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The present study is devoted to a comparison of the structure and quantitative ratio of heterogeneous spermatozoa of native wild mussels Mytilus trossulus Gould, 1850, collected in four areas of the Peter the Great Bay of the Sea of Japan (the northwestern part of the Pacific Ocean). The mussels were identified as M. trossulus by shell appearance, and the species was confirmed by sequencing the mitochondrial cytochrome c oxidase subunit I gene (COI). Heteromorphic spermatozoa were found; namely, a total of eight morphs (SPERM1–SPERM8) in M. trossulus. Surprisingly, some of the detected sperm morphs overlap morphologically with the sperms of other mytilids such as M. edulis, Crenomytilus (M.) grayanus and M. coruscus. Possible reasons for this phenomenon are discussed. In each geographic area, the 'quantitative proportions of heterogeneous spermatozoa' (QPHS) were unique. It has been suggested that the QPHS score can be considered in the context of its applicability as a biological marker for finding optimal mussel rearing sites. [ABSTRACT FROM AUTHOR]

Mussels occupy a key middle trophic position in nearshore food webs linking primary producers to predators. Climate‐related environmental changes may synergistically combine with changes in predator abundance to affect intertidal ecosystems. We examined the influence of two major events on mussel (Mytilus trossulus) abundance in the northern Gulf of Alaska: the recent Pacific marine heatwave (PMH, 2014–2016) and an outbreak of sea star wasting (SSW). We investigated how mussel abundance changed since the onset of SSW and whether the density of predatory sea stars or PMH‐related temperature metrics explain variation in mussel abundance. Sea stars and mussels were surveyed since 2005 approximately annually in four regions of the northern Gulf of Alaska: Katmai (KATM), Kachemak Bay (KBAY), Kenai Fjords (KEFJ) and western Prince William Sound (WPWS). Mussel percent cover in the mid‐intertidal increased 1–3 years after declines in sea stars at all regions and in the low‐intertidal at KATM, KBAY, and KEFJ, but not at WPWS. After the onset of SSW, large (≥20 mm length) mussel density and mussel bed width increased at KATM but not the other regions. Total mussel densities, including recruits, did not differ before and after the onset of SSW. The total number of sea stars significantly explained variation in mussel metrics, but the proportions of the three sea star species examined did not. We did not find strong evidence for direct effects of temperature on mussels. The effects of the PMH and the SSW outbreak appear to have combined, with increased temperatures indirectly benefiting mussels in concert with relaxed top‐down pressure from sea stars, allowing for increased mussel abundance. Changing mussel abundance may affect intertidal local productivity and the abundance or performance of other nearshore consumers of mussels. [ABSTRACT FROM AUTHOR]

In the commercial Pacific mussel species, Mytilus trossulus, from the Sea of Japan, features of the morphological structure of the byssal apparatus, byssal threads, and pedal groove are studied. Steps in the process of byssal threads formation and characters of the morphological structure of the byssal groove related to this process are described in M. trossulus. The byssal apparatus is shown to consist of a root, a stem, and byssal threads, the latter in cross section being ellipsoid in shape. A byssal thread consists of a corrugated proximal part located immediately behind the cuff and is one-third of its length, and a relatively smooth and flexible distal part taking up two-thirds of the thread length and ending with an attachment disk at the distal end. On the surface of the attachment disk, three reinforcing cords are situated. The morphological features observed in these structures are discussed in terms of the spatial distribution of mytilids in marine coastal zones, a successful habitat of M. trossulus being rocky shores with active wave activities. [ABSTRACT FROM AUTHOR]

The potential productivity of oysters and mussels was estimated for Voevoda Bay (Russky Island, Primorskii krai) using the FARM model. The main sources of primary production in the study area are seagrass (Zostera marina) and phytoplankton (diatoms). The area of Zostera growth was delineated based on the bottom survey of the bay. The parameters of organic matter production of Zostera and phytoplankton for each computational grid cell were modeled using the ECO BLOOM II Algae module, which is part of the DELWAQ model of the Delft3D software package. Spatial redistribution of organic matter, chlorophyll a and phytoplankton were simulated using the results of hydrodynamic modelling of the DELFT3D Flow. The values of biological (primary production) and hydrochemical (temperature, salinity, oxygen content) parameters, obtained for each computational grid cell were used as input to the FARM. The empirical exceedance probability curves of modelled productivity for pasture and cage cultivation of the giant oyster (Crassostrea gigas) and the Pacific mussel (Mytilus trossulus) were calculated for each cell. The spatial distribution for the potential productivity values of the representative exceedance probability (50, 75, and 95%) for both types of cultivation was mapped. [ABSTRACT FROM AUTHOR]

The biomechanics of specialized mechanical structures produced by organisms provides crucial fitness advantages. The energetic cost associated with producing these structural materials and the resulting energetic trade‐off with growth, however, is rarely quantified. We integrate resource allocation to structural material production with an energetic framework by combining an experimental manipulation with an energetic model.Mytilid bivalves produce byssus, a network of collagen‐like threads that tethers individuals to hard substrate. We hypothesized that a manipulation that induces the production of more byssal threads would result in increased energetic cost and decreased growth of the species Mytilus trossulus.In month‐long field experiments in spring and autumn, we severed byssal threads across a range of frequencies (never, weekly, daily), and measured shell and tissue growth. We then quantified the costs associated with the production of byssal threads using a Scope for Growth model.We found that byssal thread removal increased byssal thread production and decreased growth. The cost calculated per byssal thread was similar in the spring and autumn (~1 J/thread), but energy budget calculations differed by season, and depended on thread quantity and seasonal differences in assumptions of metabolic costs.This work demonstrates that the cost of producing a structural material has a substantial effect on mussel energetic state. The energetic cost of producing byssal threads was 2%–8% percent of the energy budget in control groups that had low byssal thread production, and increased six to 11‐fold (up to 47%) in mussels induced to produce threads daily.We propose that characterizing the trade‐off between the cost of biomaterial production and growth has implications for understanding the role of trade‐offs in adaptive evolution, and improved natural resource management and conservation practices. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Understanding and predicting responses of ectothermic animals to temperature are essential for decision-making and management. The thermal performance curve (TPC), which quantifies the thermal sensitivity of traits such as metabolism, growth and feeding rates in laboratory conditions, is often used to predict responses of wild populations. However, central assumptions of this approach are that TPCs are relatively static between populations and that curves measured under stable temperature conditions can predict performance under variable conditions. We test these assumptions using two latitudinally matched populations of the ecosystem engineer Mytilus trossulus that differ in their experienced temperature variability regime. We acclimated each population in a range of constant or fluctuating temperatures for six weeks and measured a series of both short term (feeding rate, byssal thread production) and long-term (growth, survival) metrics to test the hypothesis that performance in fluctuating temperatures can be predicted from constant temperatures. We find that this was not true for any metric, and that there were important interactions with the population of origin. Our results emphasize that responses to fluctuating conditions are still poorly understood and suggest caution must be taken in the use of TPCs generated under constant temperature conditions for the prediction of wild population responses. [ABSTRACT FROM AUTHOR]

