Mussel Larvae Research Articles

Early and efficient induction of antioxidant defense system in Mytilus galloprovincialis embryos exposed to metals and heat stress

The present study aims to elucidate the stress response of early life stages of Mytilus galloprovincialis to the combine effects of selected metals and elevated temperature.For this purpose, we investigated the response of a large panel of oxidative stress markers such as catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) activities and lipid peroxidation (thiobarbituric acid reactive substrates (TBARS) concentration) and metallothionein accumulation (MT) as well as selected gene transcription level and metal accumulation in mussels larvae exposed to a sub-lethal concentration of Cu (9.54µg/L), Ag (2.55µg/L) and mixture of the two metals (Cu (6.67µg/L)+Ag (1.47µg/L)) along with a temperature gradient (18, 20 and 22°C) for 48h.Cu and Ag applied as single or mixture were differentially accumulated in mussel larvae according to the exposure temperature. Sod, cat, gst and mt-10 gene transcription levels showed an important increase in larvae exposed to Cu, Ag or to the mix compared to the control condition at 18°C. The same pattern but with higher induction levels was recorded in larvae co-exposed to metals at 20°C. At 22°C, a significant decrease in mRNA abundance of cat, gst and sod and a significant up-regulation of mts targets (mt10 and mt20) were observed. Resultssuggest that co-exposure to metals and moderate elevated temperature (20 and 22°C) significantly increased the antioxidant enzyme activities of catalase (CAT), and glutathione-S-transferase (GST) and caused an increase of metal and metallothionein concentrations. In contrast, no significant change in lipid peroxidation products measured as TBARS content was observed indicating a protective response of anti-oxidative system.This study provides first evidences of the early and efficient protective response of antioxidant defense mechanisms in mussel's early life stages facing in multi stressors situations.

Composition of Juvenile Corals on Different Morphotypes of Substrate at Karimunjawa Archipelago, Indonesia

Rapid developments of industry and population growth have lead to ecological pressures on coastal areas. Semarang as capital of Central Java and port city, has an environment sensitivity which is important to be investigated. Sediment is an important part in aquatic environment because acts as sink or source of pollutant and could be used to assess coastal environment health. Three locations had been studied, i.e. Tanjung Mas Port, estuaries of Banjirkanal Barat and Banjirkanal Timur. These locations were compared to assess their health of sediment through elutriate sediment toxicity test. Eighteen grams of sediment from each locations were weighed and placed in 1 L Beaker glass. Eggs and sperm are taken from spawning of adult green mussel in laboratory. Thirty mL of sperm was added to the eggs and fertilized eggs were observed microscopically. Fertilized eggs were exposure to elutriate water-sediment from each location for 48 hour. Statistical analysis showed that there are significantly different abnormalities larvae percentage of sites 5, 8 and 13. The highest percentage of abnormality larvae occurred in Port Tanjung Mas, followed by Banjirkanal Timur and Banjirkanal Barat. Lead concentrations in sediments of coastal Semarang was ranged from 10.9 to 15.62 mg.kg -1 , with an average of 13.69 mg.kg -1 . Lead concentration was decreased form Port, Banjirkanal Timur and Banjirkanal, respectively. The abnormalities of green mussel larva may related to lead contamination. It could be concluded that sediment quality in Port area was very poor compare than other site. Keywords: bioassay , green mussel larvae, sediment, Semarang coastal area

Sole and Combined Usage of Ultra-sonication and Hydrogen Peroxide as Mitigation Techniques of Bio-fouling

Mussels are stubborn organism attached to solid substrate by byssus threads and caused operational problems in utility of power generating stations. Sole and combined usage of ultrasonic (28 kHz- and 42 kHz- frequencies) and hydrogen peroxide (H2O2) has studied for control of blue mussel larvae and adult stage in seawater condition. A theoretical wo rking model using disinfection (Chick and Watson type) approaches is presented based on helpful results of experiments. This study also demonstrate that the combined treatment (ultra-sonication with H2O2) is overall highly efficient than individual treatment would, but on the basis of exposure time, the ultra-sonication was the most efficient among them. Therefore the development of sole and combined technique might be effective practical mitigation strategy against mussel attachment for water handling facilities.

