Mussel Physiology Research Articles

The effect of simulated marine heatwaves on green-lipped mussels, Perna canaliculus: A near-natural experimental approach

Marine heatwaves (MHW) are projected for the foreseeable future, affecting aquaculture species, such as the New Zealand green-lipped mussel (Perna canaliculus). Thermal stress alters mussel physiology highlighting the adaptive capacity that allows survival in the face of heatwaves. Within this study, adult mussels were subjected to three different seawater temperature regimes: 1) low (sustained 18 °C), 2) medium MHW (18–24 °C, using a +1 °C per week ramp) and 3) high MHW (18–24 °C, using a +2 °C per week ramp). Sampling was performed over 11 weeks to establish the effects of temperature on P. canaliculus survival, condition, specific immune response parameters, and the haemolymph metabolome. A transient 25.5–26.5 °C exposure resulted in 61 % mortality, with surviving animals showing a metabolic adjustment within aerobic energy production, enabling the activation of molecular defence mechanisms. Utilisation of immune functions were seen within the cytology results where temperature stress affected the percentage of superoxide-positive haemocytes and haemocyte counts. From the metabolomics results an increase in antioxidant metabolites were seen in the high MHW survivors, possibly to counteract molecular damage. In the high MHW exposure group, mussels utilised anaerobic metabolism in conjunction with aerobic metabolism to produce energy, to uphold biological functions and survival. The effect of exposure time was mainly seen on very long-, and long chain fatty acids, with increases observed at weeks seven and eight. These changes were likely due to the membrane storage functions of fatty acids, with decreases at week eleven attributed to energy metabolism functions. This study supports the use of integrated analytical tools to investigate the response of marine organisms to heatwaves. Indeed, specific metabolic pathways and cellular markers are now highlighted for future investigations aimed at targeted measures. This research contributes to a larger program aimed to identify resilient mussel traits and support aquaculture management.

Multiple responses of Mytilus galloprovincialis to plastic microfibers

Plastic microfibers (MF) represent the major source of MF found in the environment, the majority made of polyester (PES). Marine bivalves, suspension feeders widespread in coastal areas subjected to higher anthropogenic input, can accumulate MF from the water column in their tissues. This raised some concern about their possible impact on bivalve health and potential transfer along the food chain. In this work, the effects of PES-MF on the mussel Mytilus galloprovincialis were investigated, utilizing MF obtained by cryo-milling of a fleece cover. Fiber characterization indicated the polymer composition as polyethylene terephthalate (PET); the size distribution was in a length range resembling that of MF released from textile washing, and including those that can be ingested by mussels. MF were first screened for short-term in vitro immune responses in mussel hemocytes. The effects of in vivo exposure (96 h, 10 and 100 μg/L, corresponding to about 150 and 1500 MF/mussel/L, respectively), were then evaluated. Data are presented on hemolymph immune biomarkers (Reactive Oxygen Species and nitric oxide production, lysozyme activity), and on antioxidant biomarkers (catalase and glutathione S-transferase) and histopathology in gills and digestive gland. Tissue MF accumulation was also evaluated.MF exposure stimulated extracellular immune responses both in vitro and in vivo, indicating induction of immune/inflammatory processes. In both tissues, stimulation of antioxidant enzyme activities, suggesting oxidative stress conditions, and histopathological changes were observed, with stronger effects often observed at lower concentration. Although mussel retained a very small fraction of MF, their accumulation was higher in the digestive gland than in gills, and in both tissues of mussels exposed to the lowest concentration. Selective accumulation of shorter MF was also observed, particularly in gills. Overall, the results demonstrate that at environmental exposure levels, PET-MF have a significant impact on mussel physiology, affecting multiple processes in different tissues.

SNP discovery and genetic structure in blue mussel species using low coverage sequencing and a medium density 60 K SNP-array.

