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To date, a rather large set of both mathematical theories for species delimitation, based on single-locus genetic data, and their implementations as software products, has been accumulated. Comparison of the efficiencies of different delineation methods in the task of accumulating and analyzing data with reference to different taxa in different regions, is vital. The aim of this study was to compare the efficiency of fifteen single-locus species delimitation methods using the example of a fish species found in a single lake in European Russia (Lake Plescheyevo) with reference to other sequences of revealed taxa deposited in international databases. We analyzed 186 original COI sequences belonging to 24 haplotypes, and 101 other sequences previously deposited in GenBank and BOLD. Comparison of all 15 alternative taxonomies demonstrated that all methods adequately separate only the genera, while the number of delimited mOTUs differed from 16 (locMin) to 43 (HwM/CoMa). We can assume that the effectiveness of each method is correlated with the number of matches based on Ctax and MatchRatio criteria. The most comparable results were provided by bGMYC, mPTP, STACEY, KoT and ASAP and the most synchronous results were obtained from bGMYC, mPTP, STACEY and ASAP. We believe that these results are maximally realistic in the number of revealed mOTUs. A high genetic diversity, resulting in the existence of several mOTUs and phylogenetic lineages within many species, demonstrates the usefulness of the “polymorphic species” concept, which does not underestimate species richness and does not prevent the rational use and protection of biodiversity.

The stone moroko (or topmouth gudgeon), Pseudorasbora parva, is one of the most successful invasive species in the fresh waters of Europe and some regions of Asia. We analyzed the diversity of the mitochondrial COI gene in the genus Pseudorasbora and, in particular, in populations of P. parva from its native range (the Far East) and areas of recent dispersal. Four phylogenetic lineages of stone moroko were identified within its native range, and three of them contributed to the dispersal within more western regions of Eurasia. One of these lineages was initially distributed in the north of China and the Far East of Russia, the second one was in southern China, the third one was in the Korean Peninsula and, probably, in the adjacent regions of China. Geographical distribution of COI lineages suggests three donor regions of stone moroko invasions into more western regions of Eurasia: the basin of the Yangtze River, the northern (Russian) part of the Amur River basin, and the Sungari River basin (right tributary of the Amur in the territory of China).

Variability of the first invasive population of C. fluminea (O.F. Muller, 1774) from the Volga basin is studied using the mitochondrial cytochrome c oxidase subunit I gene fragment (COI mtDNA), and morphological features of the shells are characterized. A comparison with C. fluminalis (O.F. Muller, 1774) from the Kura River basin is made in order to avoid errors in species identification. All analyzed individuals belong to the most widespread R morphological type. The only nucleotide sequence haplotype we found is identical to the widespread variant prevailing in the populations of Corbicula with R morphological type in Europe and also in America. There were mollusks of different shell size groups in the sample. Corbicula larvae were detected in qualitative zooplankton samples and in the gills of adults. Therefore, the studied population reproduces independently and may possibly become a source for further species expansion.

The eastern Palaearctic is a centre of diversity for freshwater cladocerans (Crustacea), but little is known about the evolution and taxonomy of this diversity. Daphnia curvirostris is a Holarctic species complex that has most of its diversity in the eastern Palaearctic. We examined the phylogeography, rates of evolution and taxonomic status for each clade of the D. curvirostris complex using morphological and genetic evidence from four genes. The cybertaxonomical and morphological evidence supported an eastern Palaearctic clade, with at least four species (described here as the Daphnia korovchinskyi sp. nov. group) having diagnostic morphological characters. We also detected convergent morphological characters in the D. curvirostris complex that provided information about species boundaries. Two of the new species (Daphnia koreana sp. nov. and Daphnia ishidai sp. nov.) are known from single ponds and are threatened by human activity. Divergence time estimates suggested an ancient origin (12–28 Mya) for the D. korovchinskyi group, but these estimates are complicated by the small number of calibration points.