Effects on larval metamorphosis in the musselMytilus coruscusof compounds that act on downstream effectors of G-protein-coupled receptors

The metamorphic responses of mussel (Mytilus coruscus) larvae to pharmacological agents affecting G proteins and the adenylate cyclase/cyclic AMP (AC/cAMP) pathway were examined in the laboratory. The G protein activators guanosine 5′-[β,γ-imido]triphosphate trisodium salt hydrate and guanosine 5′-[γ-thio]triphosphate tetralithium salt only induced larval metamorphosis in continuous exposure assays, and the G protein inhibitor guanosine 5′-[β-thio]diphosphate trilithium salt did not exhibit inducing activity. The non-specific phosphodiesterase inhibitor theophylline and the cAMP-specific phosphodiesterase IV inhibitor 4-(3-Butoxy-4-methoxybenzyl)imidazolidin-2-one exhibited inducing activity, while the non-specific phosphodiesterase inhibitor 3-Isobutyl-1-methylxanthine only showed inducing activity at 10−4M in continuous exposure assays. The cyclic nucleotide analogue N6,2′-O-Dibutyryladenosine 3′,5′-cyclic monophosphate sodium salt did not exhibit significant inducing activity. Both the adenylate cyclase activator forskolin and the adenylate cyclase inhibitor nitroimidazole exhibited inducing activity at 10−4to 10−3M concentrations in continuous exposure assays. Among these tested agents, the adenylate cyclase inhibitor (±)-miconazole nitrate salt showed the most promising inducing effect. The present results indicate that G protein-coupled receptors and signal transduction by AC/cAMP pathway could mediate metamorphosis of larvae in this species.

Validation of trophic and anthropic underwater noise as settlement trigger in blue mussels.

Like the majority of benthic invertebrates, the blue mussel Mytilus edulis has a bentho-pelagic cycle with its larval settlement being a complex phenomenon involving numerous factors. Among these factors, underwater noise and pelagic trophic conditions have been weakly studied in previous researches. Under laboratory conditions, we tested the hypothesis that picoplankton assimilation by the pediveliger blue mussel larvae acts as a food cue that interacts with anthropic underwater sound to stimulate settlement. We used 13C-labeling microalgae to validate the assimilation of different picoplankton species in the tissues of pediveliger larvae. Our results clearly confirm our hypothesis with a significant synergic effect of these two factors. However, only the picoeukaryotes strains assimilated by larvae stimulated the settlement, whereas the non-ingested picocyanobacteria did not. Similar positive responses were observed with underwater sound characterized by low frequency vessel noises. The combination of both factors (trophic and vessel noise) drastically increased the mussel settlement by an order of 4 compared to the control (without picoplankton and noise). Settlement levels ranged from 16.5 to 67% in 67 h.

High sensitivity of embryo-larval stage of the Mediterranean mussel, Mytilus galloprovincialis to metal pollution in combination with temperature increase

The present work aimed to assess the effects of two widespread metallic pollutants, copper and silver, along with environmentally-realistic temperature increases, on embryo-larval development of the Mediterranean mussel Mytilus galloprovincialis. First, mussel embryos upon fertilization were exposed for 48 h to increasing concentrations of Cu (0.5–500 μg/L) and Ag (0.1–100 μg/L) at different temperatures (18, 20, 22 or 24 °C) in order to characterize toxicity of each toxicant at the different tested temperatures. Increasing concentrations of a Cu-Ag mixture were then tested in order to assess the mixture effect at different temperatures (18, 20 or 22 °C). Embryotoxicity was measured after 48 h of exposure (D-larvae stage) considering both the percentage of abnormalities and developmental arrest in D-larvae. The results suggest that the optimum temperature for mussel larvae development is 18 °C (12.65± 1.6% malformations) and beyond 20 °C a steep increase of abnormal larvae was observed up to 100% at 24 °C. Ag was more toxic than Cu with a 50% effective concentration (EC50) at 18 °C of 6.58 μg/L and 17.6 μg/L, respectively. Temperature increased the toxicity of both metals as proved with the EC50 at 20 °C at 3.86 μg/L and 16.28 μg/L for Ag and Cu respectively. Toxic unit calculation suggests additive effects of Cu and Ag in mixture at 18 and 20 °C. These results highlight a possible impairment of M. galloprovincialis reproduction in the Mediterranean Sea in relation to increase of both pollutants and water temperature due to global warming.

