Conservation of freshwater bivalves at the global scale: diversity, threats and research needs

Bivalves are ubiquitous members of freshwater ecosystems and responsible for important functions and services. The present paper revises freshwater bivalve diversity, conservation status and threats at the global scale and discusses future research needs and management actions. The diversity patterns are uneven across the globe with hotspots in the interior basin in the United States of America (USA), Central America, Indian subcontinent and Southeast Asia. Freshwater bivalves are affected by multiple threats that vary across the globe; however, pollution and natural system (habitat) modifications being consistently found as the most impacting. Freshwater bivalves are among the most threatened groups in the world with 40% of the species being near threatened, threatened or extinct, and among them the order Unionida is the most endangered. We suggest that global cooperation between scientists, managers, politicians and general public, and application of new technologies (new generation sequencing and remote sensing, among others) will strengthen the quality of studies on the natural history and conservation of freshwater bivalves. Finally, we introduce the articles published in this special issue of Hydrobiologia under the scope of the Second International Meeting on Biology and Conservation of Freshwater Bivalves held in 2015 in Buffalo, New York, USA.This work was supported by FCT—Foundation for Science and Technology, Project 3599—Promote the Scientific Production and Technological Development and Thematic 3599-PPCDT by FEDER as part of the project FRESHCO: multiple implications of invasive species on Freshwater Mussel co-extinction processes (Contract: PTDC/AGRFOR/1627/2014). FCT also supported MLL under Grant (SFRH/BD/115728/2016)

Figure 5 in Barbronia borealis sp. nov., the first salifid leech discovered in Russia, with a global checklist of this genus

Figure 5. External morphological features of the holotype of Barbronia borealis sp. nov. (RMBH Hir_0405). (a-b) Arrangement of three pairs of eyespots: dorsal view (a) and lateral view from right side (b). (c) Ventral region of clitellum, with male (mg) and female (fg) gonopores, and male and female accessory copulatory pores (map and fap, respectively). Body somites are indicated by roman numerals; symbols b1, b2, a2, b5, c11, and c12 indicate the number of annulus. Scale bars = 0.5 mm (a-b) and 1.0 mm (c). Photos: Tatyana A. Eliseeva; graphics: Ivan N. Bolotov.Published as part of <i>Bolotov, Ivan N., Eliseeva, Tatyana A., Kondakov, Alexander V., Gofarov, Mikhail Y., Aksenova, Olga V., Bespalaya, Yulia V., Kropotin, Alexander V., Travina, Oksana V. & Vinarski, Maxim V., 2023, Barbronia borealis sp. nov., the first salifid leech discovered in Russia, with a global checklist of this genus, pp. 24-38 in Ecologica Montenegrina 63</i> on page 32, DOI: 10.37828/em.2023.63.3, <a href="http://zenodo.org/record/8082901">http://zenodo.org/record/8082901</a&gt

Host Range and Phylogenetic Position of Acipenserobdella volgensis (Zykoff, 1904) (Hirudinea: Piscicolidae) with a Global Checklist of Bivalve-Associated Fish Leeches

The fish leech Acipenserobdella volgensis (Hirudinea: Piscicolidae) is a rare and poorly known freshwater species, which is thought to be an obligate parasite of sturgeons. This leech has a disjunctive range in Europe and Eastern Siberia. Here, we estimate the phylogenetic affinities and host range of A. volgensis using a set of DNA sequences (COI and 18S rRNA gene fragments), field observation data, and a review of the body of literature. Based on a time-calibrated Bayesian phylogeny, we show that the European and Siberian lineages of A. volgensis have been separated since the latest Pliocene (mean age = 2.7 Ma). The analysis of available host records indicates that this leech is characterized by a broader host range as it was collected from fish belonging to four families (Acipenseridae, Cyprinidae, Salmonidae, and Esocidae). Conversely, only a few suitable primary hosts (six sturgeons, one cyprinid, and one salmonid fish) were confirmed by earlier research. Moreover, this leech could be considered a facultative mussel-associated species that uses bivalves (duck mussel Anodonta anatina; Unionidae) as shelter. Globally, three other piscicolid leeches have been recorded from the mantle cavity of bivalve molluscs, that is, the freshwater taxa Caspiobdella fadejewi and Alexandrobdella makhrovi, and the marine species Austrobdella coliumicus