Blue mussels from the genus Mytilus are an abundant component of the benthic community, found in the high latitude habitats. These foundation species are relevant to the aquaculture industry, with over 2 million tonnes produced globally each year. Mussels withstand a wide range of environmental conditions and species from the Mytilus edulis complex readily hybridize in regions where their distributions overlap. Significant effort has been made to investigate the consequences of environmental stress on mussel physiology, reproductive isolation, and local adaptation. Yet our understanding on the genomic mechanisms underlying such processes remains limited. In this study, we developed a multi species medium-density 60 K SNP-array including four species of the Mytilus genus. SNPs included in the platform were called from 138 mussels from 23 globally distributed mussel populations, sequenced using a whole-genome low coverage approach. The array contains polymorphic SNPs which capture the genetic diversity present in mussel populations thriving across a gradient of environmental conditions (~59 K SNPs) and a set of published and validated SNPs informative for species identification and for diagnosis of transmissible cancer (610 SNPs). The array will allow the consistent genotyping of individuals, facilitating the investigation of ecological and evolutionary processes in these taxa. The applications of this array extend to shellfish aquaculture, contributing to the optimization of this industry via genomic selection of blue mussels, parentage assignment, inbreeding assessment and traceability. Further applications such as genome wide association studies (GWAS) for key production traits and those related to environmental resilience are especially relevant to safeguard aquaculture production under climate change.

Contaminants of emerging concern in the Maumee River and their effects on freshwater mussel physiology.

Contaminants of emerging concern pose a serious hazard to aquatic wildlife, especially freshwater mussels. The growing number of contaminants in aquatic systems requires scientists and managers to prioritize contaminants that are most likely to elicit a biological response for further monitoring and toxicological testing. The objectives of this study were to identify a sub-category of contaminants most likely to affect Pyganodon grandis and to describe alterations in metabolites and gene expression between various sites. Mussels were deployed in cages for two weeks at four sites along the Maumee River Basin, Ohio, USA. Water samples were analyzed for the presence of 220 contaminants. Hemolymph samples were collected for metabolomics and analyzed using mass spectrometry. Contaminants that significantly covaried with metabolites were identified using partial least-squares (PLS) regression. Tissue samples were collected for transcriptomics, RNA was sequenced using an Illumina HiSeq 2500, and differential expression analysis was performed on assembled transcripts. Of the 220 targeted contaminants, 69 were detected in at least one water sample. Of the 186 metabolites detected in mussel hemolymph, 43 showed significant differences between the four sites. The PLS model identified 44 contaminants that significantly covaried with changes in metabolites. A total of 296 transcripts were differentially expressed between two or more sites, 107 received BLAST hits, and 52 were annotated and assigned to one or more Gene Ontology domains. Our analyses reveal the contaminants that significantly covaried with changes in metabolites and are most likely to negatively impact freshwater mussel health and contribute to ongoing population declines in this group of highly endangered animals. Our integration of "omics" technologies provides a broad and in-depth assessment of the short-term effects of contaminants on organismal physiology. Our findings highlight which contaminants are most likely to be causing these changes and should be prioritized for more extensive toxicological testing.

Bioplastic leachates characterization and impacts on early larval stages and adult mussel cellular, biochemical and physiological responses