Diel vertical migration and cross-shore distribution of barnacle and bivalve larvae in the central Chile inner-shelf

The vertical and horizontal distribution of larval stages of the most common intertidal barnacle and mussel species were characterized in near-shore waters of central Chile. Paired day/night cruises were conducted on four spring-summer dates between December 2007 and November 2008, under contrasting wind, wave height, and near-shore stratification conditions. Regardless of variability in oceanographic conditions, the highest abundances of barnacle and mussel larvae were found within 1500m from shore. Non-uniform vertical distributions were observed for chthamalids, balanids and mussel larvae, but patterns of diel variability differed among them. Chthamalid and balanid nauplii, as well as balanid cyprids were more abundant in the upper 20m of the water column, while the density of chthamalid cyprids was highest near the bottom. Mussel larvae were only found within 20m of the surface. The Mean Depth Distribution (MDD) of all nauplii (balanid and chthamalid) and chthamalid cyprids was deeper during day than night, suggesting typical diel vertical migration (DVM), but this difference was statistically significant only for nauplii. Mussels did not show diel differences in vertical distribution. The amplitude of DVM, measured as the difference between daytime and nighttime MDD, decreased with increasing wave height in chthamalid and balanid nauplii, but not with along-shore wind stress. Chthamalid nauplii, and to a lesser extent, balanid nauplii were found below the pycnocline during the day and above at night, suggesting that DVM involves daily crossing of this density barrier. In contrast, cyprids of all barnacle species were distributed across the pycnocline with no clear pattern. The results suggest that barnacle and bivalve larvae may exhibit a variety of behavioral responses to position themselves in the water column despite typically turbulent near-shore waters, and that such behavior varies between species and through ontogeny within species. Moreover, some stages of barnacle larvae perform DVM, but the amplitude decreased with increasing wave height – which may be either a plastic response to environmental cues or merely turbulent mixing impeding the ability of larvae to perform vertical migration.

Stress-induced variation in host susceptibility to parasitic freshwater mussel larvae

An increasing number of studies demonstrate the critical role of the host–parasite relationship for the persistence and distribution of freshwater mussels. Laboratory experiments are a powerful tool for quantifying the physiological compatibility between parasitic mussel larvae and fish hosts and are clearly applicable to species conservation. Recent findings, however, indicate potential need to control for biases caused by infection intensity and host stress responses. We tested glochidia metamorphosis success and host plasma cortisol response using Lampsilis siliquoidea glochidia on Lepomis macrochirus. The main aims were to (1) compare metamorphosis success in response to infection intensity (number of attached glochidia per fish) and (2) compare metamorphosis success between typical and reduced-stress approaches to the handling and infection of host fish. We found no effect of the glochidia bath density used to infect the fish (1000–4000–8000 glochidia l−1) or the resulting infection intensity on metamorphosis success, although host plasma cortisol was correlated with infection intensity at 24 h post infection. Small but statistically significant differences in metamorphosis success were observed between the typical and reduced-stress approaches. Overall, typical host compatibility testing methods appear to be robust to these variables, but more emphasis on standardizing laboratory protocols may provide more repeatable data.

