The effect of interspecific and intraspecific diversity on microplastic ingestion in two co-occurring mussel species in South Africa

Interspecific and intraspecific diversity are essential components of biodiversity with far-reaching implications for ecosystem function and service provision. Importantly, genotypic and phenotypic variation within a species can affect responses to anthropogenic pressures more than interspecific diversity. We investigated the effects of interspecific and intraspecific diversity on microplastic ingestion by two coexisting mussel species in South Africa, Mytilus galloprovincialis and Perna perna, the latter occurring as two genetic lineages. We found significantly higher microplastic abundance in M. galloprovincialis (0.54 ± 0.56 MP items g-1WW) than P. perna (0.16 ± 0.21 MP items g-1WW), but no difference between P. perna lineages. Microbeads were the predominant microplastic (76 % in P. perna, 99 % in M. galloprovincialis) and polyethylene the prevalent polymer. Interspecific differences in microplastic abundance varied across locations, suggesting diverse sources of contamination. We suggest that microplastic ingestion can be species-specific even in organisms that coexist and play similar functional roles within ecosystems.

Accumulation and ecotoxicological risk of weathered polyethylene (wPE) microplastics on green mussel (Perna viridis)

Recent studies have shown that organisms including humans are exposed to microplastics directly or indirectly. The present study aims to examine the ingestion of these microplastics and the consequences of the same by studying the accumulation behavior of weathered Polyethylene (wPE) microplastics. The Perna viridis were exposed chronically to three different environmentally relevant concentrations of wPE for 30 days, followed by a one-week depuration phase. There was no mortality observed in the control and exposed groups, but the feeding rate was observed to have substantially decreased in the group exposed to higher concentration (3 μgL^-1) of wPE. It was also observed that a higher number of wPE particles accumulated in the intestine of exposed organisms. Interestingly, the present study revealed the presence of the substantial number of wPE particles in exposed organisms, which may adversely affect the internal organs as well as growth and reproduction. This study perceived that accumulation is marginally influenced by size of wPE. Similarly, biomarker analysis showed that wPE exposure significantly altered both the metabolism and histology of the internal organs of the exposed organisms. Overall, the study confirmed that the intestine was the most sensitive organ followed by gills, adductor muscles, and foot tissue adding new insights into the adverse effects of wPE in the marine ecosystem.

Biochemical metal accumulation effects and metalloprotein metal detoxification in environmentally exposed tropical Perna perna mussels

Marine bivalves have been widely applied as environmental contamination bioindicators, although studies concerning tropical species are less available compared to temperate climate species. Assessments regarding Perna perna mytilid mussels, in particular, are scarce, even though this is an extremely important species in economic terms in tropical countries, such as Brazil. To this end, Perna perna mytilids were sampled from two tropical bays in Southeastern Brazil, one anthropogenically impacted and one previously considered a reference site for metal contamination. Gill metallothionein (MT), reduced glutathione (GSH), carboxylesterase (CarbE) and lipid peroxidation (LPO) were determined by UV-vis spectrophotometry, and metal and metalloid contents were determined by inductively coupled plasma mass spectrometry (ICP-MS). Metalloprotein metal detoxification routes in heat-stable cellular gill fractions were assessed by size exclusion high performance chromatography (SEC-HPLC) coupled to an ICP-MS. Several associations between metals and oxidative stress endpoints were observed at all four sampling sites through a Principal Component Analysis. As, Cd, Ni and Se contents, in particular, seem to directly affect CarbE activity. MT is implicated in playing a dual role in both metal detoxification and radical oxygen species scavenging. Differential SEC-HPLC-ICP-MS metal-binding profiles, and, thus, detoxification mechanisms, were observed, with probable As-, Cu- and Ni-GSH complexation and binding to low molecular weight proteins. Perna perna mussels were proven adequate tropical bioindicators, and further monitoring efforts are recommended, due to lack of data regarding biochemical metal effects in tropical species. Integrated assessments, as performed herein demonstrate, are invaluable in evaluating contaminated aquatic environments, resulting in more accurate ecological risk assessments.

Effects of DCOIT (4,5-dichloro-2-octyl-4-isothiazolin-3-one) to the haemocytes of mussels Perna perna

Bivalve molluscs rely only on an innate immune system to execute cellular and humoral processes. Haemocytes, the haemolymph circulating cells, play a major role in this type of immunity, principally regarding cellular defences. Considering that environmental pollutants can affect the immune system of invertebrates, this work evaluated the effects of the antifouling biocide 4,5-dicloro-2-n-octil-4-isotiazolin-3-ona (DCOIT) on the haemocytes of mussels Perna perna. Individuals were exposed to 0 (control), 0.1 μg L^-1 and 10 μg L^-1 of DCOIT for up to 96 h. The analysed parameters included: total (THC) and differential (DHC) haemocyte count, cellular viability, adhesion capacity, phagocytic activity, levels of reactive oxygen species and DNA damage. Moreover, the stress on stress (SOS) response of mussels was analysed as a general stress index. The results show that DCOIT increased the haemocyte adhesion capacity and caused a decrease in THC and in the haemocyte viability after 24 h of exposure. After 96 h of exposure, DCOIT only affected the haemocyte adhesion capacity, which was decreased by biocide exposure. Moreover, exposure to DCOIT for 96 h did not affect the capacity for air survival of mussels. These results indicate that DCOIT interferes in important parameters associated with the innate immunity of P. perna, mainly after 24 h of exposure. It is suggested that the animals were able to develop some compensatory response strategy, making them more resistant to the biocide.

