Captive breeding of European freshwater mussels as aconservation tool: A review

1. Freshwater mussels are declining throughout their range. Their importantecological functions along with insufficient levels of natural recruitment haveprompted captive breeding for population augmentation and questions about the usefulness and applicability of such measures. 2. This article reviews the current state of captive breeding and rearing programmes for freshwater mussels in Europe. It considers the various species, strategies, andtechniques of propagation, as well as the different levels of effort requiredaccording to rearing method, highlighting the key factors of success. 3. Within the last 30 years, 46 breeding activities in 16 European countries have been reported, mainly of Margaritifera margaritifera and Unio crassus. Some facilities propagate species that are in a very critical situation, such as Pseudunio auricularius, Unio mancus, and Unio ravoisieri, or multiple species concurrently. Insome streams, the number of released captive-bred mussels already exceeds the size of the remaining natural population. 4. Rearing efforts range from highly intensive laboratory incubation to lowerintensity methods using in-river mussel cages or silos. Most breeding efforts are funded by national and EU LIFE(+) grants, are well documented, and consider the genetic integrity of the propagated mussels. Limited long-term funding perspectives, the availability of experienced staff, water quality, and feeding/survival during early life stages are seen as the most important challenges. 5. Successful captive breeding programmes need to be combined with restoration ofthe habitats into which the mussels are released. This work will benefit from anevidence-based approach, knowledge exchange among facilities, and an overall breeding strategy comprising multiple countries and conservation units. aquaculture, captive breeding, conservation translocation, freshwater mussel culturing, Margaritifera margaritifera, propagation, reintroduction, Unio crassusCaptive breeding of European freshwater mussels as aconservation tool: A reviewpublishedVersio

Influence of parasitism on bioturbation: from host to ecosystem functioning

International audienceBioturbating species represent a typical example of ecosystem engineer species in marine benthic environments. These abundant endo- or epibenthic organisms modify the physical structure and geochemical properties of sediments and, at broader ecosystem scales, impact nutrient flows and benthic community structure. The ecological importance of bioturbators depends on (1) their abundance and (2) the magnitude of their bioturbation activity. We suggest that parasitism has a substantial impact on bioturbators, with cascading effects on their role in ecosystem functioning. Reviewing 5940 papers concerning bioturbation and using a set of selective criteria, we identified 176 bioturbating species, with 31% of these potentially parasitized (micro- and macroparasites). However, there are significant discrepancies in the research effort on parasites among bioturbating groups, the highest effort being devoted to molluscs, whereas studies on annelids and arthropods are rare. Furthermore, studies addressing the impacts of parasites on their bioturbating hosts are still scarce, but evidence we do have indicates that parasites impair their hosts’ physiological state, fecundity, behaviour and survival. Because of impacts of parasites on phenotypic traits related to the bioturbation engineering activity of their hosts, parasitism could play a key role on ecosystem functioning through cascade effects. Yet, studies assessing the intricate link between parasites and their hosts’ bioturbation activity, including potential effects on ecosystem functioning, are very scarce

Sensitivity to cadmium of the endangered freshwater pearl mussel Margaritifera margaritifera from the Dronne River (France): experimental exposure

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How does the bopyrid isopod Gyge branchialis interfere with trace metal bioaccumulation in the mud shrimp Upogebia cf. pusilla?

International audienceParasites are widespread in natural environments, and their impacts on the fitness of their host and, at a broader scale, on ecosystem functioning are well recognized. Over the last two decades, there has been an increasing interest in the effects of parasites in conjunction with other stressors, especially pollutants, on the health of organisms. For instance, parasites can interfere with the bioaccumulation process of contaminants in their host leading to parasitized organisms exhibiting lower pollutants burdens than unparasitized individuals for example. However, the mechanisms underlying these patterns are not well understood. This study examined how the bopyrid parasite Gyge branchialis could lower the cadmium (Cd) uptake of its mud shrimp host Upogebia cf. pusilla. When exposed to water-borne Cd, parasites were able to bioaccumulate this trace metal. However, the uptake of Cd by the parasite was low and cannot entirely explain the deficit of Cd contamination of the host. The weight of gills of parasitized organisms was significantly reduced compared with unparasitized organisms. We suggest that by reducing the surface for metal uptake, parasites could lower the contaminant burden of their host

Locomotion behavior of juveniles of the freshwater pearl mussel Margaritifera margaritifera: A new non-invasive tool for the evaluation of stress effects