Bioplastics are promoted as safer alternatives to tackle the long-term persistence of conventional plastics. However, information on the potential release of additives and non-intentionally added substances (NIAS) in the surrounding environment is limited, and biological effects of the leachates have been little studied. Leachates produced from three bioplastics, i.e. compostable bags (CB), bio-polyethylene terephthalate bottles (bioPET) and polylactic acid cups (PLA), and a control polymeric material, i.e. rubber tire (TR), were examined. The chemical nature of bioplastic polyesters PET, PLA and poly (butylene adipate-co-terephthalate) (PBAT) in CB, was confirmed by analytical pyrolysis. Fragments were incubated in artificial sea water for 14 days at 20 °C in darkness and leachate contents examined by GC-MS and HPLC-MS/MS. Catalysts and stabilizers represented the majority of chemicals in TR, while NIAS (e.g. 1,6-dioxacyclododecane-7,12-dione) were the main components of CB. Bisphenol A occurred in all leachates at a concentration range 0.3–4.8 μg/L. Trace metals at concentrations higher than control water were found in all leachates, albeit more represented in leachates from CB and TR. A dose response to 11 dilutions of leachates (in the range 0.6–100%) was tested for biological effects on early embryo stages of Mytilus galloprovincialis. Embryotoxicity was observed in the whole range of tested concentrations, the magnitude of effect depending on the polymers. The highest concentrations caused reduction of egg fertilization (CB, bioPET, TR) and of larvae motility (CB, PLA, TR). TR leachates also provoked larvae mortality in the range 10–100%. Effects on adult mussel physiology were evaluated after a 7-day in vivo exposure to the different leachates at 0.6% concentration. Nine biomarkers concerning lysosomal functionality, neurotransmission, antioxidant and immune responses were assessed. All lysosomal parameters were affected, and serum lysozyme activity inhibited. Harmonized chemical and biological approaches are recommended to assess bioplastic safety and support production of sustainable bioplastics.

Effect of culture depth on the shell thickness of the blue mussel Mytilus edulis: a practical case study comparing direct and indirect methods of measurement

ABSTRACT Mytilus species have a fundamental role in coastal environments and constitute an important aquaculture resource. Their shell has a protective function and is affected by multiple factors, such as the size of the animal, density, environmental characteristics and presence of predators. It is crucial to accurately estimate shell thickness in order to understand the effects of the ever-changing environment on mussel physiology, morphology and ecology. This study compares a newly developed direct method for measuring shell thickness, using scanning electron microscopy (SEM), and a widely used indirect method (shell thickness index, STI), in the context of a practical case study of the blue mussel Mytilus edulis. In this study, STI did not appear as highly correlated to direct thickness measurement as in previous studies. This study also showed a weaker relationship between measured shell length and STI. In the case study, assessing the effect of culture depth on M. edulis growth and condition, STI showed a significant variation with depth, while SEM measured thickness did not. Therefore, the choice to use STI vs direct measurement of shell thickness drastically changed the results and interpretation of the case study. This work highlights the importance of a carefully designed method for measuring shell thickness and emphasizes that, before application, indirect methods should be quality controlled for the population studied. However, when high precision is needed for shell thickness measurements the application of SEM-based techniques may be necessary. This is the first study where SEM-based techniques have been used to measure shell thickness in M. edulis.

Molecular and biochemical effects on metabolism and immunity of Hyriopsis cumingii fed with four different microalgae

Hyriopsis cumingii has attracted attention because of its pearl production performance and water purification capacity. Realizing sustainable industrialized culture of H. cumingii or applying it to bivalve biomanipulation for controlling water eutrophication needs urgent studies about the selection of suitable algae and the effects of different microalgae on mussel physiology. To contrast molecular and biochemical effects of high-quality microalgal diets (Chlorella vulgaris, Navicula pelliculosa, and Cyclotella sp.) with toxic Microcystis aeruginosa on metabolism and immune physiology of H. cumingii, levels of related enzymes and genes were analyzed during the 28-day exposure period. Results showed that the Cyclotella sp. diet could significantly (p < 0.05) maintain higher levels of metabolic enzymes (glutamic oxaloacetate transaminase (GOT), glutamic pyruvate transaminase (GPT), pyruvate kinase (PK), and hexokinase (HK)) and genes (CPT1 and LDLR). C. vulgaris and N. pelliculosa treatments significantly (p < 0.05) reduced activities of these metabolic parameters. The M. aeruginosa treatment significantly (p < 0.05) enhanced levels of immune enzymes (alkaline phosphatase (AKP), superoxide dismutase (SOD), and catalase (CAT)) and genes (HcIL-17 and IAP) on day 1 or 7, and there was a significant (p < 0.05) reduction on day 28. Results suggested that Cyclotella sp. was the suitable algae for H. cumingii, followed by C. vulgaris and N. pelliculosa, and toxic algae caused metabolic disorders, immune injury, and poor physiological status. The study has practical significance in the sustainable cultivation of H. cumingii and provides a theoretical basis for bivalve biomanipulation in eutrophic water.