Wandering mussels: using natural tags to identify connectivity patterns among Marine Protected Areas

Knowledge of connectivity pathways in the marine environment is crucial for understanding the spatial structure of populations and for developing appropriate monitoring and management strategies. Here, we used the mussel Mytilus galloprovincialis as a model species to investigate connectivity patterns within the Berlengas and Arrabida Marine Protected Areas (MPAs) along the central Portuguese west coast. We generated an atlas of location-specific environmental markers based on the microchemistry of bivalve larval shells (using laser ablation inductively coupled plasma mass spectrometry). This atlas was then employed to trace the natal origins of newly settled mussels and generate connectivity matrices among populations. Our results reflected 3 distinctive chemical signatures in larval shells, corresponding to 3 regions: Estremadura, Cascais and Arrabida. Linear discriminant analyses allowed for a high reclassification success (average of 79.5% of jackknifed cross-validated cases correctly assigned) based on 8 of the 16 trace elements analyzed (B, P, Co, Cu, Zn, Ce, Pb and U). The population connectivity matrix identified different dispersal pathways for mussel larvae, in particular a predominantly northward dispersion pattern in July 2013. This pattern was consistent with simultaneous environmental physical data, which confirmed an extended period of wind reversal and upwelling relaxation. The Arrabida MPA was an important source population for the other 2 regions and showed high rates of self-recruitment but limited connectivity to the Berlengas MPA. These direct measures of demographic connectivity can be a powerful tool to inform policymakers on the conservation and management of ecologically coherent networks of protected areas in coastal marine ecosystems.

Response of competent blue mussel (Mytilus edulis) larvae to positive and negative settlement cues

Recent work on larval settlement cues has emphasized mechanisms by which larvae exploit individual, positive cues (cues that larvae move toward), often in complex flow fields. Yet in natural systems, larvae of habitat generalists probably respond to multiple settlement cues, including a mixture of positive and negative cues. First, a simple test chamber in which cue dispersal was dominated by diffusion was used to assess whether competent blue mussel (Mytilus edulis) larvae responded negatively or positively to cues from a variety of intertidal species. Second, choice experiments tested the responses of larvae offered a mixture of conflicting (positive and negative) cues from the same direction and conflicting cues from different directions. Responses to individual cues were predictable from established ecological interactions. Larvae were attracted to odors from conspecifics, tended to move toward odors from a filamentous alga, avoided odors from two predators of post-settlement mussels, and exhibited little response to odors from an herbivorous gastropod. Negative and positive cues offered from the same direction produced movement both toward and away from the mixture, while offering the combined cues from different directions resulted in net movement that was largely consistent with predictions from the individual cue responses. Larvae presented with a choice between two negative cues mainly remained where they started, in the middle of the test apparatus, and exhibited no choice. These results highlight the need to consider the combined effects of a broad range of cues when evaluating the net effect of cues on settlement in the field.

Ecological Assessment in Semarang Coastal Area Based on Sediment Bioassay Approach

Rapid development of industry and population growth leads to ecological pressures on coastal areas. Semarang as the capital of Central Java and as a port city has a sensitivity of environment which is important to do. Sediment is an important thing from aquatic environment because acts as sink or source of pollutant and could be used to assess health of coastal environment. Three locations that had been studied were Tanjung Mas Port, estuaries of West Canal Flood and estuaries of East Canal Flood. These locations were compared to assess health of sediment through elutriate - sediment toxicity test. Sediment from each location was exposure to green mussel larvae for 48 hour. Statistical analysis with ANOVA showed that abnormality larvae from sites 5, 8 and 13 are significantly different from other. The highest of abnormality larvae occurred in Port, followed by Eastern Canal Flood and Western Canal Flood. From other study had been reported that Ammonia beccari, bio indicator for hypoxia/anoxia/eutrophic was found in Port. Lead was decreased form Port, East Canal Flood and West Canal Flood, respectively. So, we concluded that sediment quality from Port, West Canal Flood and East Canal Flood are decreased.

Maintained larval growth in mussel larvae exposed to acidified under-saturated seawater.

Ocean acidification (OA) is known to affect bivalve early life-stages. We tested responses of blue mussel larvae to a wide range of pH in order to identify their tolerance threshold. Our results confirmed that decreasing seawater pH and decreasing saturation state increases larval mortality rate and the percentage of abnormally developing larvae. Virtually no larvae reared at average pHT 7.16 were able to feed or reach the D-shell stage and their development appeared to be arrested at the trochophore stage. However larvae were capable of reaching the D-shell stage under milder acidification (pHT ≈ 7.35, 7.6, 7.85) including in under-saturated seawater with Ωa as low as 0.54 ± 0.01 (mean ± s. e. m.), with a tipping point for normal development identified at pHT 7.765. Additionally growth rate of normally developing larvae was not affected by lower pHT despite potential increased energy costs associated with compensatory calcification in response to increased shell dissolution. Overall, our results on OA impacts on mussel larvae suggest an average pHT of 7.16 is beyond their physiological tolerance threshold and indicate a shift in energy allocation towards growth in some individuals revealing potential OA resilience.

