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Understanding the ecological assembly of parasite communities is critical to characterise how changing host and environmental landscapes will alter infection dynamics and outcomes. However, studies frequently assume that (a) closely related parasite species or those with identical life-history strategies are functionally equivalent, and (b) the same factors will drive infection dynamics for a single parasite across multiple host species, oversimplifying community assembly patterns. Here, we challenge these two assumptions using a naturally occurring host–parasite system, with the mussel Anodonta anatina infected by the digenean trematode Echinoparyphium recurvatum, and the snail Viviparus viviparus infected by both E. recurvatum and Echinostoma sp. By analysing the impact of temporal parasite dispersal, host species and size, and the impact of coinfection (moving from broader environmental factors to within-host dynamics), we show that neither assumption holds true, but at different ecological scales. The assumption that closely related parasites can be functionally grouped is challenged when considering dispersal to the host (i.e. larger scales), while the assumption that the same factors will drive infection dynamics for a single parasite across multiple host species is challenged when considering within-host interspecific competition (i.e. smaller scales). Our results demonstrate that host identity, parasite identity and ecological scale require simultaneous consideration in studies of parasite community composition and transmission. [ABSTRACT FROM AUTHOR]

Biological early warning systems (BEWSs) monitor the behaviour or physiology of living organisms as an indirect mechanism to sense local environmental changes, and have become a widely established tool for monitoring water pollution. Complementary to conventional chemical and physical techniques, their strength lies in the ability to continuously monitor water quality, providing direct and rapid warning of toxic discharges. Bivalve molluscs (mussels and clams) are ideal sensing organisms for BEWSs, owing to their: high water filtration capacity; sensitivity to numerous, diverse pollutants; considerable longevity; high abundance; and wide range of physical responses to environmental change. Two behavioural metrics of bivalves have dominated in ecotoxicological studies, and consequently spawned development into BEWSs: valve movements, typically measured using electromagnetic techniques; and bivalve cardiac activity, typically measured using infrared photoplethysmography. However, other, less studied bivalve behaviours may exhibit pollutant impacts, including shell growth and dissolution, premature egg/larval release, horizontal movement, and burial. Such metrics may, with further research, provide bases for future BEWSs, some through current valve movement monitoring technology, others potentially through acoustic telemetry. Future bivalve-based BEWSs may become more informative and sensitive through the greater nuance that lies in integration of different metrics simultaneously and/or multi-species monitoring. Future directions may seek techniques that reduce disturbance to bivalves and enable observation of a more natural mode of behaviour, through using untethered, or entirely unequipped, specimens. With rigorous controls for individual- and population-level variation, bivalves have great power as biosensors and, bolstered by the scope for future advancements, this field has the potential to make significant contributions to future water quality management. [ABSTRACT FROM AUTHOR]

Plastic debris widely pollutes freshwaters. Abiotic and biotic degradation of plastics releases carbon-based substrates that are available for heterotrophic growth, but little is known about how these novel organic compounds influence microbial metabolism. Here we found leachate from plastic shopping bags was chemically distinct and more bioavailable than natural organic matter from 29 Scandinavian lakes. Consequently, plastic leachate increased bacterial biomass acquisition by 2.29-times when added at an environmentally-relevant concentration to lake surface waters. These results were not solely attributable to the amount of dissolved organic carbon provided by the leachate. Bacterial growth was 1.72-times more efficient with plastic leachate because the added carbon was more accessible than natural organic matter. These effects varied with both the availability of alternate, especially labile, carbon sources and bacterial diversity. Together, our results suggest that plastic pollution may stimulate aquatic food webs and highlight where pollution mitigation strategies could be most effective. Ultra-high resolution mass spectrometry revealed that plastic bags leach labile compounds. Bioassays performed in Scandinavian lakes indicated that these compounds are incorporated into biomass faster and more efficiently than natural organic matter. [ABSTRACT FROM AUTHOR]