Biotic introductions are an ongoing disruption for many ecosystems. For passively dispersed freshwater zooplankton, transcontinental introductions have been common but are poorly studied in the southern hemisphere. Here we assess the hypothesis of recent introduction for populations of the Chydorus sphaericus group (Crustacea: Cladocera) in Australia. We analyzed 254 sequences (63 original sequences) from the cytochrome oxidase I region of mitochondrial DNA of Chydorus sp., which included global representation. Three Australian populations were connected with separate clades in the northern hemisphere, suggesting multiple colonization events for Australia. The timescale of the divergences was consistent with recent (Quaternary) dispersal. As Australian populations are exposed to migrating birds from the northern hemisphere, both avian and anthropogenic sources are candidates for dispersal vectors. We concluded that recent cross-hemisphere dispersal in the Chydorus sphaericus group is more common than previously believed.

Adequate species’ identification is critical for the detection and monitoring of biological invasions. In this study, we proposed and assessed the efficiency of newly created primer sets for the genetic identification of non-indigenous species (NIS) of fishes in the Volga basin based on: (a) a “long” fragment of cytochrome c oxidase subunit one of the mitochondrial gene (COI) (0.7 kb), used in “classical” DNA barcoding; (b) a short 3’-fragment (0.3 kb) of COI, suitable for use in high-throughput sequencing systems (i.e., for dietary analysis); (c) fragment of 16S mitochondrial rRNA, including those designed to fill the library of reference sequences for work on the metabarcoding of communities and eDNA studies; (d) a fragment of 18S nuclear rRNA, including two hypervariable regions V1-V2, valuable for animal phylogeny. All four sets of primers demonstrated a high amplification efficiency and high specificity for freshwater fish. Also, we proposed the protocols for the cost-effective isolation of total DNA and purification of the PCR product without the use of commercial kits. We propose an algorithm to carry out extremely cheap studies on the assessment of biological diversity without expensive equipment. We also present original data on the genetic polymorphism of all mass NIS fish species in the Volga-Kama region. The high efficiency of DNA identification based on our primers is shown relative to the traditional monitoring of biological invasions.

The data on Electronic Programmable Complex Fish-protecting facility of electric principle (EP EPRCFF) impact on gonads and gametogenesis of four abundant carp species (Cyprinidae) is given. Based on cytological and histological analysis of gonads from electro-treated fishes, an estimate of fishes’ fertility is made.

Water fleas (Crustacea: Cladocera) of the Family Bosminidae have been studied since the founding of paleolimnology and freshwater ecology. However, one species,Bosminopsis deitersi, stands out for its exceptional multicontinental range and broad ecological requirements. Here we use an integrated morphological and multilocus genetic approach to address the species problem inB. deitersi. We analyzed 32 populations ofB. deitersis. lat. Two nuclear and two mitochondrial loci were used to carry out the bGMYC, mPTP and STACEY algorithms for species delimitation. Detailed morphological study was also carried out across continents. The evidence indicated a widely distributed cryptic species in the Old World (Bosminopsis zernowi) that is genetically divergent fromB. deitersis.str. We revised the taxonomy and redescribed the species in this complex. Our sampling indicated thatB. zernowihad weak genetic differentiation across its range. A molecular clock and biogeographic analysis with fossil calibrations suggested a Mesozoic origin for theBosminopsis deitersigroup. Our evidence rejects the single species hypothesis forB. deitersiand is consistent with an ancient species group (potentially Mesozoic) that shows marked morphological conservation. The family Bosminidae, then, has examples of both rapid morphological evolution (HoloceneBosmina), and morphological stasis (Bosminopsis).

The biodiversity distribution patterns and their formation history in continental waters are studied based on some model groups such as Daphnia O.F. Müller (Crustacea: Cladocera). Most publications on this genus concern the subgenus Daphnia (Daphnia) while representatives of the subgenus Daphnia (Ctenodaphnia), inhabiting mainly temporary waters, are poorly studied. We found a new species of the D. (C.) sinensis complex in the deserts of the Arabian Peninsula, and our discovery allows us to resolve some problems concerning the history of these daphniids in the northern hemisphere. A formal description, illustrations (including numerous SEM photos) and a differential diagnosis of D. (C.) arabica Neretina, Al Neyadi & Hamza sp. nov. are provided. Phylogeny of D. (C.) similis complex is reconstructed based on three mitochondrial genes (12S, 16S and COI); a haplotype network based on short 12S fragments is also constructed. A monophyletic D. (C.) sinensis within the D. (C.) similis complex includes three earlier-derived locally distributed members: D. (C.) similoides, D. (C.) inopinata and D. (C.) arabica sp. nov. Our data suggest an old (Late Mesozoic) Gondwanan origin of the D. (C.) sinensis group and its Caenozoic differentiation in North Africa and the Middle East. This region then became a center of subsequent dispersion of D. (C.) sinensis through the whole of Eurasia and Africa during the Miocene and subsequent epochs. Interestingly, our scheme of the D. sinensis group dispersion has a well-known analogue: it is comparable to that suggested for earlier human migration from Africa through the Arabian Peninsula and the Middle East to the rest of Eurasia.

