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Integrative phylogenetic, phylogeographic and morphological characterisation of the Unio crassus species complex reveals cryptic diversity with important conservation implications
Distribution, scale, and drivers of mass mortality events in Europe's freshwater bivalves
Abstract Mass mortality events (MMEs) are decimating populations and compromising key ecosystem functions around the globe. One taxon particularly vulnerable to MMEs is freshwater bivalve mollusks. This group has important ecosystem engineering capacities and includes highly threatened and highly invasive taxa. Thus, MMEs of freshwater bivalves have important implications for conservation and ecosystems. Despite this, little is known about the magnitude, frequency, duration, distribution, and causes of freshwater bivalve MMEs. Using a questionnaire, we compiled data from 239 reports describing freshwater bivalve MMEs across 22 European countries since 1960. With these data, we analyzed trends in MME timing, location, and magnitude; identified the species affected; and evaluated the suggested causes (including reporter certainty). We found that the frequency of reports of MMEs increased each year, MMEs affected a broad range of species, clear geographical patterns linking certain causes to specific locations were lacking, factors related to drying and habitat destruction predominated suggested causes, and considerable uncertainty surrounded the causes of many MMEs, particularly those associated with potential pollutants and disease agents. Based on our findings, we recommend the standardization of many aspects of MME research (e.g., reporting and recovery assessment protocols), increased surveying for MMEs, further investigation into the causes of MMEs, especially those with significant uncertainty, and immediate actions to improve waterbody management, mitigate the effects of high temperatures, and further protect freshwater bivalves through the development and implementation of appropriate management actions and legislation.
Lower parasite pressure in invasive freshwater bivalves than in sympatric native Unionidae mussels in southern European lakes
AbstractThe Enemy Release Hypothesis (ERH) proposes that the success of bioinvasions is attributable to lower enemy pressure on invasive species compared to native ones, giving a competitive advantage for invaders. In line with the hypothesis, we previously observed in northern European bodies of fresh water that invasive bivalves were subject to lower parasite pressure than sympatric native mussels. Here, we investigated ERH in three southern European lakes, where the native mussels are rapidly declining and being replaced by non-native bivalves. In total, 679 bivalves (n of individuals per species per lake varying from 12 to 187) were collected during 2016â2018. Ten parasite taxa were found. The mean lake-specific number of parasite taxa in the native mussels (Anodonta exulcerata, A. cygnea, A. anatina and Unio elongatulus) was 2.6 times that in the invasive bivalves (Dreissena polymorpha, Corbicula fluminea and Sinanodonta woodiana). Similarly, the mean lake-specific sum of prevalences of infection by different parasite taxa in the native mussels was 3.4 times that in the invasive bivalves. Notable was the complete lack of parasites in C. fluminea. Thus, the results supported the Enemy Release Hypothesis and were in accordance with previous results from northern Europe, suggesting, on average, a lower parasite pressure in invasive bivalves than in sympatric native mussels. As parasites are usually harmful, this may contribute to the observed successful invasion of non-native freshwater bivalves in Europe.
Review of the globally invasive freshwater mussels in the genus Sinanodonta Modell, 1945
AbstractIn this review, we synthesize the current knowledge of the biology, ecology, and impact of Sinanodonta freshwater mussels (Bivalvia, Unionidae), native to East Asia, that have successfully invaded Europe, Central America, North Africa, and several Asian regions. The main introduction pathways of Sinanodonta were reconstructed based on DNA sequence data and distribution records. We show that invasive lineages of Sinanodonta belong to three species, namely, S. woodiana s. str. (âtemperate invasiveâ lineage), S. pacifica (âtropical invasiveâ lineage), and S. lauta. Their generalist fish-dispersed larvae, short life span, high fecundity, use by humans for multiple purposes, and ability to establish populations in anthropogenically disturbed conditions were identified as crucial traits driving their invasions. Information on the consequences is scarcer, but Sinanodonta can impact native species through larval parasitism, host fish/food competition, and parasite transmission. In addition, ecosystem effects through their filtrationâbiodepositionâexcretion activity and the occurrence of massive die-offs were detected. Ecosystem services and disservices have not yet been quantified, even at local scales, and management methods in the invasive range are understudied. A better understanding of Sinanodonta ecology, impacts, and management options is urgently needed to make informed decisions and set realistic and impactful restoration goals.