Two lineages of bivalve transmissible neoplasia (BTN), BTN1 and BTN2, are known in blue mussels Mytilus. Both lineages derive from the Pacific mussel M. trossulus and are identified primarily by their unique genotypes of the nuclear gene EF1α. BTN1 is found in populations of M. trossulus from the Northeast Pacific, while BTN2 has been detected in populations of other Mytilus species worldwide but not in M. trossulus itself. Here we examined M. trossulus from the Sea of Japan (Northwest Pacific) for the presence of BTN. Using hemocytology and flow cytometry of the hemolymph, we confirmed the presence of disseminated neoplasia in our specimens. Cancerous mussels possessed the BTN2 EF1α genotype and two mitochondrial haplotypes with different recombinant control regions, similar to that of common BTN2 lineages. This is the first report of BTN2 in its original host species M. trossulus. A comparison of all available BTN and M. trossulus COI sequences suggests a common and recent origin of BTN2 diversity in populations of M. trossulus outside the Northeast Pacific, possibly in the Northwest Pacific. [ABSTRACT FROM AUTHOR]

Abstract The gene of mtl from the mussel Mytilus trossulus was cloned into pET-40b(+) expression vector. After expression in E. coli using designed MX-medium an instable soluble form of MTL was obtained. The developed isolation method of the recombinant protein in "semi-denatured" conditions allowed obtaining an active soluble form of the homogenous lectin from the mussel M. trossulus (r-MTL). Both of the lectins had similar antigenic and spatial structures. Highlights • The recombinant analog of Mytilus trossulus lectin, a member of new lectin family was obtained in soluble and active form. • A method of isolation of the recombinant protein in "semi-denatured" conditions was developed. • It has been shown that native MTL and recombinant MTL have similar spatial structures and biological activity. [ABSTRACT FROM AUTHOR]

Anthropogenic warming of the ocean and atmosphere, concurrent with ocean acidification and deoxygenation, has made it even more pressing to quantify the link between environmental stressors and marine organism population dynamics. In marine environments, low food availability, low feeding rates, and/or increased metabolic costs can cause energetic limitation. Energetic limitation affects some functional traits, such as growth rates of body tissue and reproductive output. Other functional traits that are linked with short-term survival are often prioritized in conditions of energy limitation, despite their energetic cost. Mussels are ecosystem engineers in rocky shore ecosystems, and they produce byssal threads to attach to hard substrate and aquaculture line. Previous studies of mytilid mussel bioenergetics suggest tissue and shell growth are energetically-constrained, while production of byssal threads presents a fitness trade-off and could potentially be a fixed or 'constitutive' response regardless of energetic state. In this study, we conduct a field test with two congener mussel species, Mytilus trossulus and Mytilus galloprovincialis to determine whether an index of energetic availability, scope for growth (SFG), correlates with growth and byssal thread production, and the extent to which other potential stressors (hypoxia, low pH, low salinity and high temperature) modulate this response. We find a positive correlation between SFG and growth (both tissue and shell) but not the number of byssal threads produced. We also find low pH or low DO, two co-varying physiological stressors, negatively affect tissue growth of both species, but only marginally affect byssal thread production. We also observed mortality in the late summer/early autumn that coincides with the period of greater hypoxia and low pH. Overall, this work suggests that some functional traits, such as shell and tissue growth, are energetically-constrained while other functional traits, such as mussel byssal thread production, may be best described as a fitness trade-off. [Display omitted] • Mussel growth and mechanical attachment (byssal thread production) evaluated in response to environmental conditions at a mussel farm. • Energetics framework was used to predict feeding rate and metabolic cost as functions of temperature. • Energetics was a significant predictor of mussel growth. • Duration of co-occurring hypoxia / low pH, prevalent at depth, was also a predictor of mussel growth. • Suggests byssal thread production is constitutive and not a 'flexible' trait across a gradient of energy limitation. [ABSTRACT FROM AUTHOR]

The role of seawater NOM in reducing metal toxicity for marine organisms is not well understood. We investigated the effects of five different marine NOMs (two autochthonous, one allochthonous, two of mixed origin, at 8 mg C/L), three metals (6 μg Cu/L; 20 μg Pb/L; 25 μg Zn/L), and combinations between them, to early life stages of Mytilus trossulus (a North Pacific native) in 48-h tests. Endpoints were whole body Ca 2+ +Mg 2+ -ATPase activity, carbonic anhydrase (CA) activity and lipid peroxidation. Comparisons were made with previously reported tests (identical conditions) on the invasive M. galloprovincialis . Unexposed M. trossulus had lower Ca 2+ +Mg 2+ -ATPase but similar baseline CA activity and lipid peroxidation to unexposed M. galloprovincialis . NOMs alone induced increased enzyme activities, and increased lipid peroxidation, but the latter did not occur with NOMs of mixed origin in M. trossulus . There was no clear difference in the sensitivity to various NOMs between species. In M. trossulus , all three metals by themselves caused increases in lipid peroxidation, as did many metal-NOM combinations. The origin of the NOMs influenced the nature of the responses to NOM-metal combinations in both species, but no clear relationship to NOM chemistry was apparent. Overall, M. trossulus was more sensitive to metals and NOM-metal combinations, with a greater number of significant responses (27 versus 22 treatment endpoints, out of a total of 72) and a greater proportion of negative effects (81% versus 50%) than in M. galloprovincialis. Therefore, marine NOMs by themselves, as well as metals by themselves and NOM-metal combinations, can induce both positive and negative physiological responses. Lipid peroxidation appears to be a particularly common negative response. In future studies, NOM quality and mussel species should be considered since native M. trossulus and invasive M. galloprovincialis exhibited markedly different responses after exposure to the same environmental conditions. [ABSTRACT FROM AUTHOR]

This paper describes changes in the content of free steroid hormones e.g. testosterone (T), estradiol-17β (E2), estrone (E1) and estriol (E3) of Mytilus trossulus from the southern Baltic Sea as a function of season, stage of gametogenesis, sex, tissue (gonadal and somatic) and depth. The highest levels of T, E2, E1 and E3 were found in mussels sampled in spring and summer while the lowest levels were found in winter. This pattern was stable and was seen in both sexes and tissues in mussels from both mussel beds. The spring and summer peaks in steroid levels (SL) coincided with advanced levels of gametogenesis (the highest gonadal index, GI) of our model species. But, the lowest GI (autumn) and the lowest steroids content (winter) did not overlap. Instead, water temperature increase was followed by increase of SL and vice versa. This suggests that steroids may not be actively involved in the early stages of gamete development and does not preclude them from potentially being involved as endogenous modulators in the final stages of reproduction (e.g. spawning). Hence, observed fluctuations in SL in our model species are unlikely to be caused by reproductive cycle but are rather of unknown nature, likely linked with environmental conditions. Sex-related differences in steroid content included estrogen domination in females and androgen domination in males. A trend towards higher level of steroids in gills than in gonads was found, supporting the hypothesis about an exogenous origin of steroids in bivalves. However, based on the present results, we cannot exclude the possibility that these steroids have both an endogenous and exogenous origin. [ABSTRACT FROM AUTHOR]

Sea stars Asterias rubens are important natural enemies of the blue mussel Mytilus in the North Atlantic. We asked whether these predators distinguish between the cryptic species M. edulis and M. trossulus that occur sympatrically in the White Sea. In mixed experimental stocks, the odds of being eaten by sea stars were about four times greater for M. trossulus. We also showed that A. rubens preferred smaller mussels to larger ones, irrespective of their species affinity. Our findings support earlier indirect observations showing that sea stars recognize M. trossulus as a more preferable prey than M. edulis. Dramatic differences in the vulnerability to sea star predation may explain the segregation of habitats between the two mussel species in contact zones; M. trossulus usually tends to occupy habitats where the sea star predators are scarce. [ABSTRACT FROM AUTHOR]

