A global-scale screening of non-native aquatic organisms to identify potentially invasive species under current and future climate conditions

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium- and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a ‘very high risk’ of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate ‘rapid’ management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement

Segmental paleotetraploidy revealed in sterlet (Acipenser ruthenus) genome by chromosome painting

Backgroun

The rise and fall of the ancient northern pike master sex-determining gene

The understanding of the evolution of variable sex determination mechanisms across taxa requires comparative studies among closely related species. Following the fate of a known master sex-determining gene, we traced the evolution of sex determination in an entire teleost order (Esociformes). We discovered that the northern pike (Esox lucius) master sex-determining gene originated from a 65 to 90 million-year-old gene duplication event and that it remained sex linked on undifferentiated sex chromosomes for at least 56 million years in multiple species. We identified several independent species- or population-specific sex determination transitions, including a recent loss of a Y chromosome. These findings highlight the diversity of evolutionary fates of master sex-determining genes and the importance of population demographic history in sex determination studies. We hypothesize that occasional sex reversals and genetic bottlenecks provide a non-adaptive explanation for sex determination transitions

The rise and fall of the ancient northern pike master sex determining gene

The understanding of the evolution of variable sex determination mechanisms across taxa requires comparative studies among closely related species. Following the fate of a known master sex-determining gene, we traced the evolution of sex determination in an entire teleost order (Esociformes). We discovered that the northern pike (Esox lucius) master sex-determining gene originated from a 65 to 90 million-year-old gene duplication event and that it remained sex-linked on undifferentiated sex chromosomes for at least 56 million years in multiple species. We identified several independent species- or population-specific sex determination transitions, including a recent loss of a Y-chromosome. These findings highlight the diversity of evolutionary fates of master sex-determining genes and the importance of population demographic history in sex determination studies. We hypothesize that occasional sex reversals and genetic bottlenecks provide a non-adaptive explanation for sex determination transitions

Effect of microplastics on the activity of digestive and oxidative-stress-related enzymes in peled whitefish (Coregonus peled Gmelin) larvae

Microplastics (MPs) are emergent pollutants in freshwater environments and may impact aquatic organisms, including those of nutritional value. The specific activities of digestive and antioxidant enzymes can be used as good bioindicators of the potential effects of MPs on fish in case of waterborne MP contamination. In this study, we used fluorescent polystyrene microplastics (PS-MPs) to analyze the alterations in enzyme activities in larvae of Coregonus peled Gmelin (peled or Northern whitefish), one of the most valuable commercial fish species of Siberia. Our results indicate that peled larvae can ingest 2 µm PS microspheres in a waterborne exposure model. A positive correlation (rs = 0.956; p < 0.01) was found between MP concentration in water and the number of PS microspheres in fish guts, with no significant differences between 24 h and 6-day exposure groups. The ingestion of MPs caused alterations in digestive enzyme activity and antioxidant responses at the whole-body level. The presence of PS-MPs significantly stimulated (p < 0.05) the specific activity of α-Amylase and non-specific esterases in peled larvae after 24 h. However, a pronounced positive effect (p < 0.05) of MPs on the activity of pancreatic trypsine and bile salt-activated lipase was only found after 6 days of exposure compared to after 24 h. Intestinal membrane enzyme aminopeptidase N was also stimulated in the presence of PS-MPs after 6-day exposure. We also observed a significant increase in the specific activity of catalase in peled larvae after 6 days of exposure, which indicates the MP-induced modulation of oxidative stress. Taken together, these results highlight the potential impact of environmental MPs on northern commercial fish, their importance for estimating fish stocks, and the sustainability of freshwater ecosystems

New data on small lampreys of the genus Lethenteron (Petromyzontidae) of the Tom River, a typical habitat of the Siberian brook lamprey Lethenteron kessleri

The article presents data of morphological and molecular-genetic analyzes of small lampreys from the Tom River, a typical habitat of the Siberian brook lamprey Lethenteron kessleri (Anikin, 1905), as well as of one specimen of a large lamprey caught in the same period of the year in the Ob River. All studied specimens are similar in the structure of the dental apparatus to lampreys of the upper Ob tributaries and the upper Irtysh basin, and also correspond to the characteristics of Lethenteron camtschaticum. They have one haplotype of the mitochondrial cytochrome oxidase c subunit I gene, previously described for lampreys from the Ob River basin and the rivers of the White Sea basin. Currently, there is no reason to consider small lampreys of the Tom River as a valid species Lethenteron kessleri

Fish diversity in freshwater and brackish water ecosystems of Russia and adjacent waters

In the present paper, the history of fish faunistic and taxonomic knowledge is analyzed, and the freshwater and brackish water fish diversity in the territory of the Russian Federation and adjacent areas is examined. An overview of higher taxa and species is presented (3 classes, 26 orders, 100 families, and 317 genera), including a total of 719 native fish species (plus 36 introduced species, and also 16 species not yet recoded for Russian waters, but expected in the future, and 20 species that were previously removed from the ichthyofauna of Russia due to taxonomic changes; total number in all categories 791 taxa). The Russian water includes freshwater 353, brackish 329, diadromous 82, and amphidromous 27 species. A total of 103 endemic species in the native ichthyofauna adds to an endemism rate of 14, 3%. This study significantly increases the total number of fishes ecologically related to fresh and brackish waters of Russia. The native freshwater and brackish water ichthyofauna of the Russian Federation consists of approximately 4% of the global fish species. The fish diversity in selected river systems and lakes is also discussed, with respect to ecoregions, latitude and longitude, and compared with the fish faunas of Europe and North America (north of 50o N)

Macrozoobenthos diversity of the Middle Ob river tributaries

The data show quantitative and qualitative composition of macrozoobenthos of the 12 left-bank confluences of the Middle Ob. The research has documented the presence of various groups, such as Oligohaeta, Diptera, Odonata, Hirudinea, Tabanidae, Trichoptera and Mollusca. The chironomids, molluscs and leeches play a significant role in the generation of biomass in the surveyed streams, and the abundance mostly depends on chironomids, oligochaetes and leeches. In general, zoobenthos abundance ranges from 8.8 (the Shudelka river) to 1839.9 (the Kochebilovka river) ind./m2, biomass is from 0.08 (Tatosh river) to 8.37 (Lozunga river) g/m2. The amount and benthos biomass of the Middle Ob’s second-order tributaries is higher than in the first-order tributaries

Chromosome distribution of highly conserved tandemly arranged repetitive DNAs in the Siberian sturgeon (Acipenser baerii)

Polyploid genomes present a challenge for cytogenetic and genomic studies, due to the high number of similar size chromosomes and the simultaneous presence of hardly distinguishable paralogous elements. The karyotype of the Siberian sturgeon (Acipenser baerii) contains around 250 chromosomes and is remarkable for the presence of paralogs from two rounds of whole-genome duplications (WGD). In this study, we applied the sterlet-derived acipenserid satDNA-based whole chromosome-specific probes to analyze the Siberian sturgeon karyotype. We demonstrate that the last genome duplication event in the Siberian sturgeon was accompanied by the simultaneous expansion of several repetitive DNA families. Some of the repetitive probes serve as good cytogenetic markers distinguishing paralogous chromosomes and detecting ancestral syntenic regions, which underwent fusions and fissions. The tendency of minisatellite specificity for chromosome size groups previously observed in the sterlet genome is also visible in the Siberian sturgeon. We provide an initial physical chromosome map of the Siberian sturgeon genome supported by molecular markers. The application of these data will facilitate genomic studies in other recent polyploid sturgeon species