Background: Water fleas (Crustacea: Cladocera) of the Family Bosminidae have been studied since the founding of paleolimnology and freshwater ecology. However, one species, Bosminopsis deitersi, stands out for its exceptional multicontinental range and broad ecological requirements. Results: Here we use an integrated morphological and multilocus genetic approach to to address the species problem in B. deitersi. We analyzed 32 populations of B. deitersi s. lat. Two nuclear and two mitochondrial loci were used to carry out the bGMYC, mPTP and STACEY algorithms for species delimitation. Detailed morphological study was also carried out across continents. The evidence indicated a widely distributed cryptic species in the Old World (Bosminopsis zernowi) that is genetically divergent from B. deitersi s.str. We revised the taxonomy and redescribed the species in this complex. Our sampling indicated that B. zernowi had weak genetic differentiation across its range. A molecular clock and biogeographic analysis with fossil calibrations suggested a Mesozoic origin for the Bosminopsis deitersi group. Conclusions: Our evidence rejects the single species hypothesis for B. deitersi and is consistent with an ancient species group (potentially Mesozoic) that shows marked morphological conservation. The family Bosminidae, then, has examples of both rapid morphological evolution (Holocene Bosmina), and morphological stasis (Bosminopsis).

Our analysis of Alona cf. affinis (Cladocera: Chydoridae) populations from European Russia, Siberia and Far East of Russia bearing denticles at the posteroventral corner, based on both their morphology and genetic study considering variability of mitochondrial COI and 16S and nuclear 18S genes, revealed that they belong to a separate taxon described here as Alona sibirica sp. nov. Previously populations with denticles at the posteroventral corner were recorded from Sweden, Finland, Ukraine, European Russia, Kyrgyzstan and Mongolia, but never reported outside the temperate regions of Eurasia, so A. sibirica sp. nov. is presumably the only species of the A. affinis group with denticles at the posteroventral corner of the valves. The primary distribution area of the new species is North-East Palaearctic, while Eastern Europe and Central Asia are the areas of the species penetration, where it is less common and frequently coexisting with A. affinis s. str.

Most studies of water flea (Crustacea: Cladocera) invasions are concentrated on a few taxa with an obvious harmful influence on native ecosystems, while our knowledge of cases of anthropogenic introduction with not-so-obvious consequences, in most other taxa, is poor. We found in the Volga basin (European Russia) a population that contained D. curvirostris Eylmann, 1887 and its hybrids with D. korovchinskyi Kotov et al. 2021. The latter taxon is endemic to the Far East and it has appeared in the Volga basin as a result of past human-mediated transportation. The population from Bakhilovo is represented by two strongly different groups of the COI haplotypes belonging, respectively, to (1) D. curvirostris and (2) D. korovchinskyi. We detected SNPs in the position 60 of the HSP-90ex3 locus and in the 195 positions of 28S rRNA locus, which differentiate two species. Part of the specimens from Bakhilovo belonged to D. curvirostris s.str., demonstrating homozygote SNP sites in two loci, but two specimens had heterozygote SNP sites in both nuclear loci. They belong to D. curvirostris x korovchinskyi hybrids. Most morphological traits of the females were characteristic of D. curvirostris. We found in some specimens some characters which could suggest their hybrid status, but this opinion is a hypothesis only, which needs to be checked on more ample material. The exact hybrid system in this pond is not known. Moreover, we have no evidences of sexual reproduction of the hybrids, they could reproduce by parthenogenesis only as is known for hybrids of the D. pulex group, or continuously crossing with parents like some members of D. longispina group. However, poor parental D. korovchinskyi was not detected in the pond either morphologically or genetically. The exact vector of its past anthropogenic transportation to the Volga is unknown. Most probably, just ephippia of D. korovchinskyi were translocated replaced from the Khabarovsk Territory to the Samara Area somehow. This is the first report on hybrids within the D. curvirostris species complex. Here, we demonstrated that accurate studies with deep resolution increase the number of revealed cryptic invasions. We expect that the number of revealed cases of cryptic interspecific invasions will grow rapidly.