Abstract: A key component to understanding the evolutionary response to a changing climate is linking underlying genetic variation to phenotypic variation in stress response. Here, we use a genome‐wide association approach (GWAS) to understand the genetic architecture of calcification rates under simulated climate stress. We take advantage of the genomic gradient across the blue mussel hybrid zone (Mytilus edulis and Mytilus trossulus) in the Gulf of Maine (GOM) to link genetic variation with variance in calcification rates in response to simulated climate change. Falling calcium carbonate saturation states are predicted to negatively impact many marine organisms that build calcium carbonate shells – like blue mussels. We sampled wild mussels and measured net calcification phenotypes after exposing mussels to a ‘climate change’ common garden, where we raised temperature by 3°C, decreased pH by 0.2 units and limited food supply by filtering out planktonic particles >5 μm, compared to ambient GOM conditions in the summer. This climate change exposure greatly increased phenotypic variation in net calcification rates compared to ambient conditions. We then used regression models to link the phenotypic variation with over 170 000 single nucleotide polymorphism loci (SNPs) generated by genotype by sequencing to identify genomic locations associated with calcification phenotype, and estimate heritability and architecture of the trait. We identified at least one of potentially 2–10 genomic regions responsible for 30% of the phenotypic variation in calcification rates that are potential targets of natural selection by climate change. Our simulations suggest a power of 13.7% with our study's average effective sample size of 118 individuals and rare alleles, but a power of >90% when effective sample size is 900. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Protein–protein interactions play a central role in the gamete attraction, binding, and fusion stages of gamete interactions and fertilization for broadcast spawning species, such as marine mussels in theMytilus edulisspecies complex. Although assortative gamete interaction has been implicated in the level of reproductive isolation among the three species in this complex, the molecular basis of these interactions has not been elucidated. Using mass spectrometry peptide sequencing, cDNA sequencing, and bioinformatics approaches, we have investigated species-level variation in the proteins expressed on the surface of mussel eggs. We herein describe an extracellular protein, MESP-1, from the surface of the eggs ofM. edulisandM. trossulusthat has a unique domain structure when compared to protein structures that have heretofore been identified. Given variation in the size of MESP-1 predicted from cDNA sequences versus those estimated from SDS-PAGE gels, we conclude this protein is subject to significant species-specific post-translation modifications. Further, bioinformatic analysis of the novel structure of MESP-1 suggests that this protein may be an integral membrane protein involved in sperm–egg fusion, and/or released to the vitelline envelope. [ABSTRACT FROM AUTHOR]

The blue mussels Mytilus galloprovincialis and M. trossulus are competing species with biogeographical ranges set in part by environmental exposure to heat and hyposalinity. The underlying cellular mechanisms influencing interspecific differences in stress tolerance are unknown, but are believed to be under regulation by sirtuins, nicotinamide adenine dinucleotide (NAD+)-dependent deacylases that play a critical role in the cellular stress response. A comparison of the proteomic responses of M. galloprovincialis and M. trossulus to an acute heat shock in the presence and absence of the sirtuin inhibitor suramin (SIRT1, 2 and 5) showed that sirtuins affected molecular chaperones, oxidative stress proteins, metabolic enzymes, cytoskeletal and signaling proteins more in the heatsensitive M. trossulus than in the heat-tolerant M. galloprovincialis. Interactions between sirtuin inhibition and changes in the abundance of proteins of β-oxidation and oxidative stress in M. trossulus suggest a greater role of sirtuins in shifting metabolism to reduce the production of reactive oxygen species near thermal limits. Furthermore, RNA-binding proteins initiating and inhibiting translation were affected by suramin in M. galloprovincialis and M. trossulus, respectively. Western blot analysis showed that the levels of mitochondrial sirtuin 5 (SIRT5) were generally three times higher and increased with acute heat stress in response to sirtuin inhibition in M. trossulus but not in M. galloprovincialis, suggesting a possible feedback response in the former species and a greater reliance on SIRT5 for its stress response. Our findings suggest that SIRT5 plays an important role in setting interspecific differences in stress tolerance in Mytilus by affecting the stress proteome. [ABSTRACT FROM AUTHOR]

In a temporal comparison over 18 years, we documented changes in the position and structure of the North European blue mussel hybrid zone in the Öresund strait, between Mytilus edulis of the marine Kattegat and Mytilus trossulus of the brackish Baltic Sea. In 1987 the midpoint of the 140-km wide multilocus allozyme cline in shallow-water populations was estimated to be located half-way along the strait. In 2005, it was shifted 25 km towards the Baltic end of the Öresund, and was located near the fixed link (bridge) that was built across the strait meanwhile in the 1990s. The cline also appeared to have become narrower and the extent of hybridity among individuals decreased. Factors that theoretically can control the position and shape of a clinal hybrid zone involve environmental gradients between habitats that differentially favor the two hybridizing taxa, or barriers to geographical dispersal of the organism. We consider two alternative hypotheses to explain the movement of the mussel hybrid zone. (1) Environmental change related to climate warming: the more stenothermal M. trossulus was pushed out from the Öresund towards the cool Baltic by elevated temperatures. (2) Change of dispersal dynamics: the construction of the fixed link locally affected mussel dispersion which attracted the zone. We raise the question whether similar changes have taken place also in the other euryhaline taxa where genetic clines between Baltic vs. Kattegat populations occur. [ABSTRACT FROM AUTHOR]

Doubly uniparental inheritance of mitochondria (DUI) is best known in the blue mussel Mytilus. Under this model, two types of mitochondrial DNA exist: female type (F), transmitted from females to offspring of both genders, and male type (M), transmitted exclusively from males to sons. The mitogenomes are usually highly divergent, but an occasional replacement of a typical M genome by a particular F genome has been postulated to explain reduction of this divergence. Disruption of the DUI model has been reported in hybridization areas. Here, we present a new case of DUI disruption in a hybrid M. trossulus/M. edulis population from the North Sea (Norway). No M haplotypes derived from M. trossulus were identified in this population. Typical M haplotypes derived from M. edulis (ME) were rare. Two F-type haplogroups were found: one derived from M. edulis (FE) and the second derived from M. trossulus (FT). Many haplotypes from the FT group were recombinants, with the male CR sequence coming from the M. trossulus genome (FT1 haplogroup) in contrast to M. edulis CR as in the Baltic. FT1 haplotypes were abundant in the studied population, including homoplasmic females. However, males significantly more often carried these haplotypes; therefore, male heteroplasmy involved the original FE and recombinant FT, indicating that the FT genome undergoes masculinization. Structural similarity of FT1 CR with previously reported, masculinized Baltic haplotypes, which were derived from FE/ME recombination, provides further evidence that CR M-F recombination is a prerequisite for masculinization, also in the context of native M. trossulus mtDNA. [ABSTRACT FROM AUTHOR]