Off the conservation radar: the hidden story of Europe's tiny pea clams (Bivalvia: Sphaeriidae)
AbstractThis study highlights the conservation problems faced by the tiny freshwater bivalves of the family Sphaeriidae, also known as pea, pill, or fingernail clams (or mussels) in Europe. Despite their global distribution, assumed ecological importance, and potential uses, basic knowledge about their taxonomy, biology, and ecology is very limited and much lower than for the larger freshwater bivalve taxa. Immediate scientific priorities are required to fill knowledge gaps regarding their taxonomy, genetic diversity, distribution, reproductive cycle, ecosystem functions, and population trends. Such fundamental knowledge is necessary to identify specific threats and develop appropriate conservation actions. Deploying environmental DNA analysis at a large scale could be a valuable way to fill gaps in distribution and strengthen monitoring in areas where local taxonomic knowledge is lacking. Until taxon-specific management plans can be developed, we recommend that efforts concentrate on the general protection and restoration of wetland habitats, implementing pollution control measures, and managing invasive species. These actions should be complemented by community engagement through citizen science initiatives. Additionally, prioritising data collection to fill existing knowledge gaps and updating conservation statuses (Red Lists) based on comprehensive assessments will be crucial. Implementing these actions will provide a starting point for the broader protection of freshwater ecosystems, thus benefiting pea clams and other interconnected species within these habitats.
Species composition in assemblages of the family Unionidae Rafinesque, 1820 (Mollusca: Bivalvia) as an indicator of ecological changes in water bodies of Central Polissia, Ukraine
Though Ukraine is one of the countries with insufficient water supply, the northern region of central Polissia has a dense river network. The regionâs major rivers â Teteriv, Sluch, Ubort, and Uzh â have undergone significant anthropogenic change. Water pollution has adversely affected their fauna, including the Unionidae (Mollusca: Bivalvia). This study has monitored these changes, and was conducted in two stages. A total of 78 sites with habitats typical for the Unionidae were examined; 45 in 1998â2013, of which 24 were resampled in 2019â2020, and a further 33 were sampled at the same time. Six native species generally characteristic of Ukraine (Unio pictorum Linnaeus, 1758, U. tumidus Philipson, 1788, U. crassus Philipsson, 1788, Anodonta anatina Linnaeus, 1758, A. cygnea Linnaeus, 1758, and Pseudanodonta complanata Rossmassler, 1835) were recorded. While nearly all sites examined in 1998â2013 held some unionids, by 2019â2020, they were recorded in only 62.5% out of the total number of sites in Sluch River basin, 80% in Teteriv River, 40% in Ubort River, and 62.5% in Uzh River. The species richness at sites where unionids were recorded had also declined. Pseudanodonta complanata, recorded in every surveyed basin in 1998â2013, was not observed at any of the sites examined in 2019â2020. In 23 out of the 24 re-examined sites, the extinction of one or more Unionidae species was recorded. It is evident that the role of these large mussels as ecosystem engineers is being compromised.
A global metaâanalysis of ecological functions and regulating ecosystem services of freshwater bivalves
AbstractFreshwater bivalves are globally distributed, diverse, and common in benthic communities. Many taxa, particularly in the most speciesârich order, Unionida, are declining due to anthropogenic stressors, while a small number of nonânative species have become increasingly abundant and widespread, commonly replacing native bivalve assemblages. To understand how these global changes may impact ecosystems and people, we conducted a metaâanalysis of existing literature quantifying the ecological functions (=âsupporting or intermediate ecosystem services) and regulating ecosystem services of freshwater bivalves (hereafter âecosystem servicesâ). Random effects metaâanalysis modeling across 447 case studies revealed a positive effect on human health, safety, or comfort of freshwater bivalve ecosystem services overall and specifically, via effects on native macrofauna, microorganisms, wastes, and pollutants, and the physicoâchemical condition or quantity of sediments. Generally, effects of native species and species within the orders Unionida and Venerida were more significant and positive than those of other freshwater bivalves. No significant overall effect was found for ecosystem services related to zooplankton, algae, invasive species, and the physicoâchemical condition of ambient water. Moreover, a significant bias toward publication of positive results existed for studies quantifying ecosystem services related to algae. These findings illustrate the global importance of the ecosystem services of freshwater bivalves and highlight the need for largeâscale conservation and restoration efforts for their species and populations globally, including those of common species. Our findings also question common assumptions of strong and ubiquitous effects of freshwater bivalves on algae and water condition, cautioning against extrapolating observations across systems.