Effects of chlorothalonil on the antioxidant defense system of mussels Perna perna

Chlorothalonil is an effective fungicide used in agriculture and formulations of antifouling paints, which use and possible toxicity has been generating great concern. Thus, the present study investigated the effects of chlorothalonil on the antioxidant defense system (ADS) of the mussel Perna perna. The ADS was evaluated in gills and digestive gland after 24 h and 96 h of exposure to environmental relevant levels of chlorothalonil (0.1 and 10 μg/L). The activity of the enzymes superoxide dismutase (SOD), catalase (CAT), glutamate cysteine-ligase (GCL) and glutathione S-transferase (GST), levels of non-enzymatic defenses, represented by glutathione (GSH), and lipoperoxidation (LPO) and protein carbonyls (PCO) were evaluated. Results indicated that exposure to chlorothalonil is affecting the ADS in both tissues. While the activity of SOD increased and GST and GSH were not altered in gills, they decreased in digestive gland after 24 h of exposure to 10 μg/L of chlorothalonil. The contrasting results indicate that gills and digestive gland presented different patterns of responses after exposure to chlorothalonil. Moreover, a tissue-specific response to chlorothalonil was observed. Gills could be acting as the first line of defense, presenting higher enzymatic levels with minor effects on the parameters analyzed. On the other hand, digestive gland, with lower levels of antioxidant defenses, was the most affect organ by chlorothalonil. It also should be highlighted that the fungicide reduced the glutathione metabolism in the digestive gland, which can lead to an imbalance of the redox state within the cells of animals.

Proteomic profile in the mussel Perna viridis after short-term exposure to the brown tide alga Aureococcus anophagefferens

Blooms of Aureococcus anophagefferens, referred to as brown tides are responsible for massive mortalities and recruitment failure of some bivalves. However, the molecular mechanisms underlying the toxicity remain elusive despite its biological significance, and the information currently available on the molecular effects is still insufficient. In this study, to evaluate the toxicity and associated mechanism of A. anophagefferens on bivalves, we analyzed the protein expression profiles in digestive glands of the A. anophagefferens-exposed Perna viridis by using iTRAQ. A total of 3138 proteins were identified in the digestive glands of A. anophagefferens-exposed P. viridis based on iTRAQ. Amongst, a repertoire of 236 proteins involved in cell, cell part, catalytic activity, metabolic process, biological regulation, immune system process, and response to stimulus were found to be differentially expressed. Functional analysis of the differentially expressed proteins demonstrated that innate immune system of P. viridis was activated, and some proteins associated with stress response and lipid metabolism were induced after exposure to A. anophagefferens. Additionally, MDA content, SOD activity and GSH-Px activity was increased significantly in the digestive gland of A. anophagefferens-exposed P. viridis. Taken together, our results indicated that the A. anophagefferens could induce oxidative stress, activate complement system and alter fat acid metabolism of P. viridis.

Ecotoxicological effects of losartan on the brown mussel Perna perna and its occurrence in seawater from Santos Bay (Brazil)

The antihypertensive losartan (LOS) has been detected in wastewater and environmental matrices, however further studies focused on assessing the ecotoxicological effects on aquatic ecosystems are necessary. Considering the intensive use of this pharmaceutical and its discharges into coastal zones, our study aimed to determine the environmental concentrations of LOS in seawater, as well as to assess the biological effects of LOS on the marine bivalve Perna perna. For this purpose, fertilization rate and embryolarval development were evaluated through standardized assays. Phase I (ethoxyresorufin O‑deethylase EROD and dibenzylfluorescein dealkylase DBF) and II (glutathione S-transferase GST) enzymes, glutathione peroxidase (GPx), Cholinesterase (ChE), lipoperoxidation (LPO) and DNA damage were used to analyze sublethal responses in gills and digestive gland of adult individuals. Lysosomal membrane stability was also assessed in hemocytes. Our results showed the occurrence of LOS in 100% of the analyzed water samples located in Santos Bay, Sao Paulo, Brazil, in a range of 0.2 ng/L-8.7 ng/L. Effects on reproductive endpoints were observed after short-term exposure to concentrations up to 75 mg/L. Biomarker responses demonstrated the induction of CYP450 like activity and GST in mussel gills exposed to 300 and 3000 ng/L of LOS, respectively. GPx activity was also increased in concentration of exposure to 3000 ng/L of LOS. Cyto-genotoxic effects were found in gills and hemocytes exposed in concentrations up to 300 ng/L. These results highlighted the concern of introducing this class of contaminants into marine environments, and pointed out the need to include antihypertensive compounds in environmental monitoring programs.

Interannual variability in Dinophysis spp. abundance and toxin accumulation in farmed mussels (Perna perna) in a subtropical estuary

This study evaluated an 8-year dataset (2007 to 2015, except 2008) in the attempt to identify the most susceptible periods for the occurrence of diarrheic shellfish poisoning (DSP) episodes associated with the presence of toxigenic dinoflagellates, Dinophysis spp., in the mussel farming area of Babitonga Bay (southern Brazil). Dinophysis acuminata complex was the most frequent (present in 66% of the samples) and abundant (max. 4100 cells L^-1) taxon, followed by D. caudata (14%; max. 640 cells L^-1) and D. tripos (0.9%; max. 50 cells L^-1). There was a marked onset of the annual rise in Dinophysis spp. abundance during weeks 21-25 (early winter) of each year, followed by a second peak on week 35 (spring). Mussel (Perna perna) samples usually started testing positive in DSP mouse bioassays (MBA) in late winter. Positive results were more frequent in 2007 and 2011 when the mean D. acuminata complex abundance was ~ 500 cells L^-1. Although positive DSP-MBA results were observed in only 11% of the samples during the studied period, the toxin okadaic acid (OA) was present in 90% of the analyzed mussels (max. 264 μg kg^-1). MBA results were positive when D. acuminata complex cell densities exceed 1200 ± 300 cells L^-1, while trace toxin amounts could be detected at cell densities as low as 150 ± 50 cells L^-1 (free OA) to 200 ± 100 cells L^-1 (conjugated OA). Low salinity and the meteorological conditions triggered by La Niña events were the main factors associated with both Dinophysis abundance and OA accumulation in mussels.