Ecological mussel farming in the Baltic Sea has gained attention due to ability of mussels to bind high concentrations of nitrogen and phosphorus in their tissues. Removal of mussels could serve as abatement of eutrophication. The Latvian coast of the Baltic Sea is one of the most exposed coastlines of the Baltic due to the highest wind and wave energy. Experimental units for mussel recruitment were placed in three locations at 15, 20 and 25 m depth assess the potential for mussel farming. The spawning maximum was observed in the middle of May, followed by recruitment in June. Recruitment of Mytilus was observed on all experimental units with higher densities at 6 to 10 m depth. Observations suggest that mussels can use artificial substrate for recruitment even near high energy shores. However, if mussel farming is to take place, submerged offshore farming techniques should be considered. [ABSTRACT FROM AUTHOR]

While secondary contact between Mytilus edulis and Mytilus trossulus in North America results in mosaic hybrid zone formation, both species form a hybrid swarm in the Baltic. Despite pervasive gene flow, Baltic Mytilus species maintain substantial genetic and phenotypic differentiation. Exploring mechanisms underlying the contrasting genetic composition in Baltic Mytilus species will allow insights into processes such as speciation or adaptation to extremely low salinity. Previous studies in the Baltic indicated that only weak interspecific reproductive barriers exist and discussed the putative role of adaptation to environmental conditions. Using a combination of hydrodynamic modelling and multilocus genotyping, we investigate how oceanographic conditions influence passive larval dispersal and hybrid swarm formation in the Baltic. By combining our analyses with previous knowledge, we show a genetic transition of Baltic Mytilus species along longitude 12°-13°E, that is a virtual line between Malmö (Sweden) and Stralsund (Germany). Although larval transport only occurs over short distances (10-30 km), limited larval dispersal could not explain the position of this genetic transition zone. Instead, the genetic transition zone is located at the area of maximum salinity change (15-10 psu). Thus, we argue that selection results in weak reproductive barriers and local adaptation. This scenario could maintain genetic and phenotypic differences between Baltic Mytilus species despite pervasive introgressive hybridization. [ABSTRACT FROM AUTHOR]

Sporocysts with cercariae of Prosorhynchus squamatus Odhner, 1905 (Digenea, Bucephalidae) have been found for the first time in mussels Mytilus trossulus Gould, 1850 from the Gulf of Gdansk (the southern Baltic Sea). The presented work provides a description and morphometry of larvae of this parasite. [ABSTRACT FROM AUTHOR]

The occurrence of freshwater harmful algal bloom toxins impacting the coastal ocean is an emerging threat, and the potential for invertebrate prey items to concentrate toxin and cause harm to human and wildlife consumers is not yet fully recognized. We examined toxin uptake and release in marine mussels for both particulate and dissolved phases of the hepatotoxin microcystin, produced by the freshwater cyanobacterial genus Microcystis . We also extended our experimental investigation of particulate toxin to include oysters ( Crassostrea sp.) grown commercially for aquaculture. California mussels ( Mytilus californianus ) and oysters were exposed to Microcystis and microcystin toxin for 24 h at varying concentrations, and then were placed in constantly flowing seawater and sampled through time simulating riverine flushing events to the coastal ocean. Mussels exposed to particulate microcystin purged the toxin slowly, with toxin detectable for at least 8 weeks post-exposure and maximum toxin of 39.11 ng/g after exposure to 26.65 μg/L microcystins. Dissolved toxin was also taken up by California mussels, with maximum concentrations of 20.74 ng/g after exposure to 7.74 μg/L microcystin, but was purged more rapidly. Oysters also took up particulate toxin but purged it more quickly than mussels. Additionally, naturally occurring marine mussels collected from San Francisco Bay tested positive for high levels of microcystin toxin. These results suggest that ephemeral discharge of Microcystis or microcystin to estuaries and the coastal ocean accumulate in higher trophic levels for weeks to months following exposure. [ABSTRACT FROM AUTHOR]

The round goby Neogobius melanostomus has successfully invaded much of the Baltic Sea. However, very little is known about the feeding habits of the species in this newly invaded environment. Our laboratory experiment showed that the round goby is able to effectively consume a diverse variety of prey when given the choice between dominant benthic invertebrates: bivalves ( Macoma balthica, Mytilus trossulus, Cerastoderma glaucum) and amphipods ( Gammarus spp.). In contrast consumption of the gastropod ( Theodoxus fluviatilis) was very low in all provided combinations. Nevertheless, the round goby had no statistically significant preference towards any of the prey taxa. The round goby exhibited size-specific consumption of M. trossulus, with smaller individuals being consumed at least 25% more than larger size classes. In addition elevated prey density resulted in higher consumption of prey by the fish. The broad diet suggests that shifting densities of benthic invertebrate prey has little influence on the further dispersal of the round goby in the Baltic Sea as the species is potentially able to switch between several native invertebrate taxa. This opportunistic feeding behaviour has likely favoured this invasion and ensured success of the species in the invaded ecosystem. [ABSTRACT FROM AUTHOR]

Mussels ( Mytilus trossulus ) were caged along a known pollution gradient in the inner Archipelago Sea (northern Baltic Sea) and retrieved after 71 and 121 d for the measurement of selected chemical contaminants in tissues and biological endpoints including biochemical biomarkers and growth. Additional samples were collected during the growth season from a native mussel population at an alleged reference site. Elevated concentrations of numerous contaminants (e.g., PAH) were observed in spring, apparently due to the loss of tissue mass during the winter, while also the levels of many biomarkers (e.g., glutathione S -transferase activity) were elevated. Spatial and temporal changes in the accumulation of contaminants and biological parameters were observed with some of them (e.g., growth) linked to seasonal changes in environmental factors. The results underline the importance of understanding the effects of seasonal natural factors on the growth dynamics and general condition of mussels when assessing tissue concentrations of contaminants and biological effects. [ABSTRACT FROM AUTHOR]

In contemporary ecosystems, organisms are increasingly confronted with suboptimal living conditions. We aimed to understand the role of ecosystem engineering species in suboptimal habitats from a population inhabiting the species range margin in naturally stressful conditions. We determined the impact of 2–4 cm sized patches of dwarfed mussels Mytilus trossulus close to its lower salinity limit in the North-Eastern Baltic Sea, on epibenthic community patterns. Mussels affected total macrofaunal abundance and biomass and the taxonomic and functional community structure based on abundances, as well as the species composition of macrofauna. Mussels did not affect ephemeral algae or sediment chlorophyll content, but increased the abundance, biomass, richness, and diversity of grazers, within a radius approximately twelve times the size of mussel patches. We can expect marginal populations of ecosystem engineers in suboptimal habitats to contribute to spatial heterogeneity in biotic patterns and eventual ecosystem stability. [ABSTRACT FROM AUTHOR]

In the present study, a new Gal/GalNAc specific lectin from the mussel Mytilus trossulus (designated as MTL) was identified, and its expression levels, both in tissues and toward pathogen stimulation, were then characterized. The MTL primary structure was determined via cDNA sequencing. Deduced sequence of 150 amino acid residues showed 89% similarity to lectins from the mussels Crenomytilus grayanus and Mytilus galloprovincialis that were the first members of a new family of zoolectins. The results indicated that the MTL might be involved in immune response toward pathogen infection, and it might perform different recognition specificity toward bacteria or fungi. [ABSTRACT FROM AUTHOR]