Barbronia borealis sp. nov., the first salifid leech discovered in Russia, with a global checklist of this genus

Bolotov, Ivan N., Eliseeva, Tatyana A., Kondakov, Alexander V., Gofarov, Mikhail Y., Aksenova, Olga V., Bespalaya, Yulia V., Kropotin, Alexander V., Travina, Oksana V., Vinarski, Maxim V. (2023): Barbronia borealis sp. nov., the first salifid leech discovered in Russia, with a global checklist of this genus. Ecologica Montenegrina 63: 24-38, DOI: 10.37828/em.2023.63.3, URL: http://dx.doi.org/10.37828/em.2023.63.

<i>Ladislavella tumrokensis</i>: The first molecular evidence of a Nearctic clade of lymnaeid snails inhabiting Eurasia

<p>In this study, we provide the first molecular evidence for a possible connection between freshwater mollusc faunas across the Bering Strait via the Beringian Land Bridge using data inferred from gastropods of the family Lymnaeidae. The gastropods collected from geothermal springs in the Tumrok Mountains, West Kamchatka, Russia, share the nuclear internal transcribed spacer 2 (ITS2) and the cytochrome oxidase subunit I gene (COI) haplotypes, thus being as sister to those recorded for lymnaeid snails in the <i>Stagnicola elodes</i> group from Canada and the USA. Two lymnaeid species, <i>Lymnaea</i> (<i>Orientogalba</i>) <i>tumrokensis</i> Kruglov and Starobogatov, <a href="#cit0033" target="_blank">1985</a> and <i>Lymnaea</i> (<i>Polyrhytis</i>) <i>kurenkovi</i> Kruglov and Starobogatov, <a href="#cit0034" target="_blank">1989</a>, were described from the Tumrok geothermal locality, but actually they are morphological variations of a single taxon of subspecies rank re-classified here as <i>Ladislavella catascopium tumrokensis</i>. This subspecies is the first discovered representative in the genus, which formed a dwarf race in a geothermal habitat. Our findings highlight the possible exchange between freshwater faunas in Beringia during the Pleistocene and an important role of geothermal ecosystems as possible cryptic refugia for freshwater hydrobionts.</p

Figure 1 in Barbronia borealis sp. nov., the first salifid leech discovered in Russia, with a global checklist of this genus

Figure 1. The northernmost occurrences of the Salifidae in their native range in East Asia. The red star indicates the type locality of Barbronia borealis sp. nov. in Primorye Region, Russia. The yellow circles indicate records of Barbronia cf. weberi in Northeastern China (Moore 1930; Yang 1996). The blue circle indicates records of Barbronia gwalagwalensis and B. sp. 'Korea' in South Korea (Kwak et al. 2021). Georeferenced occurrence dataset is presented in Appendix 2 (numbers of localities on the map correspond to those in the appendix).Published as part of &lt;i&gt;Bolotov, Ivan N., Eliseeva, Tatyana A., Kondakov, Alexander V., Gofarov, Mikhail Y., Aksenova, Olga V., Bespalaya, Yulia V., Kropotin, Alexander V., Travina, Oksana V. &amp; Vinarski, Maxim V., 2023, Barbronia borealis sp. nov., the first salifid leech discovered in Russia, with a global checklist of this genus, pp. 24-38 in Ecologica Montenegrina 63&lt;/i&gt; on page 26, DOI: 10.37828/em.2023.63.3, &lt;a href="http://zenodo.org/record/8082901"&gt;http://zenodo.org/record/8082901&lt;/a&gt

Figure 4 in Barbronia borealis sp. nov., the first salifid leech discovered in Russia, with a global checklist of this genus