Continuous Exposure to Microplastics Does Not Cause Physiological Effects in the Cultivated Mussel Perna perna

The environmental impact of microplastics is a challenging theme, especially under realistic experimental conditions. We investigated physiological responses to 0.1-1.0 μm PVC particles intake by the mussel Perna perna after a relative long-term exposure (90 days) at a less extreme concentration compared with previous studies (0.125 g/L). Microplastic intake was inferred by the presence of PVC in the feces of mussels, and physiological damages were assessed through ingestion rate, assimilation efficiency, growth rate, cellular and molecular biomarkers (lysosomal integrity, lipid peroxidation, and DNA damage), and condition index. All physiological responses showed nonsignificant effects of the microplastics on the exposed mussels. We suggest that, despite the experimental concentration of microplastics, mussels were able to acclimate to the exposure through their abilities for long-term recovery and tolerance to stresses. These data have positive implications for environmental health and in terms of human food resource because mussel farming is a worldwide practice that heavily relies on plastic materials, increasing the chances of microplastic exposure and mussels contamination.

Exposure to crack cocaine causes adverse effects on marine mussels Perna perna

Our study aimed to evaluate crack cocaine effects in different life stages of the marine mussel Perna perna. For this purpose, fertilization rate, embryo-larval development, lysosomal membrane stability and DNA strand breaks were assessed. Effect concentrations in gametes and in larval development were found after 1h (IC₅₀=23.53mg·L^-1) and 48h (IC₅₀=16.31mg·L^-1), respectively. The highest tested concentration showing no acute toxicity (NOEC) was 10mg·L^-1, while the lowest observed effect concentration (LOEC) was 20mg·L^-1. NOEC concerning embryo-larval development was 0.625mg·L^-1, while the LOEC was 1.25mg·L^-1. Cyto-genotoxic effects were evidenced in mussels exposed to crack cocaine concentrations ranging from 5 to 500μg·L^-1. Our results report the first data on effects of an illicit drug to marine organisms and should encourage further ecotoxicological studies of these contaminants of emerging concern in coastal ecosystems.

Hypoxia effects on oxidative stress and immunocompetence biomarkers in the mussel Perna perna (Mytilidae, Bivalvia)

This study investigated the effects of hypoxia on oxidative stress response and immune function in mussels Perna perna exposed to air for 6, 12, 24 and 48 h. In air-exposed mussels, the antioxidant enzymes superoxide dismutase (SOD), catalase, and glutathione reductase (GR) activities were lower in gill tissues (24-48 h) and digestive gland (12 h), while the glutathione peroxidase and GR activities were increased in the digestive gland (48 h). In both tissues, aerial exposure promoted a rapid (6 h) and persistent (up to 48 h) increase of glutathione levels. Decreased hemocyte count and viability, as well as increased phagocytic activity and cellular adhesion capacity were detected after prolonged aerial exposure (>12 h). In summary, induction of thiol pools, altered antioxidant enzyme activities, and activation of immune responses were detected in hypoxia exposed brown mussels, indicating hypoxia induced tissue-specific responses in both antioxidant and immune systems.

Tolerance to stress differs between Asian green mussels Perna viridis from the impacted Jakarta Bay and from natural habitats along the coast of West Java

It is an open question whether adverse habitat conditions, characteristic for many anthropogenically impacted coastal habitats, can determine resistance to abiotic stress in populations of residing invertebrates. We tested experimentally for differences in stress tolerance between individuals of the Asian green mussel Perna viridis stemming from the heavily impacted Jakarta Bay and from two natural sites, Lada Bay and Pelabuhan Ratu, West Java. Mussel performance under hyposalinity and hypoxia was assessed in laboratory assays by measuring fitness-related response variables, e.g. body condition index, relative shell weight, byssus production, respiration rates and survival. We found stress-specific and population-specific differences in mussel resistance to adverse conditions: Individuals from the impacted Jakarta Bay performed better under hypoxia than their conspecifics from the natural sites, whereas the latter were more resistant to hyposalinity. We explain these differences by differential acclimation to environmental conditions in the respective habitats and by diverging degrees of food supply.

Comparison of condition index in the green-lipped mussel Perna viridis between Sebatu and Pasir Panjang, Peninsular Malaysia

The condition index (which relates to the tissue dry weight to shell volume) of the green-lipped mussel Perna viridis was investigated at Sebatu in Melaka and Pasir Panjang in Negri Sembilan from September 2003 to February 2004. Monthly samples of P. viridis were collected from culturing rafts at both sites. Variations in the average monthly condition index (CI) of P. viridis ranged from 21.06 to 26.72 g cm(-3) and 15.18 to 19.41 g cm(-3) in Sebatu and Pasir Panjang, respectively. Salinity values were lowest in November between 27.93 to 28.10 ppt in Sebatu and Pasir Panjang, respectively. Salinity then started increasing gradually until it reached 33.26 ppt in Sebatu and 31.23 ppt in Pasir Panjang in the month of February. Chlorophylla in Pasir Panjang showed higher fluctuation, ranging from 2.93 to 14.39 mg/L, while in Sebatu the fluctuations were lower and ranged between 7.70 and 9.37 mg l(-1). Rapid decline in CI values were recorded during January in Sebatu and February in Pasir Panjang. However, this rapid declining state of CI in P. viridis was an indication of its spawning period, when their gametes were released in the water column. These findings would help in the development of captive breeding techniques and mass seed production in aquaculture.

Cheating the Locals: Invasive Mussels Steal and Benefit from the Cooling Effect of Indigenous Mussels

The indigenous South African mussel Perna perna gapes during periods of aerial exposure to maintain aerobic respiration. This behaviour has no effect on the body temperatures of isolated individuals, but when surrounded by conspecifics, beneficial cooling effects of gaping emerge. It is uncertain, however, whether the presence of the invasive mussel Mytilus galloprovincialis limits the ability of P. perna for collective thermoregulation. We investigated whether varying densities of P. perna and M. galloprovincialis influences the thermal properties of both natural and artificial mussel beds during periods of emersion. Using infrared thermography, body temperatures of P. perna within mixed artificial beds were shown to increase faster and reach higher temperatures than individuals in conspecific beds, indicating that the presence of M. galloprovincialis limits the group cooling effects of gaping. In contrast, body temperatures of M. galloprovincialis within mixed artificial mussel beds increased slower and exhibited lower temperatures than for individuals in beds comprised entirely of M. galloprovincialis. Interestingly, differences in bed temperatures and heating rates were largely dependent on the size of mussels, with beds comprised of larger individuals experiencing less thermal stress irrespective of species composition. The small-scale patterns of thermal stress detected within manipulated beds were not observed within naturally occurring mixed mussel beds. We propose that small-scale differences in topography, size-structure, mussel bed size and the presence of organisms encrusting the mussel shells mask the effects of gaping behaviour within natural mussel beds. Nevertheless, the results from our manipulative experiment indicate that the invasive species M. galloprovincialis steals thermal properties as well as resources from the indigenous mussel P. perna. This may have significant implications for predicting how the co-existence of these two species may change as global temperatures continue to rise.