The aim of this study was to identify and quantify natural steroid hormones (17β-estradiol E2, estriol E3, estrone E1, testosterone T) and xenoestrogen (17α-ethinylestradiol EE2) in gills and gonads of Mytilus trossulus from the Gulf of Gdańsk, Poland, using the LC–MS technique based on the enzymatic digestion of tissues, SPE extraction, and subsequent LC–MS analysis of the eluates. As a result, spatial differences in several steroid hormone concentrations were detected. While the highest concentrations of testosterone and natural estrogens were documented in mussels collected at the reference station (app. 13 ng g −1 wet weight for T, 9 ng g −1 w.w. for E2 and 3.5 ng g −1 w.w. for E1), decreased levels of natural steroids and increased levels of 17α-ethinylestradiol (EE2) were determined in individuals from the sewage treatment plant zone (app. 5 ng g −1 w.w. for T, 3 ng g −1 w.w. for E1, 1 ng g −1 w.w. for E2 and E3, 1 ng g −1 w.w. for EE2). No statistically significant tissue-related changes in steroids concentrations were found, but a trend towards higher steroids level in gills than in gonad was observed. [ABSTRACT FROM AUTHOR]

The applicability of immune responses in transplanted Baltic blue mussels ( Mytilus trossulus ) as biomarkers of immunotoxic effects was studied at differently contaminated locations in the Gulf of Bothnia (northern Baltic Sea). Here, we present a detailed report on the immune responses measured as complementary part of transplantation study by Turja et al. (2014). Various immunological endpoints such as total and differential cell count, morphological alterations, phagocytic activity, and caspase 3/7 activity of mussel haemocytes as well as haemolytic activity of the haemolymph were used. Mussels collected at a reference site at a Finnish coastal site (Hanko, H) were transplanted at the Swedish coast near industrial and urban regions of the cities Sundsvall (S1, S2) and Gävle (G1, G2), respectively. Based on the measured immunological responses, multivariate statistical analysis (PCA biplot) showed a clear separation of the most polluted site S1, indicating immunotoxic impacts of the mixture of contaminants present at this location. Based on these observations and results from Turja et al. (2014), we suggest the implementation of immunotoxic biomarkers for the evaluation of ecosystem health. However, these should be accompanied by complementary endpoints of biological effects encompassing i.e., physiological, antioxidant and bioenergetic markers. [ABSTRACT FROM AUTHOR]

Integrins play a key role in the intermediation and coordination between cells and extracellular matrix components. In this study, we first determined the presence of the β integrin-like protein and its presumptive ligand, fibronectin-like protein, during development and in some adult tissues of the bivalve mollusc Mytilus trossulus. We found that β integrin-like protein expression correlated with the development and differentiation of the digestive system in larvae. Besides the presence of β integrin-like protein in the digestive epithelial larval cells, this protein was detected in the hemocytes and some adult tissues of M. trossulus. The fibronectin-like protein was detected firstly at the blastula stage and later, the FN- LP-immunoreactive cells were scattered in the trochophore larvae. The fibronectin-like protein was not expressed in the β integrin-positive cells of either the veliger stage larvae or the adult mussel tissues and the primary hemocyte cell culture. Despite the β integrin- and fibronectin-like proteins being expressed in different cell types of mussel larvae, we do not exclude the possibility of direct interaction between these two proteins during M. trossulus development or in adult tissues. [ABSTRACT FROM AUTHOR]

Benthic suspension feeding mussels are an important functional guild in coastal and estuarine ecosystems. To date we lack information on how various environmental gradients and biotic interactions separately and interactively shape the distribution patterns of mussels in non-tidal environments. Opposing to tidal environments, mussels inhabit solely subtidal zone in non-tidal waterbodies and, thereby, driving factors for mussel populations are expected to differ from the tidal areas. In the present study, we used the boosted regression tree modelling (BRT), an ensemble method for statistical techniques and machine learning, in order to explain the distribution and biomass of the suspension feeding mussel Mytilus trossulus in the non-tidal Baltic Sea. BRT models suggested that (1) distribution patterns of M. trossulus are largely driven by separate effects of direct environmental gradients and partly by interactive effects of resource gradients with direct environmental gradients. (2) Within its suitable habitat range, however, resource gradients had an important role in shaping the biomass distribution of M. trossulus. (3) Contrary to tidal areas, mussels were not competitively superior over macrophytes with patterns indicating either facilitative interactions between mussels and macrophytes or co-variance due to common stressor. To conclude, direct environmental gradients seem to define the distribution pattern of M. trossulus, and within the favourable distribution range, resource gradients in interaction with direct environmental gradients are expected to set the biomass level of mussels. [ABSTRACT FROM AUTHOR]

In this study, we focus on the specific contribution of β integrin-like protein to adhesion-mediated events in molluscan larval cells in culture that could not have been investigated within the whole animal. An analysis of disturbances to cell-substratum adhesion, caused by the integrin receptor inhibiting Arg-Gly-Asp-Ser (RGDS)-peptide, the Ca/Mg-chelators and the stress influence of freezing-thawing, reveals that all these factors resulted in the partial destruction of the integrin-extracellular matrix (ECM) interaction in culture and, in particular, changes in the distribution and relative abundance of β integrin-positive cells. The experiments, carried out on selected substrates, found that β integrin-positive cells demonstrate different affinities for the substrates. This finding further supports the assumption that epithelial differentiation in cultivated cells of larval Mytilus may be mediated by β integrin-like proteins via binding to laminin; direct binding to other components of the ECM could not be demonstrated. The mussel β integrin-positive cells are not involved in myogenic or neuronal differentiation on any of the substrates but part of them has tubulin-positive cilia, forming some epithelia-like structures. Our data indicate that β integrin-positive cells are able to proliferate in vitro which suggests that they could participate in renewing the digestive epithelium in larvae. The findings provide evidence that the distribution pattern of β integrin-like protein depends on the cell type and the factors influencing the adhesion. [ABSTRACT FROM AUTHOR]

California mussel ( Mytilus californianus ) are ubiquitous shellfish species in coastal archaeological sites throughout western North America but are often highly fragmentary when recovered in small-volume ‘column’ or ‘bulk’ samples typically used to quantify shellfish assemblages. Archaeological research has predominantly focused on evaluating the dietary contribution of Mytilus but most studies assume an average meat weight or use categorical size classifications to determine subsistence strategies and harvest profiles. In this paper, we develop and evaluate a regression-based method for estimating shell length and meat weight for fragmentary Mytilus remains. Our regressions are based on live-collected M . californianus specimens from multiple locations in California and British Columbia and provide considerable statistical confidence for predicting length and meat weight. We also apply the same regressions to a collection of Mytilus trossulus and show similar predictive equations, indicating this method can be used in cases where it is not possible to distinguish morphologically between M. californianus and M. trossulus . We demonstrate how these results improve upon previous size-classification methods and discuss the potential for applying these measurements to enhance the relevance of these zooarchaeological data for modern marine conservation and management efforts. [ABSTRACT FROM AUTHOR]

