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In this work, we present an integrative revision of the Lymnaeidae from the northeastern margin of Asia (Far East Russia, Japan, and Korea) and Alaska. According to our results, 14 native species inhabit this region, belonging to eight genera in two subfamilies (Lymnaeinae: Dallirhytis , Galba , Walhiana , Ladislavella , and Lymnaea ; and Amphipepleinae: Kamtschaticana , Orientogalba , and Radix). Four of these species are new to science and three of them are described in this paper. Additionally, three established alien species are recorded from Japan (Pseudosuccinea columella , Galba schirazensis , and Galba humilis). The Japanese Archipelago represents an evolutionary hotspot of pond snail diversity, encompassing seven native species, three of which are endemic. The faunal connections between North America and northeastern Asia are discussed in the context of historical biotic interchange across the Beringian Land Bridge. Two cold-tolerant pond snails share high-latitude but localized ranges, being endemic to the Beringian Arctic: Dallirhytis atkaensis (Chukchi Peninsula, Alaska, and Aleutian Islands) and Walhiana arctica comb. nov. (Alaska). Our findings indicate that the Beringian Land Bridge has played a role in freshwater faunal exchanges between northeastern Asia and western North America. [ABSTRACT FROM AUTHOR]

The subfamily Sphaeriinae is a diverse and ecologically significant group of freshwater invertebrates, playing a keystone role in the energy flow and nutrient cycling in aquatic ecosystems. Despite a long history of its study, the taxonomic structure and species content of this group are a matter of ongoing disputes between malacologists. We clarify the taxonomy, distribution, and evolutionary biogeography of the Sphaeriinae around the world based on the largest dataset of DNA sequences of these clams ever accumulated, which includes the data on specimens collected from various continents and countries around the globe. Our 16S rRNA and two-locus phylogenies reveal that the Sphaeriinae is a monophyletic group, containing at least seven genus-level clades: Sphaerium Scopoli, 1777, Pisidium C. Pfeifffer, 1821 (s.s.), Euglesa Jenyns, 1832, Odhneripisidium Kuiper, 1962, Conventus Pirogov & Starobogatov stat. nov. 1974, 'Pisidium' sterkianum group, and Hindupisidium Vinarski & Bespalaya gen. nov. Our 16S rRNA phylogenetic tree contains 80 well-supported clades corresponding to the putative species-level taxa. Four species new to science are described here: Euglesa kolymensis Bespalaya, Aksenova & Bolotov sp. nov. , Euglesa kyrgyzica Bespalaya, Aksenova, Kondakov & Palatov sp. nov. , Euglesa moroccana Bespalaya, Vinarski, Aksenova, Mabrouki, Kondakov & Palatov sp. nov. , Odhneripisidium caucasus Bespalaya, Vinarski, Aksenova, Kondakov & Palatov sp. nov. Our fossil-calibrated phylogeny and generalized biogeographic model indicate that the most recent common ancestor of the Sphaeriidae could have originated somewhere within a broad area covering China near the Lower Cretaceous boundary. [ABSTRACT FROM AUTHOR]

Currently, the parasitic and endosymbiontic fauna of Corbicula clams remain poorly studied throughout their range. Here, using samples from the Mekong basin, we describe two Symbiocloeon species new to science: Symbiocloeon corbiculinus sp. nov. and Symbiocloeon laoensis sp. nov. Our results and a review of available published data indicate that freshwater bivalve-associated mayflies are narrow host specialists, being associated with one or a few closely related species of freshwater bivalves. The bivalve-associated mayfly larvae have several specific morphological traits compared with free-living species, which include a reduction of integument chitinization and a significant reduction of the surface structures on segments. An increase in area of the respiratory surface of larval tergalia was also recorded. The possible positive and negative effects of mayflies on the clam hosts are discussed. This study is an example of the many possible hidden associations between aquatic species that remain to be described. [ABSTRACT FROM AUTHOR]

Currently, the validity of many nominal bivalve species of the genus Corbicula endemic to the Russian Far East and South Korea needs a critical reassessment. In this study, we clarify the taxonomic status of Corbicula species of this area based on a combination of molecular genetic, conchological and anatomical data. According to our results, four Corbicula lineages, corresponding to the nominal species Corbicula japonica , Corbicula elatior , Corbicula leana and Corbicula fluminea , can be delineated in samples collected in the Primorye and Khabarovsk regions of Russia and South Korea. Two species endemic to the Russian Far East (i.e. Corbicula finitima and Corbicula lindholmi) are considered here as junior synonyms of the species C. japonica , which is widely distributed in estuarine habitats around the Japanese Archipelago, Sakhalin Island, southern Kurile Islands, Primorye and Khabarovsk regions, Korean Peninsula and China. Three nominal species described from the Lower Amur basin (Corbicula amurensis , Corbicula nevelskoyi and Corbicula sirotskii) appeared to be synonyms of C. elatior , whose range covers the Korean Peninsula, Primorye and Khabarovsk regions and, perhaps, China. We delineated several colour morphs of C. fluminea and C. japonica. The distinctness between these colour morphs can be attributed to both heritable and environmental factors. [ABSTRACT FROM AUTHOR]