Field Measurements Indicate Unexpected, Serious Underestimation of Mussel Heart Rates and Thermal Tolerance by Laboratory Studies

Attempts to predict the response of species to long-term environmental change are generally based on extrapolations from laboratory experiments that inevitably simplify the complex interacting effects that occur in the field. We recorded heart rates of two genetic lineages of the brown mussel Perna perna over a full tidal cycle in-situ at two different sites in order to evaluate the cardiac responses of the two genetic lineages present on the South African coast to temperature and the immersion/emersion cycle. "Robomussel" temperature loggers were used to monitor thermal conditions at the two sites over one year. Comparison with live animals showed that robomussels provided a good estimate of mussel body temperatures. A significant difference in estimated body temperatures was observed between the sites and the results showed that, under natural conditions, temperatures regularly approach or exceed the thermal limits of P. perna identified in the laboratory. The two P. perna lineages showed similar tidal and diel patterns of heart rate, with higher cardiac activity during daytime immersion and minimal values during daytime emersion. Comparison of the heart rates measured in the field with data previously measured in the laboratory indicates that laboratory results seriously underestimate heart rate activity, by as much as 75%, especially during immersion. Unexpectedly, field estimates of body temperatures indicated an ability to tolerate temperatures considered lethal on the basis of laboratory measurements. This suggests that the interaction of abiotic conditions in the field does not necessarily raise vulnerability to high temperatures.

Uptake, release, and absorption of nutrients into the marine environment by the green mussel (Perna viridis)

The nutrient uptake and release by the mussels in relation with amount of food consumption are emphasised in this research. Results of the study demonstrate that about 16% of the total mass dry weight food consumed by the mussels was released as faeces. The depositions of particulate carbon, nitrogen, and phosphorus in mussel faeces were found to be 26.3, 5.7, and 0.6mg/day/indv respectively. Soluble inorganic nutrients such as NH4(+)-N (2.5mg/day/indv), and PO4(3-)-P (0.6mg/day/indv) were also released as mussel excretion. The nutrient absorption efficiency for the green mussel body was found to be 65.1% for carbon, 62.1% for nitrogen, and 79.2% for phosphorus. Subsequently, green mussels can remove particulate carbon, nitrogen and phosphorus at 108.1, 13.5, and 4.6mg/day/indv from aquatic systems. Finally, the results can help in estimating the carrying capacity of mussel cultivation without deteriorating the water quality in marine ecosystems.

Cryopreservation of Greenshell™ mussel (Perna canaliculus) sperm

Cryopreservation is a valuable technique for aquaculture as it enables a library or bank of genetically valuable animals to be maintained in a cost-effective manner. Here, we describe a method to cryopreserve the sperm of the Greenshell™ mussel (Perna canaliculus) and how to use the sperm post-thawing to maximize larval production from thawed sperm in selective breeding.

Can additives ameliorate oxidative stress and improve development of Greenshell mussel (Perna canaliculus) oocytes during cryopreservation?

BACKGROUND

Cryopreservation of P. canaliculus oocytes has not yet been achieved.

OBJECTIVE

The present study is to investigate whether the incorporation of: DMSO (0.09%), α-tocopherol (0.1 mM) plus taurine (1 mM) and ethylenediaminetetraacetic acid (EDTA; 0.1 mM), is beneficial during cryopreservation.

METHODS

These three additives were incorporated to both the cryoprotectant (CPA) and recovery media, and evaluated in terms of development and oxidative stress at three key stages of cryopreservation: 1) cryoprotectant addition [10% v/v ethylene glycol plus 0.2M trehalose; final concentration], 2) cooling to -6 degrees C, and 3) cooling to -35 degrees C and liquid nitrogen immersion.

RESULTS

Over all treatments (including controls) progressive cryopreservation steps resulted in a decrease in fertilization and development to D-larvae, an increase in macromolecular oxidative damage markers (protein carbonyls, lipid hydroperoxides and oxidized DNA), and a decrease in enzymatic (superoxide dismutase, catalase, glutathione S-transferase and glutathione reductase) and non-enzymatic antioxidants.

CONCLUSION

Whilst results varied, the major effects of the additives were the improved percentage fertilization and a decrease in macromolecular damage.

Detachment, displacement and reattachment activity in a freshwater byssate mussel (Limnoperna fortunei): the effects of light, temperature and substratum orientation

The ability of the freshwater bivalve Limnoperna fortunei to voluntarily detach from the substratum, crawl and reattach as a function of illumination, temperature, substratum orientation, and mussel size was investigated. Thirty-two per cent of the 879 experimental animals detached and reattached elsewhere at least once during five- to eight-day experiments. The proportions of mobile mussels were significantly higher in permanent darkness than under permanent illumination. Displacement distances were also higher in darkness, but statistical differences with illuminated individuals were inconclusive. No evidence of circadian rhythms was detected. Mobile mussels were often significantly smaller than non-mobile individuals. It was not possible to detect the effect of water temperature (22°C and 31°C), or substratum orientation (topside and underside) on mussel mobility, but because the power of the statistical tests was low, future experiments are needed to confirm this result. The ability of mussels to voluntarily detach and reattach elsewhere has important implications for biofouling control.

