Morphological and Genetic Variability in <i>Radix auricularia</i> (Mollusca: Gastropoda: Lymnaeidae) of Lake Baikal, Siberia: The Story of an Unfinished Invasion into the Ancient Deepest Lake

This article aims to reconstruct the invasion of the ear-shaped pond snail, Radix auricularia (Linnaeus, 1758), to Lake Baikal, East Siberia. This species is widely distributed in the Palaearctic and Northern America, and since the early 20th century has formed abundant and sustained populations in Lake Baikal. The data provided on the morphological and genetic variability of R. auricularia help to better describe and delineate the species. With an integrative approach involving morphological and molecular data, we improved the knowledge of the intraspecific variability of R. auricularia in the most important characteristics used for its determination. Molecular sequences of nuclear spacer fragment ITS-2 and mitochondrial gene fragment cyt–b were obtained from 32 individuals of Radix (including seven outgroup Radix species) collected from various parts of Lake Baikal and adjacent waterbodies and compared with sequences of 32 individuals of R. auricularia from different regions of the Palaearctic as well as with individuals determinated as R. intercisa from Lake Baikal, R. iturupica from the Kurile Islands, R. ussuriensis from the Khabarovsk region, R. narzykulovi from Tajikistan, and R. schubinae from the Amur region. Molecular genetic analyses revealed that all specimens collected from Lake Baikal belong to R. auricularia. There are no genetically distinct groups of snails that would correspond to two morphospecies previously recorded in Lake Baikal (e.g., R. auricularia s. str. and R. intercisa). Variability of the characteristics that are commonly used for species identification (shell morphology, mantle pigmentation, shape and position of the bursa copulatrix, length and position of the bursa duct, length ratio of preputium to penial sheath) were found in individuals analysed with molecular genetics to be broader than recognised in the current literature. Some shells of R. auricularia collected from Lake Baikal resemble shells of another lymnaeid species, R. balthica, and without molecular assessment can be confused with the latter. Geometric morphometric analysis of more than 250 shells revealed no observed hiatus between Baikalian and non-Baikalian R. auricularia. The probable stages and pathways of R. auricularia invasion to Lake Baikal’s ecosystem are outlined and discussed. Factors such as global climate warming and human activity stimulated and facilitated the ongoing dispersal of ear pond snails within Lake Baikal

Ecology, shell morphology, anatomy and sperm ultrastructure of the caenogastropod Pyrgula annulata, with a discussion of the relationship between the 'Pyrgulidae' and Caspian and Baikalian rissooideans

The composition of the Pyrgulidae and its relationships to other member families of the caenogastropod superfamily Rissooidea are examined after a consideration of new anatomical (including gross anatomy, sperm ultrastructure), conchological (including protoconch features), ecological, biogeographical and palaeontological data and a re-evaluation of existing literature. Pyrgulidae can be distinguished from hydrobiids unequivocally only with the aid of the radula. Sperm ultrastructural features suggest a very close relationship between the Pyrgulidae, the Hydrobiidae and the Bithyniidae (in fact no family-diagnostic sperm characters can be found to separate these three taxa). Based upon neontological and fossil evidence it is likely that pyrgulids represent a Miocene offshoot from a paratethyal hydrobiid lineage. Pyrgulids may also represent the stock from which the baicaliids arose, in which case the Pyrgulidae must be considered a paraphyletic group. The huge biogeographic gap between the Caspian Sea and Lake Baikal is to some extent bridged by the finding of a Neogene pyrgulid from the Altai Mountains. An alternative scenario for the origin of baicaliids is presented

Jelly-like Microbial Mats over Subsurface Fields of Gas Hydrates at the St. Petersburg Methane Seep (Central Baikal)

<div><p>Jelly-like microbial mat samples were collected from benthic surfaces at the St. Petersburg methane seep located in Central Baikal. The concentrations of certain ions, specifically chloride, bromide, sulphate, acetate, iron, calcium, and magnesium, were 2–40 times higher in the microbial mats than those in the pore and bottom water. A large number of diatom valves, cyanobacteria, and filamentous, rod-shaped and coccal microorganisms were found in the samples of bacterial mats using light, epifluorescence and scanning microscopy.Comparative analysis of a 16S rRNA gene fragment demonstrated the presence of bacteria and archaea belonging to the following classes and phyla: Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, Verrucomicrobia, Cytophaga-Flavobacteria-Bacteroidetes, Cyanobacteria, and Euryarchaeota. The chemical composition and phylogenetic structure of the microbial community showed that the life activity of the mat occurs due to methane and its derivatives involved. Values of δ¹³C for the microbial mats varied from −73.6‰ to −65.8‰ and for animals from −68.9‰ to −36.6‰. Functional genes of the sequential methane oxidation (<i>pmoA</i> and <i>mxaF</i>) and different species of methanotrophic bacteria inhabiting cold ecosystems were recorded in the total DNA. Like in other psychroactive communities, the destruction of organic substances forming formed as a result of methanotrophy, terminates at the stage of acetate formation in the microbial mats of Lake Baikal (1,400 m depth). Its further transformation is limited by hydrogen content and carried out in the subsurface layers of sediments.</p></div

Amazing Discoveries of Benthic Fauna from the Abyssal Zone of Lake Baikal

Lake Baikal is a natural laboratory for the study of species diversity and evolution, as a unique freshwater ecosystem meeting the all of the main criteria of the World Heritage Convention. However, despite many years of research, the true biodiversity of the lake is clearly insufficiently studied, especially that of deep-water benthic sessile organisms. For the first time, plastic waste was raised from depths of 110 to 190 m of Lake Baikal. The aim of this study was to examine the biological community inhabiting the plastic substrate using morphological and molecular genetic analysis. Fragments of plastic packaging materials were densely populated: bryozoans, leeches and their cocoons, capsules of gastropod eggs, and turbellaria cocoons were found. All the data obtained as a result of an analysis of the nucleotide sequences of the standard bar-coding fragment of the mitochondrial genome turned out to be unique. Our results demonstrate the prospects for conducting comprehensive studies of artificial substrates to determine the true biodiversity of benthos in the abyssal zone of Lake Baikal