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Influence of the parasite worm Polydora sp. on the behaviour of the oyster Crassostrea gigas: a study of the respiratory impact and associated oxidative stress

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Acute Toxicity of Sodium Chloride, Nitrates, Ortho-Phosphates, Cadmium, Arsenic and Aluminum for Juveniles of the Freshwater Pearl Mussel: Margaritifera Margaritifera (L.1758)

International audienceThe freshwater pearl mussel (FWPM) Margaritifera margaritifera (L.1758) is critically endangered in Europe and ecotoxicological studies on the species are scares. Here, 96 h acute toxicity tests were conducted at 16 °C with sodium chloride (NaCl), nitrates (NO3−), ortho-phosphates (PO43−), cadmium (Cd), aluminum (Al) and arsenic (As) on 13- to 28-month-old post-parasitic juveniles. The experimental protocol was developed according to conditions described in a standard guide and was modified in order to assess toxicity thresholds for the Dronne River. Results showed that juveniles were tolerant to concentrations of Al, Cd, As, PO43−, NO3− and NaCl, largely higher than those found in the Dronne river, since 96 h EC50s (effective concentrations) were >954 µg/L for Al; >110 µg/L for Cd; >127 µg/L for As; >5.01 mg/L for PO43−; between 1000 and 1500 mg/L for NO3− and were 1.19 and 1.33 g/L for NaCl. Moreover, the use of a substrate in experiments was found not to affect juvenile responses and younger juveniles seemed more sensitive than older individuals. This study thus provides new data about the tolerance of FWPM to environmental pollution and suggests that pollutant concentrations in the river are significantly lower than levels affecting them

Seasonal influence of parasitism on contamination patterns of the mud shrimp Upogebia cf. pusilla in an area of low pollution

Very few studies have characterized the concentrations of pollutants in bioturbating species. These species are considered as ecosystem engineers and characterizing stressors, such as contaminants, that impact them could lead to a better understanding of the functioning of ecosystems. In addition to contaminants, bioturbators are affected by a wide range of stressors, which can influence their physiological status and their ability to accumulate pollutants. Among these stressors, parasitism is of particular concern due to the ubiquity of parasites in natural environments and their influence on the fitness of their host. This study aims to assess the relationship between parasitism and metal accumulation in the bioturbating mud shrimp Upogebia cf. pusilla. A one-year seasonal survey was conducted in Arcachon Bay, France, with the aims of (1) characterizing the levels of metals in the mud shrimp and (2) evaluating the influence of two macroparasites (a bopyrid isopod and a trematode) on the variation of the metal content in mud shrimp. The bopyrid parasite castrates its female host and a particular attention has therefore been paid to the reproductive cycle of female mud shrimp by quantifying the expression of the vitellogenin gene that encodes the major yolk protein in female crustaceans. The levels of contaminants in mud shrimp appeared low compared to those reported in other crustaceans in areas of higher pollution. Even at these low contamination levels, we observed a significant impact by the bopyrid parasite that depends on season: bopyrid-infested organisms are generally more contaminated than their uninfested conspecifics except in summer when the opposite trend was observed. We suggest that the bopyrid indirectly interferes with the metal accumulation process by altering the reproductive capabilities of the mud shrimp. On the opposite, very low influence of the trematode parasite on the metal content of the host was found

Sensitivity of newly transformed juveniles of the freshwater pearl mussel: Margaritifera margaritifera to acute toxicity of a wide range of contaminants

The freshwater pearl mussel (FWPM) Margaritifera margaritifera is a bivalve mollusk critically endangered in Europe. There is a special concern about the conservation of this species, but little is known about its sensitivity to environmental pollution. Here, acute toxicity tests were conducted at 16°C according to a standard guide for conducting toxicity tests on freshwater mussels (ASTM international E2455), in order to assess toxicity thresholds for arsenic (As), aluminum (Al), cadmium (Cd), copper (Cu), nickel (Ni), nitrates (NO3−), and orthophosphates (PO43−) on newly transformed juveniles of M. margaritifera. The comparison with toxicity data for other newly transformed freshwater mussel juveniles from the same family and superfamily, Margaritiferidae and Unionidae, showed that FWPM juveniles were the most sensitive species to NO3−, among the most sensitive species to Ni, the least sensitive species to Cd, and showed an intermediate sensitivity to Cu compared to other freshwater mussels. This study is the first to provide toxicity thresholds for several pollutants on newly transformed juveniles of the FWPM. This brings new knowledge on its sensitivity to environmental pollution that could be helpful data for conservation strategies and these findings represent the first window for further complex studies