Proteomic profile in Perna viridis after exposed to Prorocentrum lima, a dinoflagellate producing DSP toxins

In the current study, we compared protein profiles in gills of Perna viridis after exposure to Prorocentrumlima, a dinoflagellate producing DSP toxins, and identified the differential abundances of protein spots using 2D-electrophoresis. After exposure to P. lima, the level of okadaic acid (a main component of DSP toxins) in gills of P. viridis significantly increased at 6 h, but mussels were all apparently healthy without death. Among the 28 identified protein spots by MALDI TOF/TOF-MS, 12 proteins were up-regulated and 16 were down-regulated in the P. lima-exposed mussels. These identified proteins were involved in various biological activities, such as metabolism, cytoskeleton, signal transduction, response to oxidative stress and detoxification. Taken together, our results indicated that the presence of P. lima caused DSP toxins accumulation in mussel gill, and might consequently induce cytoskeletonal disorganization,oxidative stress, a dysfunction in metabolism and ubiquitination/proteasome activity.

Establishing the thermal threshold of the tropical mussel Perna viridis in the face of global warming

With increasing recognition that maximum oxygen demand is the unifying limit in tolerance, the first line of thermal sensitivity is, as a corollary, due to capacity limitations at a high level of organisational complexity before individual, molecular or membrane functions become disturbed. In this study the tropical mussel Perna viridis were subjected to temperature change of 0.4 °C per hour from ambient to 8-36 °C. By comparing thermal mortality against biochemical indices (hsp70, gluthathione), physiological indices (glycogen, FRAP, NRRT) and behavioural indices (clearance rate), a hierarchy of thermal tolerance was therein elucidated, ranging from systemic to cellular to molecular levels. Generally, while biochemical indices indicated a stress signal much earlier than the more integrated behavioural indices, failure of the latter (indicating a tolerance limit and transition to pejus state) occurred much earlier than the other indices tending towards thermal extremities at both ends of the thermal spectrum.

Genotoxicity of perfluorinated chemicals (PFCs) to the green mussel (Perna viridis)

Concerns regarding perfluorinated chemicals (PFCs) have grown significantly in recent years. However, regulations and guidelines regarding the emission and treatment of PFCs are still missing in most parts of the world, mostly due to the lack of PFC toxicity data. In the current study, the genotoxic effects of four common PFCs, named perfluorooctanesulfonate (PFOS), perfluoroocanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) were investigated on marine mussels. The effects of exposure time and concentration on the toxic behavior of the compounds were also examined. Genotoxicity of PFCs was assessed in biomarker assays, showing that exposure to the target compounds could damage the organism's genetic material to varying extents, including DNA strand breaks and fragmentation, chromosomal breaks and apoptosis. The adverse effects increased with both exposure concentration and time and were related with the organism burden of PFCs. The integrated biomarker response analysis demonstrated that PFOS exhibited a higher genotoxicity than the other tested compounds. The EC50 values and confidence intervals based on integrative genotoxicity were 33 (29-37), 594 (341-1036), 195 (144-265) and 78 (73-84) μg/L for PFOS, PFOA, PFNA and PFDA respectively, classifying PFOS as a highly genotoxic compound. Although primary DNA damage was shown to be recoverable after exposure ceased, permanent genetic damage caused by elevated PFC concentrations was not restored. This is the first ecotoxicity study of PFCs that focuses on the genotoxic effects of the compounds, clearly indicating the genotoxicity of the tested PFCs and demonstrating that functional groups have a major impact on the compounds' genotoxic behavior.

Ecological relevance of Sentinels' biomarker responses: a multi-level approach

In response to the need for more sensitive and rapid indicators of environmental quality, sublethal effects on the lowest levels of biological organization have been investigated. The ecological relevance of these responses assumes a prevailing role to assure effectiveness as indicator of ecological status. This study aimed to investigate the linkages between biomarker responses of caged bivalves and descriptive parameters of macrobenthic community structure. For this purpose a multi-level environmental assessment of marine and estuarine zones was performed in São Paulo coast, Brazil. Multivariate analysis was applied to identify linkages between biological responses and ecological indices, as well as to characterizing the studied stations. Individuals of the marine mussel Perna perna caged along Santos Bay showed signs of oxidative stress, lysosomal membrane destabilization, histological alterations and reduced embryonic development. The estuarine oyster Crassostrea rhizophorae caged along Santos Port Channel showed alterations on biotransformation enzymes and antioxidant system, DNA damage and lysosomal membrane destabilization. The benthic community analysis showed reduced richness and diversity in the same areas of the Santos bay and estuary where biomarker responses were altered. Our results revealed that xenobiotics are inducing physiological stress, which may lead to changes of the benthic community structure and deterioration of the ecological status over time. Integrating biomarker responses and ecological indexes improved certainty that alterations found at community level could be related to xenobiotic as stressors, which was very useful to improve the discriminatory power of the environmental assessment.

Screening for antioxidant and detoxification responses in Perna canaliculus Gmelin exposed to an antifouling bioactive intended for use in aquaculture

Polygodial is a drimane sesquiterpene dialdehyde derived from certain terrestrial plant species that potently inhibits ascidian metamorphosis, and thus has potential for controlling fouling ascidians in bivalve aquaculture. The current study examined the effects of polygodial on a range of biochemical biomarkers of oxidative stress and detoxification effort in the gills of adult Perna canaliculus Gmelin. Despite high statistical power and the success of positive controls, the antioxidant enzymes glutathione reductase (GR), glutathione peroxidase (GPOX), catalase (CAT), and superoxide dismutase (SOD); thiol status, as measured by total glutathione (GSH-t), glutathione disulphide (GSSG), and GSH-t/GSSG ratio; end products of oxidative damage, lipid hydroperoxides (LHPO) and protein carbonyls; and detoxification pathways, represented by GSH-t and glutathione S-transferase (GST), were unaffected in the gills of adult P. canaliculus exposed to polygodial at 0.1 or 1 × the 99% effective dose in fouling ascidians (IC₉₉). Similarly, GR levels, thiol status, and detoxification activities were unaffected in mussels exposed to polygodial at 10 × the IC₉₉, although GPOX, CAT, and SOD activities increased. However, the increases were small relative to positive controls, no corresponding oxidative damage was detected, and this concentration greatly exceeds effective doses required to inhibit fouling ascidians in aquaculture. These findings compliment a previous study that established the insensitivity to polygodial of P. canaliculus growth, condition, and mitochondrial functioning, providing additional support for the suitability of polygodial for use as an antifouling agent in bivalve aquaculture.