Mussels Repair Shell Damage despite Limitations Imposed by Ocean Acidification

Bivalves frequently withstand shell damage that must be quickly repaired to ensure survival. While the processes that underlie larval shell development have been extensively studied within the context of ocean acidification (OA), it remains unclear whether shell repair is impacted by elevated pCO2. To better understand the stereotypical shell repair process, we monitored mussels (Mytilus edulis) with sublethal shell damage that breached the mantle cavity within both field and laboratory conditions to characterize the deposition rate, composition, and integrity of repaired shell. Results were then compared with a laboratory experiment wherein mussels (Mytilus trossulus) repaired shell damage in one of seven pCO2 treatments (400–2500 µatm). Shell repair proceeded through distinct stages; an organic membrane first covered the damaged area (days 1–15), followed by the deposition of calcite crystals (days 22–43) and aragonite tablets (days 51–69). OA did not impact the ability of mussels to close drill holes, nor the microstructure, composition, or integrity of end-point repaired shell after 10 weeks, as measured by µCT and SEM imaging, energy-dispersive X-ray (EDX) analysis, and mechanical testing. However, significant interactions between pCO2, the length of exposure to treatment conditions, the strength and inorganic content of shell, and the physiological condition of mussels within OA treatments were observed. These results suggest that while OA does not prevent adult mussels from repairing or mineralizing shell, both OA and shell damage may elicit stress responses that impose energetic constraints on mussel physiology.

Effects of in vivo exposures to nanoparticles (Al<sub>2</sub>O<sub>3</sub>, CuO, TiO<sub>2</sub>) on the activities of ATPases in the gill and muscle of freshwater mussel (Unio tigridis)

Mussels are effective bioindicator organisms for aquatic environments. Therefore, they were often used to determine the effects of various xenobiotics in the aquatic systems. There is no study to our knowledge on the in vivo effects of nanoparticles (NPs) on the activities of ATPases in freshwater mussels (Unio tigridis). This work demonstrates the effects of Al$_{2}$O$_{3}$, CuO, and TiO$_{2}$ NPs on Na- ATPase, Ca-ATPase, and Mg-ATPase activities in the gill and muscle of mussels following 14-day exposures to different concentrations of NPs (0, 1, 3, 9 mg/L). Mussels were fed with laboratory cultured algae (Chlorella vulgaris) during the exposures. There was no ouabainsensitive ATPase activity in the tissues of U. tigridis. The activities of Na-ATPase and Ca-ATPase in the gill decreased significantly (p < 0.05), while Mg-ATPase activity increased. However, the activities of all ATPases decreased significantly after NP exposures in the muscle. There were more significant alterations in the gill compared to the alterations in the muscle. The order of NP effects was determined as TiO$_{2}$ > CuO > Al$_{2}$O$_{3}$. There was no significant alteration in algae consumption between control and NP-exposed mussels. The present study reporting the first data on the effects of NPs in U. tigridis demonstrated the sensitivity of mussel physiology towards NP exposures, suggesting further studies to understand better the physiological response of mussels.