The naiads, large freshwater mussels (Unionida), have very long life spans, are large-bodied, and produce thousands to millions of larvae (glochidia) which typically must attach to host fish tissues to metamorphose into a juvenile mussel. Glochidia develop within a female's marsupial gill demibranch, thus their number is restricted by female size. However, larger mussels acquire more energy, which could be invested in either larger-sized glochidia, in a more glochidia, or a combination of both. The high level of host specialization seen in many naiads may constrain glochidial size and shape around a narrow optimum, while naiads that use a wide range of host fishes may be predicted to possess greater plasticity in glochidial morphology. In this paper, we investigated the relationship between maternal body size and progeny body size and shape, aided by modern digital microscopy. We analyzed the between- and within- species variation of glochidia size and shape relative to female size in four widespread species of European naiads: Anodonta anatina, Anodonta cygnea, Unio crassus and Unio tumidus. Whereas the total reproductive output is collinear with female body size, substantial differences between species in glochidia size were found within genus Anodonta, but not genus Unio where glochidial size is remarkably consistent. The glochidial shape, however, differed within both Unio and Anodonta. We interpret this constant within-species glochidial size in Unio as reflecting a constraint imposed by the likelihood of successful transmission onto and off from a narrow range of hosts, whereas their shape seems to be less constrained. The Anodonta species, inhabiting a wide spectrum of habitats and using more than twice the number of fish hosts than Unio spp., have larger glochidia with greater variation in size and shape. Our results suggest that measures of glochidial variability may also serve as an indicator of host specificity in other naiads. [ABSTRACT FROM AUTHOR]

However, these models can only be used for one parasite at a time, and so possible interactions between parasites need to be indirectly estimated by including other parasites as a predictor in separate models for each parasite studied (e.g. Markle et al. [18]; Obiegala et al. [21]). This example is particularly pertinent; while the mobility of parasite life history stages has been demonstrated as important in driving infection dynamics and parasite infracommunity structure in terms of both presence and abundance (e.g. Lhorente et al. [17]; Mazé-Guilmo et al. [19]), the relative mobilities of different hosts, and specifically the mobile-immobile contrast, are an underdeveloped area of research. More generally, we recommend careful consideration of how host and parasite traits as well as the environment affect parasite prevalences and parasite abundances and an acknowledgement that these effects may not be the same. For example, whether parasites are directly transmitted between conspecifics (i.e. microparasites) or environmentally transmitted (i.e. macroparasites) can alter the risk of a parasite infection in the same host population (Han et al. [12]), though whether this extended to parasite intensity was not explored. [Extracted from the article]

The global bivalve shellfish industry makes up 25% of aquaculture, is worth USD $17.2 billion year−1, and relies upon a supply of juvenile bivalves produced by adult broodstock in hatcheries. Today large quantities of live algae are grown to feed broodstock at $220 kg−1, driving highly unsustainable energy and resource use. New advances in algal and microencapsulation technology provide solutions. We developed microencapsulated Schizochytrium algae diets, which can be produced sustainably at < $2 kg−1 from organic side-streams, and are shelf-stable to minimise waste. Physiological, histological, and cutting-edge metabolomic analyses demonstrate that in commercial settings sustainable microencapsulated diets facilitate improved sexual development and 12 × greater omega-3 levels in oysters relative to conventional live algal diets. Every tonne bivalve protein produced instead of fish spares 9 ha, 67 tonnes CO2, and 40,000 L freshwater. Further research into microencapsulated diets could support bivalve industry expansion, and contribute towards a step-change in sustainable global food production through improved aquaculture practices. [ABSTRACT FROM AUTHOR]

Invasive alien species (IAS) are one of the greatest drivers of ecological change. Typically, control uses chemical agents that often are ineffective, harmful to non-target organisms, and environmentally persistent. Bivalves are frequently high impact IAS, but have proven particularly hard to control due to their valve-closing response when exposed to conventional control agents. Microencapsulation of biocides with edible coatings represents a highly targeted delivery route, bypassing avoidance responses and accumulating in bivalves through their prodigious filter feeding. Uneaten microcapsules degrade and become biologically inactive within hours thus reducing potential impacts on non-target biota. We manufactured two new formulations of microcapsules (BioBullets). Particles were designed to mimic natural food particles (algae) in terms of size (9.5 ± 0.5 to 19.4 ± 1.3 SE µm diameter), buoyancy (near neutral) and shape (spherical). Laboratory exposures demonstrated that two formulations effectively controlled the Gulf wedge clam Rangia cuneata, an IAS currently spreading rapidly through Europe. A single dose of 2–6 mg L−1 of the active ingredient in a static system achieved 90% mortality after 30 days of exposure. Microencapsulation offers an effective and targeted management tool for rapid responses following the early detection of both Gulf wedge clams and many other filter-feeding IAS, and may be especially effective in closed systems or where populations remain very localised. [ABSTRACT FROM AUTHOR]