Habitat degradation correlates with tolerance to climate-change related stressors in the green mussel Perna viridis from West Java, Indonesia

It is unclear whether habitat degradation correlates with tolerance of marine invertebrates to abiotic stress. We therefore tested whether resistance to climate change-related stressors differs between populations of the green mussel Perna viridis from a heavily impacted and a mostly pristine site in West Java, Indonesia. In laboratory experiments, we compared their oxygen consumption and mortality under lowered salinity (-13 and -18 units, both responses), hypoxia (0.5 mg/l, mortality only) and thermal stress (+7 °C, mortality only). Mussels from the eutrophied and polluted Jakarta Bay showed a significantly smaller deviation from their normal oxygen consumption and higher survival rates when stressed than their conspecifics from the unaffected Lada Bay. This shows that human induced habitat degradation correlates with mussel tolerance to environmental stress. We discuss possible mechanisms - e.g. the selection of tolerant genotypes or habitat-specific differences in the nutritional status of the mussels - that could explain our observation.

[Metallothioneins in Perna viridis (Bivalvia: Mytilidae): seasonal variation and its relation to reproductive biology]

Metallothionein is a cytosolic protein found in a variety of tissues and have been involved in the regulation of essential trace metals such as copper and zinc, and in the detoxification of essential and nonessential metals. With the aim to study their seasonal variation and their possible role in reproductive behavior, we evaluated metallothioneins (Mts) in Perna viridis, taken from Rio Caribe and Chacopata localities in the North coast of Sucre state, Venezuela. A total of 325 samples were obtained from February to December 2003. We determined the following biometric indices in bivalves: Condition Index (CI), meat yield (RC) and dry weight-length relationship (PSL). Besides, Mts in whole tissue were separated by molecular exclusion chromatography, Sephadex G-50 and quantified by saturation with cadmium. Our results showed that the biometric indices (RC and PSL) had seasonal variations between localities and maturity stages, with the exception of IC. No significant differences were found between sexes. Mts showed seasonal variations between localities, with the highest concentrations between February and March, and minimum ones between September and December, coinciding with the respectively high and low productivity periods in the area. The mussels from Rio Caribe had higher Mts concentration than those from Chacopata. Furthermore, immature mussels showed the highest Mts concentration while the lowest was found in spawned specimens. We found a significant negative relationship between Mts and CI. Our results demonstrated that MTs in Perna viridis are influenced by the condition index and reproductive status, as well as physico-chemical factors in the marine environment.

Energetics of byssus attachment and feeding in the green-lipped mussel Perna canaliculus

In most animals, significant increases in metabolic rate are due to activity and to feeding (known as apparent specific dynamic action). We determined the energetic costs of activity and feeding in adult green-lipped mussels (Perna canaliculus). Maximal metabolic rate was determined, using closed-chamber respirometry, during byssus re-attachment, during specific dynamic action after 16 h of feeding with Isochrysis galbana, and for the two activities combined, in 23 mussels. Metabolic rate was significantly elevated above rest by about 1.9-fold during byssus attachment (17.1 ± 1.53 μg O(2) h(-1) g(-1) whole mussel wet weight at rest, increased to 27.9 ± 0.91 μg O(2) h(-1) g(-1)), and by 2.2-fold after feeding (31.4 ± 1.20 μg O(2) h(-1) g(-1)). Combined feeding and byssus attachment led to a still higher metabolic rate (34.0 ± 1.23 μg O(2) h(-1) g(-1)). Behavior was also significantly altered, with mussels being almost continuously open during attachment and after feeding (90%-99% of the time); however, the time spent open during the day decreased, reaching a minimum of 52% ± 9% 3 days after feeding, and remained low (67%-82%) for the following 45-day starvation period. Significant diurnal differences were observed, with mussels continuously (92%-100%) open at night. The key findings from this study are that green-lipped mussels (1) have an aerobic scope of approximately 2-fold; (2) reach a higher metabolic rate during feeding than during activity, and the two combined can raise the metabolic rate higher still; (3) display a marked diurnal behavior.

Influence of size and density on filtration rate modeling and nutrient uptake by green mussel (Perna viridis)

This study investigates green mussel filtration rates based on variation of the mussel size and density, and attempts to correlate these with the amount of Chaetoceros calcitrans consumed by kinetic modeling. The filtration rates were found to be more effective in small mussels and with greater volumes of seawater/mussel which represent low mussel densities in the mussel farms. Under field condition, the first order kinetic model is useful for evaluation of mussel filtration rate. However, the composite exponential kinetic model was determined to better describe filtration rates in a close system. Higher ratios of seawater volume L/g DW mussel tissue, resulted in an increasing filtration rate until a maximum plateau was reached at 10.37 L/h/g DW tissue as determined by first order kinetics. Based on the filtration rate, carbon, nitrogen, and phosphorus uptake by green mussels were found to be 2128.72, 265.41, and 66.67 mg/year/indv, respectively.

Impairment of green-lipped mussel (Perna canaliculus) physiology by waterborne cadmium: relationship to tissue bioaccumulation and effect of exposure duration

Laboratory studies were performed to assess the impact of acute and subchronic cadmium (Cd) exposure on the green-lipped mussel, Perna canaliculus. A 96 h median lethal concentration (LC(50)) value of 8160 μg L(-1) was determined, characterising this species as relatively tolerant to Cd exposure. Acute (96 h; at 2000 and 4000 μg Cd L(-1)) and subchronic (28 d; at 200 and 2000 μg Cd L(-1)) waterborne exposures were then conducted to investigate the impact of Cd exposure on physiological responses (e.g. clearance (feeding) rate, absorption efficiency, oxygen uptake, ammonia production, oxygen to nitrogen ratio, scope for growth) and tissue Cd accumulation. Cd accumulation in digestive gland showed saturation with respect to increasing exposure concentration, while the gill tissue Cd accumulation followed a positive linear relationship with Cd exposure level. Clearance rates declined during both acute and subchronic exposures at levels of 2000 μg Cd L(-1) or higher. Impairments of clearance rates were strongly correlated with tissue Cd accumulation. Coupled with their importance as a food source, and their wide coastal distribution, these data suggests that P. canaliculus may be a species useful as an indicator species for trace metal pollution in coastal environments.