Cycles of heat and aerial-exposure induce changes in the transcriptome related to cell regulation and metabolism in Mytilus californianus

The intertidal mussel Mytilus californianus is subjected to thermal and oxygen cycles due to fluctuations of the tidal cycle. Mussels that reside in high-shore microenvironments experience extended periods of aerial-exposure and greater thermal challenges than low-shore populations. In this study, we investigated the combined effect of daily extended periods of aerial-exposure and midday thermal events on the physiology of mussels by monitoring transcriptome-wide gene expression in a simulated tidal environment. Mussels were acclimated to aerial-exposure for 20 h a day combined with a simulated midday solar heating event of + 8 °C. Results revealed that 11% of the transcriptome exhibited robust patterns of rhythmic gene expression. Two broad sets of genes were induced, including one that was upregulated during the daytime thermal stress period and another following the 4-h evening high-tide. The daytime thermal stress associated gene set was enriched for genes related to cellular regulatory pathways such as those that encode transcription factors while genes expressed following evening submergence varied in functional theme. Additionally, genes related to energy metabolism were also upregulated during warming periods of the tidal cycle. Comparing these data to published data from a previous tidal simulation study revealed that acclimation to daily heat stress yielded a muted transcriptional response to heat compared to an acute response observed in mussels maintained under isothermal conditions. These results indicate that M. californianus displays phenotypic plasticity with respect to transcriptomic expression and that this trait likely promotes homeostasis in the intertidal environment.

Biological rhythms in the deep-sea hydrothermal mussel Bathymodiolus azoricus

Biological rhythms are a fundamental property of life. The deep ocean covers 66% of our planet surface and is one of the largest biomes. The deep sea has long been considered as an arrhythmic environment because sunlight is totally absent below 1,000 m depth. In the present study, we have sequenced the temporal transcriptomes of a deep-sea species, the ecosystem-structuring vent mussel Bathymodiolus azoricus. We reveal that tidal cycles predominate in the transcriptome and physiology of mussels fixed directly at hydrothermal vents at 1,688 m depth at the Mid-Atlantic Ridge, whereas daily cycles prevail in mussels sampled after laboratory acclimation. We identify B. azoricus canonical circadian clock genes, and show that oscillations observed in deep-sea mussels could be either a direct response to environmental stimulus, or be driven endogenously by one or more biological clocks. This work generates in situ insights into temporal organisation in a deep-sea organism.

Ocean acidification and dynamic energy budget models: Parameterisation and simulations for the green-lipped mussel

Ocean acidification (OA), the change in ocean chemistry caused by carbon dioxide emissions, poses a serious imminent threat to marine organisms, especially those with calcium carbonate shells. The green-lipped mussel (Perna canaliculus), endemic to New Zealand, is common in coastal ecosystems and is an economically important aquaculture species. As a step towards supporting aquaculture management in a changing environment, we used a dynamic energy budget (DEB) model to investigate the potential influence of OA on growth and reproduction of the mussel. Zero-variate and growth data from local mussel farms were used to parameterise the model with the AmP method. The parameter estimation showed an acceptable goodness of fit, with a low mean relative error of 0.143 and the symmetric mean squared error of 0.125. The model was subsequently modified to estimate parameter values under OA conditions, based on data obtained from laboratory experiments where mussels were grown at future projected reduced pH (elevated pCO2) levels. The maintenance ([ṗM]) and volume-specific cost for growth ([EG]) were identified as the key parameters in response to OA. The model was then applied to simulate mussel energetics under pCO2 scenarios projected for 2050 and 2100. The model predicts that decreasing pH would cause reductions in shell length growth, flesh weight and reproductive capacity. As well as providing a quantitative tool for understanding the influence of OA on mussel physiology, this DEB model is also an important component of individual-based population and ecosystem models, enabling simulation of complex population and ecosystem level responses to OA.

