Larisa Prozorova

Conquest of the deep, old and cold: an exceptional limpet radiation in Lake Baikal.

Lake Baikal is the deepest, oldest and most speciose ancient lake in the world. The lake is characterized by high levels of molluscan species richness and endemicity, including the limpet family Acroloxidae with 25 endemic species. Members of this group generally inhabit the littoral zone, but have been recently found in the abyssal zone at hydrothermal vents and oil-seeps. Here, we use mitochondrial and nuclear data to provide a first molecular phylogeny of the Lake Baikal limpet radiation, and to date the beginning of intra-lacustrine diversification. Divergence time estimates suggest a considerably younger age for the species flock compared with lake age estimates, and the beginning of extensive diversification is possibly related to rapid deepening and cooling during rifting. Phylogenetic relationships and divergence time estimates do not clearly indicate when exactly the abyssal was colonized but suggest a timeframe coincident with the formation of the abyssal in the northern basin (Middle to Late Pleistocene).

Spirochetes in gastropods from Lake Baikal and North American freshwaters: new multi-family, multi-habitat host records

We describe the first records of spirochetes in the gut of fourteen species of continental gastropods from a range of habitats and representing six families (Amnicolidae, Baicaliidae, Bithyniidae, Pyrgulidae, Lithoglyphidae and Benedictiidae). The bacteria were mainly found in the crystalline style sac, as has been reported in marine bivalves. The surveyed habitats include water bodies in North America and Eurasia, including deep water hydrothermal vent and gas hydrate zones in Lake Baikal. Spirochetes were present both in mature and young snails, but were not detected in embryos before hatching, indicating lateral transfer. The surveyed gastropods range in trophic strategy, including phyto-, detrito- and bacteriophagous grazers and filter feeders. Our results indicate that spirochetes are commensal in the surveyed gastropods with potential limited benefit and no detriment to the host animal. We suggest that the specialized internal habitat of the crystalline style sac in molluscs is likely to reveal unrecognized spirochete diversity that will shed new light on gastropod trophic ecology and spirochete diversity.

Parallel evolution of passive and active defence in land snails

Predator-prey interactions are major processes promoting phenotypic evolution. However, it remains unclear how predation causes morphological and behavioural diversity in prey species and how it might lead to speciation. Here, we show that substantial divergence in the phenotypic traits of prey species has occurred among closely related land snails as a result of adaptation to predator attacks. This caused the divergence of defensive strategies into two alternatives: passive defence and active defence. Phenotypic traits of the subarctic Karaftohelix land snail have undergone radiation in northeast Asia, and distinctive morphotypes generally coexist in the same regions. In these land snails, we documented two alternative defence behaviours against predation by malacophagous beetles. Furthermore, the behaviours are potentially associated with differences in shell morphology. In addition, molecular phylogenetic analyses indicated that these alternative strategies against predation arose independently on the islands and on the continent suggesting that anti-predator adaptation is a major cause of phenotypic diversity in these snails. Finally, we suggest the potential speciation of Karaftohelix snails as a result of the divergence of defensive strategies into passive and active behaviours and the possibility of species radiation due to anti-predatory adaptations.

Large bivalve molluscs (Bivalvia, Unioniformes) of Lake Baikal

Large bivalves represented in Lake Baikal by anodontines of the genus Colletopterum Bgt. are revised on the basis of a morphological examination of specimens preserved in Zoological Institute RAS, St. Petersburg (ZISP) and in Institute of Biology and Soil Science Far east Branch RAS, Vladivostok (IBSS). Shell shape, shape of valves, curvature of the frontal section of the valves, location of umbones and the ratio of shell width to height at the ligament were all taken into consideration. Results indicate that Lake Baikal is inhabited by five species of Colletopterum instead of only the formerly known subspecies C. ponderosum sedakovi (Siemaschko), which we regard as a synonym of C. anatinum (L.) following reidentification of the lectotype of the former. Three European–Siberian species: C. anatinum, C. piscinale (Nilsson), and C. nilssonii (Kuester), are recorded from the Baikal drainage for the first time.Specimens of large Baikalian bivalves in the ZISP collection bearing subspecies names by W. Dybowski are recognized as a mixture of different species. All type specimens were examined to establish their identity. It is concluded that C. sorensianum (W. Dybowski in B. Dybowski, 1913) (syn.: Anodonta complanata sorensiana W. Dybowski in B. Dybowski, 1913; A. cellensis sorensis W. Dybowski erroneous spelling by Shadin, 1938; A. cellensis ssorensis W. Dybowski erroneous spelling by Shadin, 1952) is a valid species characterized by having the flattest shell. Other subspecies names proposed by W. Dybowski’s are regarded as junior synonyms of Siberian–European species: C. piscinale (Nilsson, 1822) (syn.: A. cellensis selengensis W. Dybowski in B. Dybowski, 1913; A. nova W. Dybowski, 1913), C. anatinum (L., 1758) (syn.: A. sedakovi Siemaschko, 1848); A. piscinalis sorica W. Dybowski in B. Dybowski, 1913); C. ponderosum (Pfieffer, 1825); C.nilssonii (Kuester, 1842).The key to identification of Baikalian large bivalves are also provided.