Induction of settlement in mussel (Perna canaliculus) larvae by vessel noise

Underwater sound plays an important role in the settlement behaviour of many coastal organisms. Large steel-hulled vessels are known to be a major source of underwater sound in the marine environment. The possibility that underwater sound from vessels may promote biofouling of hulls through triggering natural larval settlement cues was investigated for the mussel, Perna canaliculus. The mussel larvae showed significantly faster settlement when exposed to the underwater noise produced by a 125-m long steel-hulled passenger and freight ferry. Median time to attachment on the substrata (ie settlement) was reduced by 22% and the time taken for all experimental larvae to settle was reduced by 40% relative to a silent control. There was no difference in the survival of the mussel larvae among the various noise treatments. The decrease in settlement time of the mussel larvae appeared to correlate with the intensity of the vessel sound, suggesting that underwater sound emanating from vessels may be an important factor in exacerbating hull fouling by mussels.

Immune responses to combined effect of hypoxia and high temperature in the green-lipped mussel Perna viridis

Flow cytometry was used to examine immune responses in haemocytes of the green-lipped mussel Perna viridis under six combinations of oxygen level (1.5 mg O2 l(-1), 6.0 mg O2 l(-1)) and temperature (20 °C, 25 °C and 30 °C) at 24 h, 48 h, 96 h and 168 h. The mussels were then transferred to normoxic condition (6.0 mg O2 l(-1)) at 20 °C for further 24 h to study their recovery from the combined hypoxic and temperature stress. Esterase (Est), reactive oxygen species (ROS), lysosome content (Lyso) and phagocytosis (Pha) were reduced at high temperatures, whereas hypoxia resulted in higher haemocyte mortality (HM) and reduced phagocytosis. For HM and Pha, changes were observed after being exposed to the stresses for 96 h, whereas only a 24 h period was required for ROS and Lyso, and a 48 h one for Est. Recovery from the stresses was observed for HM and Pha but not other immune responses.

The combined effects of oxygen availability and salinity on physiological responses and scope for growth in the green-lipped mussel Perna viridis

Mussels were maintained for 4 weeks under different combinations of dissolved oxygen concentration (1.5, 3.0 and 6.0 mg O2 l(-1)) and salinity (15, 20, 25 and 30) in a 3×4 factorial design experiment. Clearance rate (CR), absorption efficiency (AE), respiration rate (RR) and scope for growth (SFG) decreased with decreasing salinity and dissolved oxygen concentration (DO), while excretion rate (ER) increased with decreasing salinity and increasing DO. The O:N ratio was <10 at salinities of 15 and 20, irrespective of DO levels. SFG was negative in most of the treatments, except for those under 6.0 mg O2 l(-1) or at a salinity of 30 when DO was lower. The results may help explain the distribution pattern of Perna viridis in Hong Kong waters and provide guidelines for mussel culture site selection.

Physiological energetics of the brown mussel Perna perna (L.) transplanted in the Itajaí-Açu river mouth, Southern Brazil

Groups of the mussel Perna perna were transplanted to two points and at three different depths in the coastal region close to the Itajaí-Açu River mouth, an impacted river in the south of Brazil. With the objective of evaluating the physiology changes in the organisms in relation to the control area (origin of the organisms), the clearance, respiration and excretion rates, absorption efficiency and growth were estimated. The levels of metals in the organism tissue were determined in an attempt to explain the physiological changes occurring in the study area. Organisms from Point 2 placed near the bottom showed physiological changes in comparison to the control and the transplanted organisms from Point 1. Point 2 showed greater sediment resuspension and availability of trace metals to the organisms closer to the bed. The increase in Cr concentration in the tissues of the organisms (up to 0.21 mg kg(-1) ww) was not sufficient to explain the decrease in the inhibition of clearance (28.8%) and in the absorption efficiency (15.7%), or the increased excretion rate (282.5%), which led to the organisms having a reduced scope for growth (48.6%). This indicates the possible presence of other contaminants, which were not measured, and which probably had synergistic action with the trace metals investigated.

Effect of sea cucumber (Australostichopus mollis) grazing on coastal sediments impacted by mussel farm deposition

Deposit-feeding holothurians are important processors of surface sediments in many coastal marine systems. The present study examined the effect of grazing by the sea cucumber Australostichopus mollis on sediment impacted by green-lipped mussel biodeposits (faeces and pseudofaeces) from coastal aquaculture activities. Grazing effects were investigated in a series of tank-based feeding experiments conducted over 1, 2, 4 and 8 week periods. Sediment quality indicators routinely applied to determine the impacts of coastal aquaculture were used to evaluate sediment health from grazed and ungrazed sediments. Sea cucumber grazing resulted in reductions in total organic carbon, chlorophyll a and phaeopigment, as well as chlorophyll a/phaeopigment ratio of impacted sediments. These results demonstrate that sea cucumber grazing significantly reduces the accumulation of both organic carbon and phytopigments associated with biodeposition from mussel farms. Sea cucumber grazing offers a means of constraining or reversing the pollutive impacts of coastal bivalve aquaculture.