Figure 4. Dorsal (D) and ventral (V) views of the holotype of Barbronia borealis sp. nov. (RMBH Hir_0405). Abbreviations: PI, prey item (an oligochaete specimen); AS, anterior sucker; PS, posterior sucker; map, male accessory pore; fap, female accessory pore; mg, male gonopore; fg, female gonopore; an, anus. Scale bar = 1.0 mm. Photos: Tatyana A. Eliseeva.Published as part of Bolotov, Ivan N., Eliseeva, Tatyana A., Kondakov, Alexander V., Gofarov, Mikhail Y., Aksenova, Olga V., Bespalaya, Yulia V., Kropotin, Alexander V., Travina, Oksana V. & Vinarski, Maxim V., 2023, Barbronia borealis sp. nov., the first salifid leech discovered in Russia, with a global checklist of this genus, pp. 24-38 in Ecologica Montenegrina 63 on page 31, DOI: 10.37828/em.2023.63.3, http://zenodo.org/record/808290

New Molecular-Based Phylogeny of Mussel-Associated Mites Reveals a New Subgenus and Three New Species Representing an Example of a Host-Driven Radiation in Indochina and Confirms the Concept of Division of the Genus Unionicola Haldeman, 1842 (Acari: Unionicolidae) into Numerous Subgenera

Here we describe a new subgenus and three new species of parasitic water mites in the genus Unionicola (Acari: Hydrachnidia) from Myanmar: Myanmaratax&nbsp;subgen. nov., Unionicola (Myanmaratax) savadiensis&nbsp;subgen. and sp. nov. (hosts: Lamellidens savadiensis and L. generosus), U. (My.) generosa&nbsp;sp. nov. (the same hosts), and U. (My.) trapezidenssp. nov. (hosts: Trapezidens dolichorhynchus and T. angustior). These taxa were identified based on a two-gene phylogenetic analysis (COI + 28S), which also confirms the division of the genus Unionicola into numerous subgenera. The new species are cryptic species, which are morphologically indistinguishable but strongly resemble U. (Prasadatax) brandti Vidrine, 1985 described from Thailand (hosts: Lens spp. and Ensidens spp.). We also transfer the latter taxon from Prasadatax to Myanmaratax based on a set of morphological evidence and propose U. (My.) brandti&nbsp;comb. nov. The new subgenus contains a total of five species, one of which needs future sampling efforts and will be described elsewhere. Additionally, 56 valid subgenera, which were placed in the synonymy of the genus and in one case raised to the genus level, are restored here until robust phylogenetic evidence on their taxonomic status is available. Our results also confirm that Unionicola mites are narrow host specialists that are associated with either one or a few closely related freshwater mussel species belonging to one or two sister genera

Taxonomy and Melanism Patterns of Freshwater Leeches in the Genus <i>Glossiphonia</i> (Hirudinea: Glossiphoniidae) from Northeast Asia

Freshwater leeches belonging to the genus Glossiphonia Johnson, 1816 are fairly common benthic annelids in freshwater ecosystems throughout Eurasia, but the taxonomy of this group remains poorly resolved, and the species content of some local faunas is unsatisfactorily known. For example, it was thought that the only widespread species, Glossiphonia complanata (Linnaeus, 1758), dwells in Northeast Asia. Here, we revise the Northeast Asian Glossiphonia leeches with an integrative taxonomic approach. This revision is based on the largest DNA-sequence and morphological datasets collected to date. Two Glossiphonia species are recorded from the region. First, Glossiphonia koreaensissp. nov., a putative regional endemic species, was discovered in South Korea. Second, a valid name and complete description are provided for Glossiphonia mollissima Moore, 1898 (non-Grube, 1871). The latter name was wrongly applied through misidentification and, according to ICZN (Article 49), is unavailable. Hence, we propose a new name, Glossiphonia mooreisp. nov., in memory of Dr. J. Percy Moore, who discovered this leech. It is a prospective trans-Beringian species, ranging through Eastern Siberia, the Russian Far East, and Alaska (although Alaskan records are based on nonsequenced samples), showing a significant proportion of melanic individuals in samples north of the Arctic Circle. The latter pattern may reflect substrate-induced cryptic coloration (camouflage), but this hypothesis needs to be statistically checked in the future. Finally, a complete checklist of Glossiphonia species is presented