Mytilus species are important organisms in marine systems being highly abundant and widely distributed along the coast of Europe and worldwide. They are typically used in biological effects studies and have a suite of biological effects endpoints that are frequently measured and evaluated for stress effects in laboratory experiments and field monitoring programmes. Differences in bioaccumulation and biological responses of the three Mytilus species following exposure to copper (Cu) were investigated. A laboratory controlled exposure study was performed with three genetically confirmed Mytilus species; M . galloprovincialis , M . edulis and M . trossulus . Chemical bioaccumulation and biomarkers were assessed in all three Mytilus species following a 4 day and a 21 day exposure to waterborne copper concentrations (0, 10, 100 and 500 μg/L). Differences in copper bioaccumulation were measured after both 4 and 21 days, which suggests some physiological differences between the species. Furthermore, differences in response for some of the biological effects endpoints were also found to occur following exposure. These differences were discussed in relation to either real physiological differences between the species or merely confounding factors relating to the species natural habitat and seasonal cycles. Overall the study demonstrated that differences in chemical bioaccumulation and biomarker responses between the Mytilus spp. occur with potential consequences for mussel exposure studies and biological effects monitoring programmes. Consequently, the study highlights the importance of identifying the correct species when using Mytilus in biological effects studies. [ABSTRACT FROM AUTHOR]

In this study we compared some aspects of the physiology of the invasive blue mussel species Mytilus trossulus and the native Mytilus edulis in the White Sea. We registered the heart activity of M. edulis, M. trossulus and the hybrids in situ for two years and tested their thermal tolerance in a laboratory experiment. In situ monitoring showed that the heart rate, as well as its variability, was greater in the invasive species and the hybrids than in the native mussel species. At the same time, the native species showed a higher thermal tolerance in the laboratory experiment. Our results suggest that, when it comes to adaptation to increased temperature, M. edulis has a greater physiological potential than M. trossulus. In a warming climate, the invasive species may lose in competition with the native one due to a higher level of metabolism. [Display omitted] • Long-term (two years) comparative field studies of the heart activity of two congeneric blue mussels, Mytilus edulis and Mytilus trossulus , were conducted for the first time. • M. trossulus and the hybrids had a lower metabolic rate at summer temperatures. • M. edulis had a higher thermal tolerance. [ABSTRACT FROM AUTHOR]

Benthic suspension feeders have traditionally been considered an important link between pelagic and benthic food webs in shallow seas. Their ecological impact depends highly on the removal rate of pelagic production from the water column. Besides phytoplankton, benthic suspension feeders can feed on microphytobenthos and detritus suspended in the water column by wind-waves or tidal forces. The share of the pelagic component in the diet of benthic suspension feeders is poorly studied in the non-tidal environment. We examined the diatom food items of two bivalve species, Mytilus trossulus Gould and Dreissena polymorpha Pallas, at four shallow locations in the Gulf of Riga basin, in the Baltic Sea, differing in hydrographic characteristics. The share of pennate benthic diatoms was always higher in mussel food than in ambient water, whereas pelagic species were under-represented. Mussels never consumed the dominant genera that were in the water column, Cylindrotheca and Leptocylindrus. There were no differences in the main food source between the two mussel species. Our results suggest that the impact of benthic suspension feeders on pelagic foodwebs and their role in promoting benthic-pelagic coupling is of a minor importance in the study area, whereas the impact on benthic food webs may be mainly by the re-arrangement of energy within benthic pathways. [ABSTRACT FROM AUTHOR]

Bioaccumulation of paralytic shellfish toxins (PSTs) produced by the dinoflagellate Alexandrium ostenfeldii was investigated in the northern Baltic Sea. The study was based on the assumption that the toxins released during high magnitude blooms of A. ostenfeldii will accumulate in the biota at the bloom site, especially in bivalves. To test this, experiments with blue mussels ( Mytilus trossulus) exposed to toxic A. ostenfeldii in field conditions were carried out together with a field survey aimed to quantify natural distribution of PSTs in the biota. As hypothesized, PSTs accumulated in the tissues of the blue mussels during the incubations. Toxins were also detected in natural bivalve communities at the bloom site, the highest toxin concentrations found in the small Cerastoderma glaucum individuals, exceeding the EC safety limit for shellfish consumption. Relatively high total toxin concentrations were also detected from fish ( Perca fluviatilis). These are the first records of PST transfer in the food web of the northern Baltic Sea. [ABSTRACT FROM AUTHOR]

Highlights: [•] Neoplastic M. trossulus haemocytes displayed a wide range of aneuploidy levels from 1.4n to 5.5n. [•] There was no correlation between aneuploidy and neoplasia progression for transitional stages of the disease. [•] Several cell populations with differing ploidy were observed in transitional samples. [•] Normal haemocytes had ploidy levels from 1.7n to 2.7n. [•] Some highly leukemic samples had normal ∼2n ploidy and no aneuploidy. [Copyright &y& Elsevier]

Abstract: Blue mussels (Mytilus trossulus) were transplanted in cages for three months in two Swedish coastal areas in the Bothnian Sea (northern Baltic Sea) to investigate the interactions between analysed environmental chemicals and biological responses. A wide array of biological parameters (biomarkers) including antioxidant and biotransformation activity, geno-, cyto- and neurotoxic effects, phagocytosis, bioenergetic status and heart rate were measured to detect the possible effects of contaminants. Integrated Biomarker Response index and Principal Component Analysis performed on the individual biological response data were able to discriminate between the two study areas as well as the contaminated sites from their respective local reference sites. The two contaminated sites outside the cities of Sundsvall (station S1) and Gävle (station G1) were characterised by different biomarker response patterns. Mussels at station S1 showed a low condition index, increased heart rate recovery time and phagocytosis activity coinciding with the highest tissue concentrations of some trace metals, polycyclic aromatic hydrocarbons and organotins. At station G1 the highest organochlorine pesticide concentration was recorded as well as elevations in glutathione S-transferase activity, thiamine content and low lysosomal membrane stability. Significant variability in the geno- and cytotoxic responses and bioenergetic status was also observed at the different caging stations. The results obtained suggest that different chemical mixtures present in the study areas cause variable biological response patterns in organisms. [Copyright &y& Elsevier]

Three nuclear DNA markers that diagnostically differentiate mussels within the Mytilus edulis complex (M. edulis, M. trossulus and M. galloprovincialis) are commonly used in taxonomic investigations: Glu5', ITS and EFbis. As a rule, DNA extraction is performed before amplification. It is a time consuming process in the case of traditional methods based on chloroform and phenol extraction or relatively expensive using kits with ready spin columns. Moreover, DNA isolation from larvae is problematic, because of the small amount of tissue available. In this report we describe a simple, fast and inexpensive method of DNA extraction and gene amplification from larvae, spat and adults of the Baltic mussel Mytilus trossulus. The extraction method is adapted from that of Wang et al. (2006) and is based on digestion of tissue or whole animals in STE solution and direct gene amplification. On the basis of the results of routine analyses of mussels carried out in our laboratory we have concluded that the method we propose gives results that are consistent with standard methods, without requiring expensive reagents/equipment and is time saving. [ABSTRACT FROM AUTHOR]