Endangered freshwater limpets in Japan are actually alien invasive species

Currently, many species are facing the risk of extinction, as it one of the most serious conservation issues. Many conservation programs have evolved to prevent species extinction; however, developing these strategies may prove to be difficult for the species itself, which includes different cryptic species. In this paper, we document the invasion of non-native cryptic species of ancylin limpets, Ferrissia californica, with a molecular phylogenetic analysis. Three species (F. nipponica, F. japonica, Gundlachia japonica) have been described as native, whereas the present analysis shows that most of them are actually non-native F. californica, having been introduced from North America and spreading throughout Japan. In addition, we found a few subpopulations of the cryptic native species of the ancylin limpets, though the native limpet species is very rare, and has limited distribution. The conservation status assigned to ancylin limpets on the Japanese red list is problematic, because F. japonica is listed as an endangered species. All individuals identified as F. japonica are of F. californica, so the current red list treats invasive non-native species as endangered. Reassessment of the conservation status of native species and an estimation of the impact of non-native species is required to better delineate these limpet species by genetic markers.

Taxonomy and Diversity of Freshwater Bivalve Mollusks (Bivalvia) of China (Based on Analysis of the Catalog by He and Zhuang, 2013)

The diversity of freshwater Bivalvia in China was assessed on the basis of critical analysis of original and published data on the fauna, morphology, taxonomy, and molecular genetics of this group. The taxonomic composition of the following genera has been considered in depth: Anemina Haas 1969, Cristaria Schumacher 1817, Sinanodonta Modell 1944, Lanceolaria Conrad 1853, Middendorffinaia Moskvicheva et Starobogatov 1973, Nodularia Conrad 1853, Unio Philipsson in Retzius 1788, Inversidens Haas 1911, Sphaerium Scopoli 1777, Pisidium Pfeiffer 1821, Odhneripisidium Kuiper 1962, and Euglesa Leach in Jenyns 1832 = Cyclocalyx Dall 1905. No fewer than 170 bivalve species were demonstrated to occur in the freshwater areas of China. Underestimation of the Bivalvia species abundance in previous studies, including the latest catalog of the Chinese Bivalvia (He and Zhuang, 2013), may be accounted for mostly by inadequate use of morphological methods and limited faunistic data, as well as a little number of taxonomic works supported by molecular data. Both the generic and specific compositions of the Chinese Unioniformes and Luciniformes have been significantly extended and updated. Based on a complex study of conchological characters, the following synonymy was established for three species: Sinanodonta qingyuani He et Zhuang 2013 = S. woodiana (Lea 1834) syn. n., Lanceolaria yueyingae He et Zhuang 2013 = L. eucylindrica C. Lin 1962 syn. n., Acuticosta jianghanensis He et Zhuang 2013 = Nodularia douglasiae (Griffith et Pidgeon 1833) syn. n.

Modern distribution of gastropod mollusks of the family Viviparidae (Caenogastropoda) in continental water bodies of Eurasia

Modern distribution of ovoviviparous mollusks of the genera Viviparus and Contectiana of the family Viviparidae has been considered for the first time in general for Eurasia. Original, museum, and literature data that have been accumulated to date on the spread of these Palaearctic genera were summarized and analyzed. The modern boundaries of the distribution of Viviparidae in water bodies of the region were established, and biogeographical changes were mentioned that have occurred over the past 40 years. Information on the habitats of Viviparus and Contectiana are presented in general for Eurasia and in more detail for Ukraine. It was revealed that, with the overall stability of the habitats of these Palaearctic genera, there are fluctuations in the distribution of their representatives in the basins of some rivers in Eurasia and acquisition of new and/or loss of former habitats in Eastern Europe and Western Siberia. The uneven distribution of these genera on the territory of Ukraine and their absence in the area of the Sea of Azov coast, which are not associated with the presence of geographical barriers, were shown.