Letter to the Editor [ABSTRACT FROM AUTHOR]

Non-indigenous crayfish often have major ecological impacts on invaded water bodies, and have contributed to the decline of native crayfish species throughout Europe. The American signal crayfish, Pacifastacus leniusculus, is the most widespread invasive crayfish in Great Britain, where the zebra mussel, Dreissena polymorpha, is similarly an invasive pest species. The potential for the American signal crayfish to regulate zebra mussel populations was investigated through a series of laboratory experiments. Crayfish were found to be highly size selective, consuming significantly more of the smallest size class of zebra mussels offered (7-12 mm), over medium (16-21 mm) and large (25-30 mm). Crayfish feeding rate on zebra mussels was not altered when mussels were presented clumped together in natural druses compared with mussels in a disassembled druse. Crayfish spent significantly more time foraging when mussels were unattached, and a greater proportion of attacks were on medium and large than on small mussels (83% of attacks were on medium and large mussels when unattached as opposed to 47% when on druses). Individual crayfish feeding rate decreased significantly at densities of > ~5 crayfish m. Signal crayfish are, therefore, unlikely to be able to significantly impact established populations of zebra mussels in the wild, although zebra mussels have the potential to provide crayfish with a substantial food source. [ABSTRACT FROM AUTHOR]

The European bitterling, Rhodeus amarus, is a non-indigenous fish species in British fresh waters. It lays its eggs in unionid mussels which themselves are vulnerable to fouling by the non-indigenous zebra mussel, Dreissena polymorpha. Observations from an unmanipulated natural system showed that only 27% of zebra mussel-fouled Unio pictorum hosted bitterling, while 47% of unfouled U. pictorum hosted bitterling. We conducted a field experiment in the River Great Ouse catchment, Cambridgeshire, England in May–June 2007 and 2008 to quantify the impact of zebra mussels on bitterling load in host mussels. Zebra mussel-fouled unionids were significantly less likely to host bitterling than unfouled unionids. The number of unionids hosting bitterling did not differ significantly whether the zebra mussels fouling the unionid were alive or dead. Bitterling appeared to discriminate against zebra mussel-fouled unionids less as the 2007 breeding season advanced, potentially because preferred unfouled unionids had a higher bitterling load, and were therefore relatively lower quality hosts than at the start of the breeding season. [ABSTRACT FROM AUTHOR]

This document is a correction to a publication titled "Synopsis of the European Freshwater Mussels: Pseudunio auricularius (Spengler, 1793), the Giant Freshwater Pearl Mussel." The correction states that an incorrect version of Figure 3 was used in the original publication and some white dots in the western part of Spain had to be removed. The correct version of Figure 3 can be found in the correction document. The original article can be accessed online. The correction is authored by Keiko Nakamura, Karl M. Wantzen, Joaquin Soler, Ronaldo Sousa, Karl-Otto Nagel, David C. Aldridge, Manuel Lopes-Lima, and Vincent Prié. [Extracted from the article]

Here, we present a synthesis of the available knowledge on the Giant Freshwater Pearl Mussel Pseudunio auricularius (= Margaritifera auricularia) (Spengler, 1793). We also identify critical knowledge gaps that require attention for effective conservation guidance and species recovery. Pseudunio auricularius is one of Europe’s most endangered invertebrate species, with its range having been reduced by over 90% in the last two centuries. Long thought to be extinct, it was rediscovered in Spain and France in the 1990s–2000s, but these populations are in a very critical situation. Pseudunio auricularius lives in gravelly, stable and well-oxygenated sediments. Larvae (glochidia) attach to fish gills to complete their life cycle. The primary host fish, the Atlantic sturgeon Acipenser sturio, now extinct in European rivers, Salaria fluviatilis in Spain and Petromyzon marinus in France, are threatened. Other stressors are the deterioration of mussel habitats and water quality, climate change and invasive species such as Corbicula spp. The earliest life stages are most vulnerable, further ecological studies are urgently needed. Monitoring and conservation measures such as captive breeding will continue in both countries. Catchment-wide restoration of river morphodynamics and water quality is needed to allow the re-establishment of this emblematic species and its host fishes. [ABSTRACT FROM AUTHOR]