The doubly uniparental inheritance system allows for the use of two independent mitochondrial genomes for population history investigations. Under this system, two lineages of mitochondrial DNA (mtDNA) exist and males are typically heteroplasmic, having the additional, usually divergent, mitochondrial genome inherited from their male parent. This additional mtDNA typically evolves faster, potentially allowing for insight into more recent events in population history. Few studies did explore this possibility in marine mussels Mytilus showing its usefulness. Recent observations of the Mytilus trossulus mussels who have retained their native mtDNA in European waters posed the question of their origin. Are they part of a population present, but previously undetected, or is this a potentially human mediated, ongoing spread of an invasive species? To tackle this question, we amplified with species-specific primers and sequenced an approximately 1,200-bp-long fragment spanning COIII and ND2 genes from both mitochondrial genomes of mussels sampled at five locations worldwide, covering the whole M. trossulus range. The overall pattern of polymorphisms is compatible with the entirely postglacial history of the whole species, indicating a very deep bottleneck at last glacial maximum, with possible retention of the whole species in a single refugium, and the effective population size of no more than a few thousands. Both analyses of molecular variance and isolation with migration (IM) models point at the West Atlantic as the source of the European M. trossulus mussels, at least the ones who retained their native mtDNA. The hypothesis that this is an ongoing, human-mediated process was considered. To this end, comparison with the well-known case: the introduction of congeneric mussel, Mytilus galloprovincialis, from Mediterranean Sea to Asia was used. This introduction occurred within the last 100 years. The results inferred by the IM model suggest that the timing and structure of transatlantic migration of M. trossulus differs significantly from the M. galloprovincialis case: it is more than 1,000 years old and involves a much larger fraction of the ancestral population. Therefore, most likely, this invasion is not a human-mediated process. [ABSTRACT FROM AUTHOR]

This study focused on the bioaccumulation intensities of the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride (bmimCl) by two invertebrates: Mytilus trossulus and Balanus improvisus and the green alga Chlorella vulgaris. The bioconcentration of bmimCl by two invertebrates was tested in the contaminated water, both with and without the presence of green algae previously exposed to the bmimCl. The experimentally obtained bioconcentration factors (BCFs) are quite low and do not exceed the value of 10. The presence of contaminated C. vulgaris in the water induces an increase in BCF of barnacles up to 80% in comparison to barnacles exposed only to contaminated water. Detoxication of M. trossulus may be more effective in the presence of higher IL concentrations. BCFs for hard tissues of the mussel indicates an exclusively physical sorption mechanism on the mineral surface. [ABSTRACT FROM AUTHOR]

Closely related species with different physiological tolerances and distributions make ideal systems for documenting range shifts in response to a changing climate. Mytilus edulis, M. trossulus, and M. galloprovincialis are sibling species of marine mussels with distinct biogeographical ranges that are correlated with sea surface temperatures. We determined the scope for growth of these three species at a range of temperatures to determine if energetics could predict their distributions. Scope for growth (SFG) represents energy available for growth and/or reproduction above that necessary for maintenance requirements. The SFG of M. galloprovincialis, the species known to inhabit the warmest habitats, was shifted towards warmer temperatures compared to the other two species, remaining positive until nearly 30 °C. M. edulis, a cold-temperate species, maintained a positive SFG up to 23 °C. M. trossulus, a boreal species, generally was not able to maintain a positive SFG above 17 °C. The warm end of each species' range correlated strongly with the point at which that species' SFG became negative in summer and fall. Energetics at cold temperatures did not predict the cold end of the species' ranges, as there was no clear SFG advantage to explain the dominance of M. trossulus in cold habitats. As sea surface temperatures continue to warm with climate change, the energetics of these three species provide a basis for developing mechanistic models predicting future distribution and productivity changes in mussel populations. [ABSTRACT FROM AUTHOR]

Abstract: Sediment from four southern Baltic Sea locations and caged mussels were analyzed for PCBs, organochlorine pesticides and metals (Cu, Zn, Cd, Pb, Hg). In mussels, which were additionally analyzed for 16 individual PAHs, a set of biomarker responses was measured to derive an integrated biomarker response (IBR) index as a part of integrative assessment of pollution in this area. Concentrations of PCBs, ΣDDT, and metals in sediment and mussels, greatest within the Gulf of Gdańsk area, showed decreasing gradients outwards from the Gulf. Sediment quality quotients (SQQs) and biological impact quotients (BIQs), reflecting on sediment- and mussel-accumulated contaminants'' potential for biological effects, respectively, pointed out to the Gulf of Gdańsk to be of greatest concern among the examined sites. The IBRs corresponded poorly with the SQQs and BIQs, nevertheless, provided a line of evidence indicative of biological effects of contaminants to support more complex processes of environmental status assessment. [Copyright &y& Elsevier]

Coping with environmental stress may involve combinations of behavioral and physiological responses. We examined potential interactions between adult mussels' simple behavioral repertoire – opening/closing of the shell valves – and thermal stress physiology in common-gardened individuals of three Mytilus congeners found on the West Coast of North America: two native species (M. californianus and M. trossulus) and one invasive species from the Mediterranean (M. galloprovincialis). We first continuously monitored valve behavior over three consecutive days on which body temperatures were gradually increased, either in air or in seawater. A temperature threshold effect was evident between 25 and 33°C in several behavioral measures. Mussels tended to spend much less time with the valves in a sealed position following exposure to 33°C body temperature, especially when exposed in air. This behavior could not be explained by decreases in adductor muscle glycogen (stores of this metabolic fuel actually increased in some scenarios), impacts of forced valve sealing on long-term survival (none observed in a second experiment), or loss of contractile function in the adductor muscles (individuals exhibited as many or more valve adduction movements following elevated body temperature compared with controls). We hypothesize that this reduced propensity to seal the valves following thermal extremes represents avoidance of hypoxia–reoxygenation cycles and concomitant oxidative stress. We further conjecture that prolonged valve gaping following episodes of elevated body temperature may have important ecological consequences by affecting species interactions. We then examined survival over a 90 day period following exposure to elevated body temperature and/or emersion, observing ongoing mortality throughout this monitoring period. Survival varied significantly among species (M. trossulus had the lowest survival) and among experimental contexts (survival was lowest after experiencing elevated body temperature in seawater). Surprisingly, we observed no cumulative impact on survival of 3 days relative to 1 day of exposure to elevated body temperature. The delayed mortality and context-specific outcomes we observed have important implications for the design of future experiments and for interpretation of field distribution patterns of these species. Ultimately, variation in the catalog of physiological and behavioral capacities among closely related or sympatric species is likely to complicate prediction of the ecological consequences of global change and species invasions. [ABSTRACT FROM AUTHOR]

Abstract: Baltic Sea blue mussels (Mytilus trossulus) were used as sentinel organisms to detect the biological effects of chemical contamination in the low salinity environment. Mussels naturally adapted to a salinity of ca. 6.0PSU were caged for 30days at four sites along an assumed pollution gradient (salinity ca. 4.5PSU) in the vicinity of Finland''s largest oil refinery and harbor Kilpilahti in the Gulf of Finland. Tissue concentrations and accumulation rates of especially organic contaminants (PAHs, PCBs and organotins) were clearly elevated at the innermost coastal stations near the harbor area. Biological effects of contaminant exposure on caged mussels were evaluated by measuring a suite of biomarkers including catalase, glutathione S-transferase, superoxide dismutase, glutathione reductase, lipid peroxidation, acetylcholinesterase activity and lysosomal membrane stability. Mussels transplanted near the harbor area were able to elevate their antioxidant defense in response to environmental contamination. Reduced morphometric condition index and soft tissue growth rate together with increased lipid peroxidation and low lysosomal membrane stability were also observed at the most contaminated site. The results suggest that caging of M. trossulus for four weeks at lower salinity is a feasible method for the detection of environmental pollution also in low salinity areas of the Baltic Sea. [Copyright &y& Elsevier]