The paper provides information on alien species of fish caught in the coastal waters of the Volga and Kama river reservoirs. The material was collected during complex ship expeditions of the IBIW RAS in 2005-2017. We have identified habitats and estimated the relative abundance of mass alien species of the Volga-Kama region.

We found a Holarctic microcrustacean Daphnia galeata Sars, 1863 (Cladocera: Daphniidae) in the Lower Lakes of South Australia. This taxon was never detected in continental Australia before. Its identity was confirmed by the sequences of mitochondrial COI, 12S and 16S and nuclear 18S and 28S genes. A maximum likelihood tree from a dataset from combining 12S + 16S mitochondrial sequence and a split network of the COI haplotypes are provided, but resolution of both genes is not sufficient to reveal the exact region of the Holarctic from where D. galeata was introduced to Australia; the vector of its invasion also is unknown. We hypothesize that appearance of D. galeata in the Lower Lakes of the Murray River is related to a recent anthropogenic eutrophication of water bodies in this region, keeping in mind that examples of successful invasion of some European lakes by D. galeata after their eutrophication are well-known. We also hypothesize that establishment of this non-indigenous taxon populations in Australia might have a strong negative impact on native lake biota.

The biodiversity and the biogeography are still poorly understood for freshwater invertebrates. The crustacean Chydorus sphaericus-brevilabris complex (Cladocera: Chydoridae) is composed of species that are important components of Holarctic freshwater food webs. Recent morphological and genetic study of the complex has indicated a substantial species diversity in the northern hemisphere. However, we know little of the geographic boundaries of these novel lineages. Moreover, a large section of the Palearctic remains unexamined at the genetic level. Here we attempt to address the biodiversity knowledge gap for the Chydorus sphaericus group in the central Palearctic and assess its diversity and biogeographic boundaries. We sequenced nuclear (ITS-2) and mitochondrial (COI) gene regions of Chydorus specimens across the Palearctic and compared them with already available Holarctic sequences. We detected six main clades in the C. sphaericus group in the Palearctic, of which two of the groups are novel. Three of the more divergent clades are geographically widespread. The central portion of Eurasia (the Yenisey River basin) appears to be a narrow zone of secondary contact for phylogroups that expanded from European and Beringian refugia. As such, the previously unsampled central Palearctic represents an important region for understanding the evolutionary consequences of Pleistocene climatic oscillations on the Chydorus sphaericus group.

Species of the genus Daphnia O.F. Muller, 1785 (Cladocera: Daphniidae) have become very important models in evolutionary biology research. Previous morphological and genetic evidence suggests that numerous closely related “species groups” exist within the subgenus Daphnia ( Ctenodaphnia ) Dybowski & Grochowski, 1895, containing both described and undescribed species. The Daphnia similis group is among these species groups. The aim of the present paper is to revise the taxonomy of the Daphnia ( Ctenodaphnia ) similis group in the Old World with both morphological and genetic evidence (based on mitochondrial COI and 12S rRNA genes). We found that there are at least four species in the Old World D. similis species group: D. similis Claus, 1876; D. sinensis Gu, Xu, Li, Dumont et Han, 2013; D. similoides Hudec, 1991 and D. inopinata sp. nov. These four taxa of the similis- group, confused previously with D. similis, have different distributional ranges in the Old World, from extremely wide, spanning several biogegraphic regions (as D. sinensis ), to regional endemics ( D. similoides ) and even species known so far from a single locality ( D. inopinata sp. nov.). The Daphnia similis group provides another example in the cladocerans whereby the study of males yields more valuable characters for taxonomy than the study of parthenogenetic females.