Gene transcription patterns in response to low level petroleum contaminants in Mytilus trossulus from field sites and harbors in southcentral Alaska

The 1989 Exxon Valdez oil spill damaged a wide range of natural resources, including intertidal communities, and post-spill studies demonstrated acute and chronic exposure and injury to an array of species. Standard toxicological methods to evaluate petroleum contaminants have assessed tissue burdens, with fewer assays providing indicators of health or physiology, particularly when contaminant levels are low and chronic. Marine mussels are a ubiquitous and crucial component of the nearshore environment, and new genomic technologies exist to quantify molecular responses of individual mussels to stimuli, including exposure to polycyclic aromatic hydrocarbons (PAHs). We used gene-based assays of exposure and physiological function to assess chronic oil contamination using the Pacific blue mussel, Mytilus trossulus. We developed a diagnostic gene transcription panel to investigate exposure to PAHs and other contaminants and its effects on mussel physiology and health. During 2012–2015, we analyzed mussels from five field sites in western Prince William Sound, Alaska, with varying oil histories from the 1989 Exxon Valdez oil spill, and from three boat harbors in the area. Gene transcription patterns of mussels from harbors were consistent with elevated exposure to PAHs or other contaminants, whereas transcription patterns of mussels sampled from shorelines in areas affected by the oil spill indicated no PAH exposure.

Mytilus galloprovincialis (Lamarck, 1819) as host of Mytilicola orientalis (Mori, 1935) in the northern Adriatic Sea: presence and effect

The transfer of mariculture bivalves into new areas is increasing the risk of spreading Mytilicola copepods in native bivalve populations. Mytilicola orientalis was spread from Japan to native oysters and mussels in the Mediterranean. However, the presence of M. orientalis and its effect on the Mediterranean mussel, Mytilus galloprovincialis, are so far under-investigated. Our study shows the first identification of M. orientalis in mussels from the northern Adriatic Sea. M. orientalis was detected in mussels, from the Lim Bay, around the mariculture area of M. galloprovincialis. The adult stages of the copepod occur in mussels from May to August. The mean intensity of infestation and prevalence reached the maximum in August and was positively related to seawater temperature and salinity. We found one to three parasites per host individual, and most of the infested mussels were infested by one single parasite. Using the condition index, we found a relation between mussel physiology and seasonal cycle. Number of parasites was not related to the applied condition index. Our study established no difference in M. galloprovincialis condition index between infested and uninfested individuals, suggesting that the presence of M. orientalis does not adversely affect the mussel physiology to a measurable extent. However, our study reports the first record in the Adriatic Sea for M. orientalis.

Identification and Characterization of a Novel Family of Cysteine-Rich Peptides (MgCRP-I) from Mytilus galloprovincialis.

We report the identification of a novel gene family (named MgCRP-I) encoding short secreted cysteine-rich peptides in the Mediterranean mussel Mytilus galloprovincialis. These peptides display a highly conserved pre-pro region and a hypervariable mature peptide comprising six invariant cysteine residues arranged in three intramolecular disulfide bridges. Although their cysteine pattern is similar to cysteines-rich neurotoxic peptides of distantly related protostomes such as cone snails and arachnids, the different organization of the disulfide bridges observed in synthetic peptides and phylogenetic analyses revealed MgCRP-I as a novel protein family. Genome- and transcriptome-wide searches for orthologous sequences in other bivalve species indicated the unique presence of this gene family in Mytilus spp. Like many antimicrobial peptides and neurotoxins, MgCRP-I peptides are produced as pre-propeptides, usually have a net positive charge and likely derive from similar evolutionary mechanisms, that is, gene duplication and positive selection within the mature peptide region; however, synthetic MgCRP-I peptides did not display significant toxicity in cultured mammalian cells, insecticidal, antimicrobial, or antifungal activities. The functional role of MgCRP-I peptides in mussel physiology still remains puzzling.