Family effects on the growth and survival of congeneric blue mussel larvae (Mytilus edulis and M. trossulus)

Intraspecific genetic variation is widely recognized to affect how bivalve larvae respond to variation in environmental conditions, but has been largely ignored in comparisons of larval performance between closely related sibling species. Replicates of five different full-sib families of larval blue mussels (Mytilus edulis and its more northerly congener, M. trossulus) were reared under different temperature (10, 13, and 17 °C) and food conditions in a full factorial design. Growth and survival were strongly affected by temperature, family, the interaction of family and temperature, and the three-way interaction of family, temperature, and food. Family means for days to 20 % survival ranged from 10.2 to 20.0 and did not cluster by species. The two M. trossulus families were intermediate in survival and ranked first and third for growth. The temperature by family interaction effect for survival was very strong, and the two M. trossulus families responded very differently to temperature manipulations. One M. trossulus family exhibited highest survival at 13 °C, while the other M. trossulus family and all three M. edulis families exhibited highest survival at 10 °C. By contrast, greatest growth consistently occurred at 17 °C, indicating that higher mortality in warmer water may be at least partially offset (at a population level) by more rapid growth in body size. The results illustrate the importance of assaying both growth and survival when evaluating environmental effects on larvae and the need to ensure a high level of genetic diversity when pools of larvae are used to study genetically similar species.

Limnoperna fortunei Dunker, 1857 larvae in different environments of a Neotropical floodplain: relationships of abiotic variables and phytoplankton with different stages of development.

Limnoperna fortunei Dunker, 1857 is an Asian invasive freshwater bivalve. Although there need to contain their spread, studies about the biology of the larvae are scarce. We correlated the larval stages of L. fortunei with biotic factors such as phytoplankton and main abiotic variables in lotic environments of the Upper Paraná River floodplain. The four samples were taken quarterly during the year 2012. The Principal component analysis (PCA) showed only spatial differences, as did a Canonical Correspondence Analysis (CCA). High densities of larvae were recorded in all samples the Paraná River and Baía River only in December, especially those in their initial stage. In the biovolume of Class of algae, Bacillarophyceae showed the highest value, but Chlorophycea who was strongly correlated with the density of D-stage larvae. The large variety of phytoplankton, especially microplankton Chlorophyceae, high values of PO4, NH4 and temperature were positively correlated with high densities of D-stage larvae. We conclude that high temperature, and food availability, indicated by phytoplankton community, favored the reproduction of L. fortunei and enhance the ability of specie dispersion due to the increase in the emission of propagules. Therefore, studies that address the biology of golden mussel larvae should be performed in order to prevent its spread.

Assessing variability in chemical acute toxicity of unionid mussels: Influence of intra- and interlaboratory testing, life stage, and species.

The authors developed a toxicity database for unionid mussels to examine the extent of intra- and interlaboratory variability in acute toxicity tests with mussel larvae (glochidia) and juveniles; the extent of differential sensitivity of the 2 life stages; and the variation in sensitivity among commonly tested mussels (Lampsilis siliquoidea, Utterbackia imbecillis, and Villosa iris), commonly tested cladocerans (Daphnia magna and Ceriodaphnia dubia), and fish (Oncorhynchus mykiss, Pimephales promelas, and Lepomis macrochirus). The results of these analyses indicate that intralaboratory variability for median effect concentrations (EC50) averaged about 2-fold for both life stages, whereas interlaboratory variability averaged 3.6-fold for juvenile mussels and 6.3-fold for glochidia. The EC50s for juveniles and glochidia were within a factor of 2 of each other for 50% of paired records across chemicals, with juveniles more sensitive than glochidia by more than 2-fold for 33% of the comparisons made between life stages. There was a high concurrence of sensitivity of commonly tested L. siliquoidea, U. imbecillis, and V. iris to that of other mussels. However, this concurrence decreased as the taxonomic distance of the commonly tested cladocerans and fish to mussels increased. The compiled mussel database and determination of data variability will advance risk assessments by including more robust species sensitivity distributions, interspecies correlation estimates, and availability of taxon-specific empirically derived application factors for risk assessment.