Nematode communities in the Sai Gon River harbors in relation to tributyltin concentrations

The impact of toxic tributyltin (TBT) compounds was investigated on free-living nematode communities in the Sai Gon River. Samples were collected from 11 harbor stations downstream of the Sai Gon river plus one upstream station during the dry and rainy seasons. The results showed that all butyltin compound (mono-, di-, and tri) concentrations were relatively low compared to historical data from the same or adjacent estuaries, supporting the effectiveness of the 2009 ban on these products as antifouling. Nematode communities were typical for oligohaline regions showing a high spatial and temporal variability in abundance and diversity. Nematode community composition clearly differed between the two seasons, with the nematode communities being less variable in the rainy season compared to the dry season, while nematode communities differed significantly between stations. TBT values were still significantly negative correlated with nematode densities and selective deposit feeders during the dry season, partly confirming earlier experimental results on the response of nematodes to TBT. The historical presence of TBT contamination can possibly have caused a long-term impact on nematode communities in the Sai Gon river sediment, reflected in depressed densities during the dry season.

Molecular phylogeny of glacial relict species: a case of freshwater Valvatidae molluscs (Mollusca: Gastropoda) in North and East Asia

The study of glacial relict species has been focused on understanding how the biogeographic patterns of species have developed. A number of studies using phylogenetic and population genetics approaches have been conducted for terrestrial glacial relict species, and the mechanisms of their formation have been elucidated. On the other hand, less focus has been placed on glacial relict species inhabiting freshwater systems. In particular, stable lakes can serve as refugia during a glacial period, but research studies on freshwater relict species inhabiting lakes have not been well conducted. In order to clarify the mechanism of the glacial relict species in freshwater, we conducted a molecular phylogeny analysis, divergence time estimation, and a biogeographic reconstruction on freshwater Valvatidae molluscs, which have been considered as a glacial relict in the Japanese Archipelago. Our study shows that the valvatid fauna in the Japanese Archipelago was produced by multiple dispersal events from the Asian continent and by vicariance events during the period of the Pliocene–Quaternary glaciation. It includes multiple relict species that survived interglacial periods in different lakes. These findings suggest that the lakes can serve as refugia not only during glacial periods, but also during interglacial periods.

A review of the Lake Baikal limpets, family Acroloxidae Thiele, 1931 (Mollusca: Pulmonata: Hygrophila), based on type specimens, with keys to the genera

We provide a comprehensive synopsis of Lake Baikal limpets, including summaries of their taxonomy and nomenclature, with emphasis on the identification of type species. We provide colour photographs of the type specimens of 24 valid species of the family Acroloxidae, including 22 species in 4 endemic or subendemic Baikalian genera, Pseudancylastrum, Frolikhiancylus, Gerstfeldtiancylus, and Baicalancylus, and 2 Siberian–Amur species in the Holarctic genus Acroloxus inhabiting shallow bays of Lake Baikal. Most of the species were described by the Russian malacologist Yaroslav I. Starobogatov between 1989 and 1991. The type species are stored in the collections of the Zoological Institute of the Russian Academy of Sciences (Saint Petersburg, Russia), the Limnological Institute of the Siberian Branch of the Russian Academy of Sciences (Irkutsk, Russia), the Zoological Museum of the Ivan Franko National University of Lviv (Ukraine), and the Freie Universität Berlin (Germany). We also present photographs of the holotypes of 2 species described by Starobogatov in 1989 and later synonymized. We provide topotype SEM images of species for which the type specimens are unavailable. Images of the teleoconch ultrastructure of 14 species as well as protoconchs of 11 species have not been published previously. Most of the topotypes are kept in collections of the Senckenberg Naturmuseum (Frankfurt am Main) and the Limnological Institute SB RAS. For each species, we describe their synonymy, type locality, type series, vertical and geographic distribution in Baikal, substrate preferences, ecology in brief (if at all), history of the usage of the name, and taxonomic remarks. We present a new identification key to Gerstfeldtiancylus spp. Specifically, we propose new characters, such as radula and jaw structure details, protoconch sculpture types, shell adductor topography, and relative sizes of parts of the male copulatory organ, in addition to traditional characters, such as teleoconch proportions. Identification keys to Pseudancylastrum and Baicalancylus spp. include well-defined species only.