Linking zebra mussel growth and survival with two cellular stress indicators during chronic temperature stress

Sessile aquatic invertebrates are at great risk for temperature stress. Changes in ambient temperature affect metabolic demands, thus altering energy budgets, and often reducing performance or survival of these species. Zebra mussels are highly invasive, yet little is known about their physiology under biologically relevant conditions, especially with regard to cellular parameters. This study examined the effect of temperature on zebra mussel physiology and investigated whether the levels of two cellular markers, HSP70 and AMPK activity, could serve as indicators of chronic thermal stress. Mussels were collected from a site in central Illinois, slowly acclimated to either 10, 20, or 30°C, and held at these temperatures for four weeks. Size, mortality, and the cellular markers were measured. Size and mortality data indicate heat stress at 30°C. Elevation in HSP70 levels confirmed this temperature elicits a stress response. Elevation in AMPK activity was not detected at 30°C, most likely indicating this temperature is beyond the scope for this marker, and therefore at or near the lethal limit. These data suggest this zebra mussel population experiences reduced performance and potential mortality in the field during summer months. Interestingly, cold acclimation resulted in a temporary elevation in AMPK activity, a result that has not been reported previously in ectotherms and is likely attributable to the metabolic demands of thermal acclimation.

Transcriptomic analysis of the mussel Elliptio complanata identifies candidate stress-response genes and an abundance of novel or noncoding transcripts.

Mussels are useful indicator species of environmental stress and degradation, and the global decline in freshwater mussel diversity and abundance is of conservation concern. Elliptio complanata is a common freshwater mussel of eastern North America that can serve both as an indicator and as an experimental model for understanding mussel physiology and genetics. To support genetic components of these research goals, we assembled transcriptome contigs from Illumina paired-end reads. Despite efforts to collapse similar contigs, the final assembly was in excess of 136,000 contigs with an N50 of 982 bp. Even so, comparisons to the CEGMA database of conserved eukaryotic genes indicated that ∼20% of genes remain unrepresented. However, numerous candidate stress-response genes were present, and we identified lineage-specific patterns of diversification among molluscs for cytochrome P450 detoxification genes and two saccharide-modifying enzymes: 1,3 beta-galactosyltransferase and fucosyltransferase. Less than a quarter of contigs had protein-level similarity based on modest BLAST and Hmmer3 statistical thresholds. These results add comparative genomic resources for molluscs and suggest a wealth of novel proteins and noncoding transcripts.

Seasonal variations of gene expression biomarkers in Mytilus galloprovincialis cultured populations: Temperature, oxidative stress and reproductive cycle as major modulators

The blue mussel Mytilus galloprovincialis has been used as monitoring organism in many biomonitoring programs because of its broad distribution in South European sea waters and its physiological characteristics. Different pollution-stress biomarkers, including gene expression biomarkers, have been developed to determine its physiological response to the presence of different pollutants. However, the existing information about basal expression profiles is very limited, as very few biomarker-based studies were designed to reflect the natural seasonal variations. In the present study, we analyzed the natural expression patterns of several genes commonly used in biomonitoring, namely ferritin, metallothionein, cytochrome P450, glutathione S-transferase, heat shock protein and the kinase responsive to stress KRS, during an annual life cycle. Analysis of mantle-gonad samples of cultured populations of M. galloprovincialis from the Delta del Ebro (North East Spain) showed natural seasonal variability of these biomarkers, pointing to temperature and oxidative stress as major abiotic modulators. In turn, the reproductive cycle, a process that can be tracked by VCLM7 expression, and known to be influenced by temperature, seems to be the major biotic factor involved in seasonality. Our results illustrate the influence of environmental factors in the physiology of mussels through their annual cycle, a crucial information for the correct interpretation of responses under stress conditions.

Histological Atlas of Freshwater Mussels (Bivalvia, Unionidae):Villosa nebulosa(Ambleminae: Lampsilini),Fusconaia cerina(Ambleminae: Pleurobemini) andStrophitus connasaugaensis(Unioninae: Anodontini)