Across-shelf distribution of blue mussel larvae in the northern Gulf of Maine: consequences for population connectivity and a species range boundary.

Studies of population connectivity have largely focused on along-shelf, as opposed to across-shelf, processes. We hypothesized that a discontinuity in across-shelf mixing caused by the divergence of the Eastern Maine Coastal Current (EMCC) from shore acts as an ecological barrier to the supply of mussel larvae to the coast. Existing data on the relative abundance of two congeneric blue mussels, Mytilus edulis and M. trossulus, were analysed to quantify the association of M. trossulus with the colder temperature signal of the EMCC and generate larval distribution predictions. We then sampled the across-shelf distribution of larvae along two transects during 2011. Larvae were identified using restriction digests of PCR amplicons from the mitochondrial 16S rDNA. Mytilus edulis larvae were consistently abundant on either the inshore and offshore transect ends, but not homogeneously distributed across the shelf, while M. trossulus larvae were less common throughout the study area. The divergence of the EMCC from shore appears to create a break in the connectivity of M. edulis populations by isolating those inshore of the EMCC from upstream larval sources. Across-shelf transport processes can thus produce connectivity patterns that would not be predicted solely on the basis of along-shelf processes.

Early development of the blue mussel Mytilus edulis (Linnaeus, 1758) cultured in potassium-fortified inland saline water

The low potassium concentration in inland saline water (ISW) restrains the normal development of cultured marine organisms, and thus, possesses challenges for the development of ISW aquaculture. Therefore, assessing the effects of potassium fortification in ISW on the performance of cultured marine species is an important step to determine the feasibility of their culture in ISW. The aim of this research was to investigate the effects of potassium fortification in ISW on the performance of early life stages of the blue mussel Mytilus edulis including fertilised eggs, trochophore, veliger and pediveliger larvae. These stages were reared in five different levels of potassium-fortified ISW, namely 20, 40, 60, 80 and 100% of potassium levels equivalent to the potassium level in ocean water (OW) and two controls namely, ISW at 27ppt (ISW27) and OW at 25ppt (OW25). The results showed that the higher levels of potassium in ISW, particularly with 100% K+ fortification (ISW100K+), invariably improved the survival and size, and reduced the developmental stage interval and deformities of blue mussel larvae. Deformities, such as faulty cell cleavage, abnormal formation of trochophore larvae, protruding mantle in veliger larvae, and indented shell margin in veliger and in pediveliger, were observed when reared in any ISW. However, rearing in ISW did not result in any deformities in settlement larvae. The number of deformities was reduced at higher K+ fortification levels, and there were no deformities in pediveliger larvae reared in ISW100K+ and in OW. These results showed that K+ fortification in ISW improves the performance of the rearing of the larval stages of the blue mussel. Statement of relevanceThis study is the first attempt to culture larval stages of blue mussel Mytilus edulis in potassium-fortified inland saline water. The results have shown that that the larval development is feasible only if ISW is fortified with K+. By initiating larval culture in inland saline water, we expect better results will be reflected by adult stages.