A roadmap for the conservation of freshwater mussels in Europe
AbstractEurope has a long history of human pressure on freshwater ecosystems. As pressure continues to grow and new threats emerge, there is an urgent need for conservation of freshwater biodiversity and its ecosystem services. However, whilst some taxonomic groups, mainly vertebrates, have received a disproportionate amount of attention and funds, other groups remain largely off the public and scientific radar. Freshwater mussels (Bivalvia, Unionida) are an alarming example of this conservation bias and here we point out six conceptual areas that need immediate and longâterm attention: knowledge, threats, socioeconomics, conservation, governance and education. The proposed roadmap aims to advance research, policy and education by identifying the most pressing priorities for the shortâ and longâterm conservation of freshwater mussels across Europe.
Enemy release: loss of parasites in invasive freshwater bivalves Sinanodonta woodiana and Corbicula fluminea
Invasive freshwater bivalves harm native species, ecosystems and biodiversity, and incur economic costs. The enemy release hypothesis posits that invasive species are released from enemies during the invasion process, giving them a competitive advantage in the new environment. We compared parasitism in two invasive freshwater bivalves, Sinanodonta woodiana and Corbicula fluminea between their original range (China) and invaded range (Europe). For S. woodiana , the average sampleâsizeâstandardized populationâspecific parasite taxon richness was 2.1 times as high, and sum of prevalence was 3.0 times as high in the native range (3 populations, 81 individuals studied) as in the invaded range (6 populations, 210 individuals studied). For C. fluminea , the average standardized populationâspecific parasite taxon richness was 1.3 and sum of prevalences was 27.5 in the native range (4 populations, 749 individuals studied), whereas all European C. fluminea were free of parasites (7 populations, 418 individuals studied). The results demonstrate loss of parasites as a result of invasion. Previous studies have shown that parasite pressure on S. woodiana and C. fluminea in the invaded range in Europe is, on average, lower than on sympatric native freshwater mussel populations. Together, these results support one aspect of the enemy release hypothesis: invasive bivalves experience reduced parasite loads as a result of invasion, which may contribute to their success, given the costs typically imposed by parasitism.
Pro-ecological and conservation activities are not always beneficial to nature: a case study of two lowland streams in Central Europe
AbstractSince 1990 and in particular, after the implementation of the Water Frame Directive, many positive effects of pro-ecological projects are evident; unfortunately, examples of adverse effects have also been observed. This study aims to indicate how some ill-considered actions, called âpro-ecologicalâ, may lead to habitat degradation and the disappearance of valuable hydrobiont species. Two watercourses, representing the lowland gravel stream and sandy stream type, were selected for the study. Literature indicated that in the past, these watercourses were characterized by an excellent ecological status and the presence of valuable rheophilic fauna and flora. Environmental parameters were recorded, macroinvertebrates and ichthyofauna were sampled and analyzed, and finally, indexes were calculated. The results were compared with literature data. In the course of studies conducted in 2011â2015, drastic habitat deterioration and extensive changes in the species structure of ichthyofauna and aquatic invertebrates were observed. Changes in the Smolnica stream have been caused by the three retention basins constructed in 2000, along the lower and middle course; while in Kiszewko, however, the factor for habitat deterioration was connected with the excessive expansion of the Eurasian beaver (Castor fiber), which created a beaver pond 20 m in width, with impoundment elevations of up to 2 m.
Selected Quality Attributes of Freshwater Mussel Powder as a Promising Ingredient for Pet Food
The aim of this study was to describe the quality attributes of a freeze-dried preparation obtained from freshwater mussel Sinanodonta woodiana (SW) soft tissue in respect to its potential as a novel pet food ingredient. After ecotoxicological testing of the raw material with MARA (Microbial Assay for Risk Assessment), the basic physico-chemical properties of the powder, such as approximate composition, bulk density, color parameters, water activity, electrophoretic analysis (SDS-PAGE), solubility, gelling and emulsifying capacity, were analyzed. The powder with a water activity of 0.43 offers a toxically safe preparation that contains over 34% protein/100 g of dry matter (DM). The SDS-PAGE profile showed twelve protein bands with a molecular weight (MW) ranging from >250 to 10 kDa. Taurine content has been estimated at an essential amount above 150 mg/100 g of DM. The powder possessed desirable emulsifying properties with 230 mL per 1 g and demonstrated the ability to form a firmer gel with a strength of 152.9 g at a temperature above 80 °C with at least 10% protein content. The L*, a*, and b* values characterizing powder color were found to be 69.49, 16.33, and 3.86, respectively. The SW mussel powder seems to be a promising ingredient that can be added with other binding or gelling agents in order to improve both the taste and acceptance of the final pet food products.