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Diverse associations of freshwater sponges with molluscs were recently described from the Xingu River, Amazon Basin. However, such associations in other parts of the world are almost unknown. Here, we report on the discovery of epifaunal associations of a freshwater sponge (Corvospongilla, Spongillidae) with a byssus‐attaching clam (Limnoperna, Mytilidae) and a freshwater mussel (Hyriopsis, Unionidae) in tropical Asia (Mun River, Thailand). We used this association as a model system to show how the application of an integrative taxonomic approach can change modern views on the taxonomic status and biogeographic affinities of tropical invertebrates in a rather small sample. The freshwater sponge from the Mun River morphologically corresponds to the nominal taxon Corvospongilla siamensis but it is identical to Corvospongilla ultima from the Kaladan River, western Myanmar, based on the sequences of five DNA markers and the PTP species delimitation modeling. Hence, the first species is considered here to be a junior synonym of C. ultima. Conversely, the Limnoperna clam from the Mun River is found to be distant phylogenetically from the invasive golden mussel Limnoperna fortunei based on the sequences of three DNA markers. We therefore restore Limnoperna siamensisstat. rev. as a valid species. Our time‐calibrated multi‐locus phylogeny reveals that the split between L. siamensis and L. fortunei most likely occurred at the Miocene—Pliocene boundary. Finally, the freshwater mussel Hyriopsis khoratensis is an abundant species endemic to the Mun River. Our novel data highlight that associations of freshwater sponges with bivalves are present in Asia but were historically overlooked there and that the Mekong's sponge‐mollusc association can be considered analogous to those discovered in South America. [ABSTRACT FROM AUTHOR]

Freshwater pearl mussels (Bivalvia: Margaritiferidae) are among the most imperiled groups of animals globally. While the parasites and symbionts of the Margaritiferidae are rather poorly known, these mussels were thought to be free of parasitic mites (Acari: Unionicolidae: Unionicola). Here, we report on the discovery of a mite species being associated with the endangered freshwater pearl mussel Gibbosula laosensis (Lea, 1863) from Myanmar. This species, Unionicola (Gibbosulicola) sellasubgen. & sp. nov., morphologically resembles mites belonging to the subgenera Coelaturicola and Fulleratax (African and Southeast Asian groups, respectively). Our novel discovery expands the host range of Unionicola mites and reveals that all freshwater mussel families of the order Unionida host these aquatic mites. Our phylogenetic research and available published data reveal that the mussel‐associated mite assemblage in Southeast and South Asia contains not less than 17 species and 8 subgenera. Currently, the regional taxonomic richness of this group seems to be largely underestimated. We found that mussel mites from Southeast Asia are narrow host specialists, which are known to occur in a single or a few closely related species belonging to one or two sister genera of freshwater mussels. Finally, our results indicate that mussel mites share generally restricted ranges and that their distribution patterns in Southeast Asia are largely congruent with the boundaries of biogeographic subregions delineated on the basis of phylogenetic studies of freshwater mussels. [ABSTRACT FROM AUTHOR]

North Sumatra's Lake Toba is a famous example of a supervolcano caldera, being the world's deepest and largest crater lake. It has been originated since the massive Toba eruption of 74,000 years ago that coincides with global environmental shifts and a significant bottleneck in the global human population. While the freshwater fauna of this lake does not share high levels of endemism, there is Corbicula tobae, an Asian clam species that was described as a taxon endemic to Lake Toba. Here we confirm the validity of this species using morphological, anatomical, and DNA‐based evidences, although the general species‐level concept for this genus is yet to be developed. Additionally, Corbicula leana, a widespread invasive species, was recorded from Lake Toba for the first time. These two species living in sympatry in Lake Toba appear to exploit different ecological niches within the lake. [ABSTRACT FROM AUTHOR]

The taxonomic position of three nominal species of lymnaeid snails placed by Kruglov & Starobogatov (1993) into the subgenus Lymnaea (Pacifimyxas) Kruglov & Starobogatov, 1985, has been re‐assessed based on a molecular genetic study of topotypic specimens and an examination of the type series and other materials available. It has been shown that the two species, Lymnaea (Pacifimyxas) magadanensis Kruglov & Starobogatov, 1985 and Lymnaea (Pacifimyxas) streletzkajae Kruglov & Starobogatov, 1985, are identical with the species Kamtschaticana kamtschatica (Middendorff, 1850) and must be treated as its junior synonyms. Hence, Pacifimyxas becomes a junior synonym of Kamtschaticana Kruglov & Starobogatov, 1984. The taxonomic identity of the third species of Pacifimyxas, Lymnaea (Pacifimyxas) perpolita, remains obscure, and this species is considered here as taxon inquirendum. Two other nominal species, Lymnaea aberrans (Westerlund, 1897) and Lymnaea middendorffi (W. Dybowski, 1904), have been synonymized with K. kamtschatica based on morphological and geographical evidence. The lectotype of Limnaea peregra var. middendorffi is designated. The actual level of species richness in the Beringian freshwater malacofauna may be 20–25% lower than it was determined on the basis of the traditional system. Some implications of this outcome for the biogeography of the Beringian freshwater fauna are discussed. [ABSTRACT FROM AUTHOR]