to the transformation of individuals into males (but not the marker sequences of the Y chromosome) are present not only in the Y chromosome of pink salmon but also in the X chromosome, although in smaller quantities.

In several Russian northern lakes and rivers, Arctic cisco Coregonus autumnalis, least cisco C. sardinella, peled C. peled, tugun C. tugun, broad whitefish C. nasus, whitefish C. lavaretus and vendace C. albula were sampled in periods of officially permitted commercial fishery. Special attention was paid to contents (mg g -1 of wet weight) of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in muscle tissues (filets), which are essential for human nutrition. The highest values of EPA + DHA content in semi-anadromous fish and freshwater fish were recorded for C. autumnalis from the Yenisei River, 17.60 mg g -1 wet weight, and for C. lavaretus from the Sobachye Lake, 16.61 mg g -1 wet weight, respectively. Intra-genus variations of EPA + DHA contents of Coregonus species were from 1.87 to 17.60 mg g -1 wet weight. Since the congeneric species were genetically close to each other, the variations in EPA and DHA contents were thought to be caused primarily by ecological factors: migrational capability, type of feeding and trophic status of aquatic ecosystems. In general, the majority of studied species appeared to be of a high nutritive value for humans, although unfavorable environmental conditions could considerably diminish this value.

The problem of how a gradual development of ecological and morphological adaptations combines with large genome rearrangements, which have been found to occur in the phylogeny of many groups of organisms, is a matter of discussion in the literature. The objective of this work was to study the problem with the example of salmonids, whose evolution included at least six events of multiple chromosome fusions. Large karyotype rearrangements are associated with a decrease in ecological and morphological diversity in salmonids. In the above example, genome rearrangements seem to distort the function of the genetic systems that are responsible for the occurrence of certain ecological forms in salmonids., Competing Interests: The authors declare no conflict of interest.

Triploid fish has become an important item of commercial aquaculture, but data on its fatty acid (FA) composition are still controversial, especially regarding essential polyunsaturated fatty acids, eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA). We studied FA composition and content of diploid and triploid pink salmon Oncorhynchus gorbuscha, reared in aquaculture in a bay of the White Sea (Russia). FA composition, measured as percentages of total FA of triploids and immature diploid females significantly differed from that of mature diploid fish. Specifically, mature diploids had higher percentage of EPA and DHA in their muscle tissue (filets) compared to that of triploids and immature diploid females. Nevertheless, the contents of EPA and DHA per mass of the filets in diploid and triploid specimens were similar. Thus, no special efforts are needed to improve EPA and DHA contents in filets of triploids., (Copyright © 2016 Elsevier Ltd. All rights reserved.)