Interannual variability in temporal patterns of Chlorophyll–a and their potential influence on the supply of mussel larvae to inner waters in northern Patagonia (41–44°S)

Environmental forcing of biophysical processes can have deep influences on patterns of supply of planktonic larvae to benthic communities in coastal marine ecosystems. We investigated the role of environmental forcing following a recent interannual decrease in larval supply in the Inner Sea of Chiloé (41–45°S) using direct observations and environmental time series over the period 2003–2014. To examine the temporal structure of larval supply and potential associations with environmental forcing (approximated using satellite chlorophyll-a and sea surface temperature), we used wavelet analysis and lagged correlations to test the hypothesis of an association between larval availability and changes in the seasonal cycle of chlorophyll-a concentration, sea surface temperature, and relevant climate variability (Pacific Decadal Oscillation, El Niño-Southern Oscillation and Southern Annular Mode). Our results indicate that a weakening in the annual cycle of chlorophyll-a concentration and abnormally cold sea surface temperature during 2009–2010 can be related to the observed disruption in larval supply to the Inner Sea of Chiloé starting during the 2010–2011 season. The potential influence of climate variability is further discussed as the spatial extent and temporal persistence observed suggest that other ecological processes might have also been affected, and consequently, we suggest a link to transient large-scale climatic forcing.

The role of waterfowl and fishing gear on zebra mussel larvae dispersal

The zebra mussel, Dreissena polymorpha (Pallas 1771), is an invasive freshwater species with major negative impacts, promoting changes in ecosystem structure and function and also contributing to economic losses. Navigation has been considered the primary vector of dispersion and little importance has been given to alternative natural (waterbirds) and other human vectors. Using an experimental approach under field conditions, we evaluated and compared zebra mussel dispersal potential by fishing gear (waders and keepnets) versus mallard ducks (Anas platyrhynchos), by examining the adherence and survival rate of zebra mussel larvae on each vector. In addition, we evaluated the survival of zebra mussel larvae under desiccating conditions (i.e., a set of controlled temperatures and relative humidities). Larvae adhered to all types of vectors and survived desiccation under both laboratory and field conditions and thus appear able to be dispersed long distances overland by both ducks and fishing gear. Specifically, on a per-event basis, fishing gear has a higher potential to spread zebra mussel larvae than ducks. Survival was three times higher on human vectors and the number of larvae attached to human vectors was over double of that on the ducks. However, our findings demonstrate that natural vectors, like ducks, can contribute to the transport of zebra mussel larvae at a local scale. Nevertheless, since vectors related to human activity presented a higher potential for transport, it is imperative to continue campaigns to raise the awareness of anglers and boaters as well as continue the implementation of legislation to reduce the risk of zebra mussel dispersal.

Effects of sodium chloride exposure on ion regulation in larvae (glochidia) of the freshwater mussel Lampsilis fasciola

The salinization of freshwater can have negative effects on ecosystem health, with heightened effects in salt-sensitive biota such as glochidia, the larvae of freshwater mussels. However, the toxicological mechanism underlying this sensitivity is unknown. Therefore, Lampsilis fasciola glochidia were exposed to NaCl (nominally 0.25 and 1.0g/L) prepared in reconstituted moderately-hard water (control), as well as to a dilution of that water (1:4) with ultrapure reference water (diluted control). Unidirectional Na+ influx (measured with 22Na) was evaluated after 1, 3 and 48h of exposure. In addition, unidirectional Cl− influx (measured with 36Cl), whole-body ion (Cl− and Na+) concentrations, and glochidia viability (measured as the ability to close valves) were assessed after 48h of exposure. Significantly reduced glochidia viability (56%) was observed after exposure to 1.0g/L NaCl. Na+ influx was significantly higher in glochidia exposed to both 0.25 and 1.0g/L NaCl for 1h than in those kept under control conditions. After 3 and 48h of exposure, differences in Na+ influx rate between salt-exposed and control glochidia were generally reduced, indicating that larvae may be able to, at least temporarily, recover their ability to regulate Na+ influx when exposed to elevated NaCl concentration. Compared to the moderately-hard water control, whole-body Na+ and Cl− concentrations were relatively unchanged in glochidia exposed to 0.25g/L NaCl, but were significantly elevated in glochidia exposed to 1.0g/L NaCl and the diluted control. While Na+ influx rate had recovered to the control level after 48h of exposure to 1.0g/L NaCl, Cl− influx rate remained elevated, being ~7-fold higher than the Na+ influx rate. These findings suggest that the loss of viability observed when glochidia were exposed to a high NaCl concentration (1.0g/L) could be caused by ionoregulatory disturbances mainly associated with an elevated Cl− influx.