Lectin (MTL) of molecular weight 16,492 Da and pI 6.09 ± 0.01 that was most active in the pH range 9.0-10.0, was thermally labile, and did not require Ca for activation was isolated from the mussel Mytilus trossulus. The MTL was a Gal/GalNAc-specific lectin that exhibited an affinity for glycoproteins containing mucin-type chains. The cross reactivity between MTL and a lectin isolated from the mussel Crenomytilus grayanus was determined. It was shown that MTL at high concentration stimulated expression of TNF-α and IFN-γ; at low concentration, exhibited immunomodulating activity by reducing hyperexpression of cytokine IL-10. [ABSTRACT FROM AUTHOR]

Climate change is affecting species' physiology, pushing environmental tolerance limits and shifting distribution ranges. In addition to temperature and ocean acidification, increasing levels of hyposaline stress due to extreme precipitation events and freshwater runoff may be driving some of the reported recent range shifts in marine organisms. Using two-dimensional gel electrophoresis and tandem mass spectrometry, we characterized the proteomic responses of the cold-adapted blue mussel Mytilus trossulus, a native to the Pacific coast of North America, and the warm-adapted M. galloprovincialis, a Mediterranean invader that has replaced the native from the southern part of its range, but may be limited from expanding north due to hyposaline stress. After exposing laboratory-acclimated mussels for 4h to two different experimental treatments of hyposaline conditions and one control treatment (24.5, 29.8 and 35.0 psu, respectively) followed by a 0 and 24h recovery at ambient salinity (35psu), we detected changes in the abundance of molecular chaperones of the endoplasmic reticulum (ER), indicating protein unfolding, during stress exposure. Other common responses included changes in small GTPases of the Ras superfamily during recovery, which suggests a role for vesicle transport, and cytoskeletal adjustments associated with cell volume, as indicated by cytoskeletal elements such as actin, tubulin, intermediate filaments and several actin-binding regulatory proteins. Changes of proteins involved in energy metabolism and scavenging of reactive oxygen species suggest a reduction in overall energy metabolism during recovery. Principal component analyses of protein abundances suggest that M. trossulus is able to respond to a greater hyposaline challenge (24.5 psu) than M. galloprovincialis (29.8 psu), as shown by changing abundances of proteins involved in protein chaperoning, vesicle transport, cytoskeletal adjustments by actin-regulatory proteins, energy metabolism and oxidative stress. While proteins involved in energy metabolism were lower In M. trossulus during recovery from hyposaline stress, M. galloprovincialis showed higher abundances of those proteins at 29.8 psu, suggesting an energetic constraint in the invader but not the native congener. Both species showed lower levels of oxidative stress proteins during recovery. In addition, oxidative stress proteins associated with protein synthesis and folding in the ER showed lower levels during recovery in M. galloprovincialis, in parallel with ER chaperones, indicating a reduction in protein synthesis. These differences may enable the native M. trossulus to cope with greater hyposaline stress in the northern part of its range, as well as to outcompete M. galloprovincialis in the southern part of M. trossulus1 range, thereby preventing M. galloprovincialis from expanding further north. [ABSTRACT FROM AUTHOR]

Abstract: We measured the concentrations and chemical structures of persistent organochlorines (OCs) in blue mussels (Mytilus trossulus) from 44 sites across southwest and southeast Alaska in an effort to determine both the sources of these compounds and the extent to which this region might be contaminated. High PCB concentrations were detected at Amchitka, Adak, and Unalaska Islands (83, 430, and 2800μgkg−1 dry weight, respectively) in the Aleutians with relatively low concentrations elsewhere (7.1–51μgkg−1 dry weight). Heavy PCB congener profiles (indicative of localized point sources) characterized the high concentration sites whereas distinctly lighter congener profiles (indicative of atmospheric transport) characterized the lower concentration sites. Elevated PCB concentrations at Adak were restricted to a small area along the island’s eastern shore, suggesting either limited dispersion or rapid dilution of these compounds. More uniform chlorinated pesticide concentrations among the collection sites suggests that these compounds are entering the Aleutian ecosystem from distant sources. Pesticide concentrations correlated significantly with seabird density across the islands we sampled, thus identifying biological transport as a delivery mechanism of these compounds to the Aleutian archipelago. Our findings do not implicate persistent organochlorines as a significant factor in the recent pinniped and sea otter population declines across southwest Alaska. [Copyright &y& Elsevier]

The ability to acclimate to variable environmental conditions affects the biogeographic range of species, their success at colonizing new habitats, and their likelihood of surviving rapid anthropogenic climate change. Here we compared responses to temperature acclimation (4weeks at 7, 13 and 19°C) in gill tissue of the warm-adapted intertidal blue mussel Mytilus gaUoprovincialis, an invasive species In the northeastern Pacific, and the cold-adapted M. trossulus, the native congener In the region, to better understand the physiological differences underlying the ongoing competition. Using two-dimensional gel electrophoresis and tandem mass spectrometry, we showed that warm acclimation caused changes in cytoskeletal composition and proteins of energy metabolism in both species, consistent with increasing rates of filtration and respiration due to increased ciliary activity. During cold acclimation, changes in cytoskeletal proteins were accompanied by increasing abundances of oxidative stress proteins and molecular chaperones, possibly because of the increased production of aldehydes as Indicated by the upregulation of aldehyde dehydrogenase. The cold-adapted M. trossulus showed Increased abundances of molecular chaperones at 19°C, but M. gaUoprovincialis did not, suggesting that the two species differ in their long-term upper thermal limits. In contrast, the warm-adapted M. gaUoprovincialis showed a stronger response to cold acclimation than M. trossulus, including changes in abundance in more proteins and differing protein expression profiles between 7 and 13°C, a pattern absent in M. trossulus. In general, increasing levels of oxidative stress proteins inversely correlate with modifications in Krebs cycle and electron transport chain proteins, indicating a trade-off between oxidative stress resistance and energy production. Overall, our results help explain why M. gaUoprovincialis has replaced M. trossulus In southern California over the last century, but also suggest that M. trossulus may maintain a competitive advantage at colder temperatures. Anthropogenic global warming may reinforce the advantage M. gaUoprovincialis has over M. trossulus in the warmer parts of the latter's historical range. [ABSTRACT FROM AUTHOR]

The blue mussels Mytilus edulis and Mytilus trossulus occur sympatrically and are able to hybridize in populations on the eastern coast of Newfoundland, Canada, presenting an opportunity to study their aggregational behavior. Aggregation behavior may therefore provide insight into post-settlement interactions and pre-zygotic reproductive isolation between the species. Three treatments were designed using M. edulis and M. trossulus to investigate their intraspecific and interspecific spatial distribution patterns. With Ripley's K-function and Monte Carlo simulation analysis, we found that in the single-species treatment, M. edulis aggregated significantly but not M. trossulus. Based on results of two-way ANOVAs, both the number of aggregations and the moving distance were significantly affected by the treatments (single-species or mixed-species treatment) and times (24, 48, 72 and 96 h). In further pairwise comparisons using Tukey's test, M. edulis aggregated differently with or without M. trossulus occupying the same tank, suggesting that the aggregational behavior of M. edulis could be driven by species-specific chemical cues. The result that M. edulis aggregates intraspecifically may increase the probability of intraspecific fertilization of the spawned gametes and thus function as a pre-zygotic reproductive isolation mechanism maintaining the blue mussel hybrid zone. [ABSTRACT FROM AUTHOR]