Freshwater mussels (Mollusca: Bivalvia: Unionoida) are a species-rich group of parasitic bivalves comprising approximately 843 nominal species in six families, including 300 species of Unionidae and five of Margaritiferidae in North America. Unionid shells have been studied extensively for the purposes of taxonomy, but less information exists about the cellular anatomy of their “soft tissues” (mantle cavity tissues and visceral tissues). No systematic histological atlas of any unionid has been published in the peer-reviewed literature, and this lack of information hinders basic and applied research topics involving freshwater mussels. Herein, we describe the tissue and cell anatomy of a representative species from each of three lineages (tribes) of Unionidae sensu Graf & Cummings (2006) ranging in North America: Villosa nebulosa (Ambleminae: Lampsilini), Fusconaia cerina (Ambleminae: Pleurobemini) and Strophitus connasaugaensis (Unioninae: Anodontini). Based on necropsy observations and light microscopy of serial histological sections, for each species we describe and compare mantle cavity tissues (i.e., tissue enclosed by mantle: mantle, adductor muscle, pedal protractor, pedal retractor, gill, foot, labial palp) and visceral organs (i.e., internal organs: esophagus, digestive diverticulum, stomach, crystalline style sac, intestine, heart, nephridium, cerebral ganglia, pedal ganglia, visceral ganglia, ovaries and testes). We also present a synoptical review of pertinent literature on histological anatomy of unionids. The present study (i) represents the first histological atlas for freshwater mussels, (ii) comprises a baseline for monitoring mussel health in aquatic ecosystems, and (iii) could assist future workers studying freshwater mussel physiology, life history, toxicology, pathology, systematics and ecology.

Open water integrated multi-trophic aquaculture: constraints on the effectiveness of mussels as an organic extractive component

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 4:163-173 (2013) - DOI: https://doi.org/10.3354/aei00081 AS WE SEE IT Open water integrated multi-trophic aquaculture: constraints on the effectiveness of mussels as an organic extractive component Peter J. Cranford1,*, Gregor K. Reid2, Shawn M. C. Robinson2 1Fisheries and Oceans Canada, Bedford Institute of Oceanography, 1 Challenger Dr., Dartmouth, Nova Scotia B4C 4C9, Canada 2Canadian Integrated Multi-Trophic Aquaculture Network (CIMTAN), University of New Brunswick, PO Box 5050, Saint John, New Brunswick E2L 4L5, Canada *Email: peter.cranford@dfo-mpo.gc.ca ABSTRACT: Mussels are currently the primary species employed in open water integrated multi-trophic aquaculture (IMTA) systems to extract particulate organic fish waste (OFW) exiting fish net-pens. Information on mussel feeding and digestion physiology was used to identify constraints on the capacity of mussels to capture and absorb OFW under various open water IMTA scenarios. OFW capture by mussels is severely limited by the time available to intercept solid wastes contained in the horizontal particle flux. Intensive and spatially extensive mussel culture within IMTA systems could improve waste extraction, but maximum efficiency will ultimately be constrained by current velocity, available IMTA farm space, and any negative feedback effects on fish culture from flow reduction caused by mussel culture. The ability of mussels to absorb more of the ingested organic fish feces (OFF) than they egest as mussel feces (a waste biomitigation requirement) depends on the concentration of OFF available to mussels, relative to the ambient seston concentration and seston organic content. The biomitigation potential of mussels will be greatest where seston abundance is low and the organic content is high. Achieving maximum waste extraction by mussel co-culture entails depleting their particulate food supply to a level that may limit mussel production. Consequently, a constraint on waste extraction may be the desire to maximize profits from the extractive species. This study identified important constraints on the capacity of mussels to perform their intended role in IMTA systems that can only be partially addressed by optimizing system design. KEY WORDS: Integrated multi-trophic aquaculture · Organic fish waste · Mussel physiology · Biofiltration · Biomitigation · Organic enrichment Full text in pdf format PreviousNextCite this article as: Cranford PJ, Reid GK, Robinson SMC (2013) Open water integrated multi-trophic aquaculture: constraints on the effectiveness of mussels as an organic extractive component. Aquacult Environ Interact 4:163-173. https://doi.org/10.3354/aei00081 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 4, No. 2. Online publication date: July 25, 2013 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2013 Inter-Research.