Sublethal effect of silver and chromium in the green mussel Perna viridis with reference to alterations in oxygen uptake, filtration rate and membrane bound ATPase system as biomarkers

Perna viridis is an ideal animal for studying the impairment caused by the effects of heavy metals that are often detected in coastal areas. Preliminary bioassay tests revealed that the lethal (LC(100)), median lethal (LC(50)) and sublethal (LC(0)) concentration of silver and chromium to P. viridis were 6.5, 4.0, 2.0 mg l(-1) and 4.5, 2.5, 1.0 mg l(-1), respectively. Toxic effect of silver and chromium was evaluated in the green mussel P. viridis, with reference to oxygen consumption, filtration rate and ATPase system in laboratory experiments. These parameters were selected as the end point of sublethal stress. Oxygen consumption and filtration rates were calculated as a measure of decline in the dissolved oxygen level and algal concentration (feed) in the aquaria water, respectively. Silver and chromium affects both oxygen consumption and filtration rate significantly (P<0.01) at 96 h when compared to control. The activity of ATPases system in the gills, hepatopancreas, ovary and muscle of mussels were inhibited by silver and chromium indicating that metals exerted significant toxic effect. The inhibition of Na(+)K(+) ATPase, Ca(2+) ATPase and Mg(2+) ATPase in the mussels were significant (P<0.05) for silver and highly significant (P<0.01) for chromium, which indicates that chromium was more toxic to mussels when compared to silver. The assessment of oxygen consumption, filtration and ATPases system can thus be used as a valid biomarker in aquatic ecotoxicology studies.

Trace metals in mussel shells and corresponding soft tissue samples: a validation experiment for the use of Perna perna shells in pollution monitoring

The uptake of Cr, Mn, Ni, Cu, Zn, Cd and Pb in soft tissue of Perna perna mussels and their shells has been studied in aquarium experiments in which mussels were exposed for 30 or 60 days to seawater spiked with different concentrations of these contaminants (125 and 500 microg L(-1)). Tissue samples were analyzed after acid digestion by conventional solution nebulization ICP-MS. Laser ablation ICP-MS was used for the quantitative determination of trace elements in different areas of the corresponding shells. With the exception of Mn and Zn, all other elements studied showed a significant concentration enhancements in soft tissue, with the magnitude of this enhancement following the order: Cr > Ni > Cd > Cu > Pb. A corresponding increase in most contaminants, although less pronounced, was also observed in the newly formed growth rings of mussel shells, contributing to the validation of Perna perna mussel shell as a bioindicator of toxic elements.

Seasonal Variations of Lipid Content and Composition in Perna viridis

The total lipid content, composition of main lipid classes, composition of sterols and composition of fatty acids in the main glycerolipids of Perna viridis were analyzed through four seasons using TLC-FID and GLC. Mussel samples were collected during different seasons between 2003 and 2004 from Shengsi Island, Zhejiang Province, China and stored frozen prior to freeze-drying and lipid extraction. Ten grams of dried mussel powder of each season were analyzed. Total lipid content ranged from 14.5 g/100 g in spring month to 7.8 g/100 g dried mussel powder in autumn month. The predominant lipid in spring month was triacylglycerol (TAG), however, in the other three seasons the phospholipids (PL) was the main lipid class. The most abundant fatty acid in TAG, PL and phosphatidylcholine (PC) was 16:0, with the summer samples having the highest proportion (24-30% of total fatty acid) and winter the lowest (14-22%). In phosphatidylethanolamine (PE), the spring samples had the highest proportions of 16:0. The predominant polyunsaturated fatty acids (PUFA) were 22:6n-3 and 20:5n-3 in TAG, PL, PE and PC (25-40%). The proportions of 22:6n-3 and 20:5n-3 were higher in spring than in other seasons in PL and PE. There were nine sterols identified, with cholesterol being the predominant sterol, and other main ones were desmostersol/brassicasterol and 24-methylenecholesterol. Proportions of other fatty acids in different lipid fractions and the sterol compositions as well also varied seasonally. There were subject to the seasonal variations. Differences in lipid content and composition, fatty acid composition in different lipid fractions may be caused by multiple factors such as lifecycle, sex, variation of plankton in different seasons and temperature, which could influence physiological activities and metabolism.

Oxidative stress in Perna perna and other bivalves as indicators of environmental stress in the Brazilian marine environment: Antioxidants, lipid peroxidation and DNA damage

Oxidative stress can take place in marine bivalves under a series of environmental adverse conditions. The study of different systems related to oxidative stress in these organisms can give important information about their physiological status and also about environmental health. Bivalves have been proposed as good sentinel organisms in pollution monitoring studies through the analysis of biochemical biomarkers, and most of the biomarkers analyzed are those related to oxidative stress. However, it is very important to know how other environmental factors not associated to the presence of pollutants might affect these parameters. We have studied a series of mechanisms related to oxidative stress in mussels which inhabit the Brazilian coast, especially in Perna perna species, subjected to different stress conditions, such as the exposure to different contaminants in the laboratory and in the field, the exposure of mussels to air and re-submersion, simulating the tidal oscillations, and in mussels collected at different seasons. Both oxidative damage levels and antioxidant defense systems were strongly affected by the different environmental stress. This review summarizes the data obtained in some studies carried out in bivalves from the Brazilian coast.

Temporal genetic differentiation in cultured and natural beds of the brown mussel Perna perna (Mytilidae)

Perna perna is the most important cultivated mussel of Santa Catarina, Brazil, sustaining an important economic input for many local families. Natural stocks of P. perna are depleted by the extraction of adults and seeds for consumption and culture. The aim of the present study was to use the microsatellite locus pms-2 to study the variation of the genetic composition and diversity between natural and cultured stocks in samples of 2001 and 2005 from Penha, Santa Catarina. DNA was extracted from adductor muscle by Chelex/proteinase-K and phenol/chloroform protocols. Amplification by polymerase chain reaction was performed using specific primers for analyzing the pms-2 locus. Polymerase chain reaction products were submitted to vertical denatured 6% polyacrylamide gel electrophoresis and horizontal 2% agarose gel electrophoresis, and visualized by silver staining and ethidium bromide, respectively. Allele diversity and heterozygote deficiency were higher for samples of 2005 than for those of 2001. No significant genetic differentiation was found between natural and cultured stocks of 2001 by the chi(2) test, but G(2) (likelihood ratio) detected slight differences (I = 0.949; chi(2), P = 0.147; G(2), P = 0.046), while cultured and natural stocks of 2005 were very different (I = 0.798, P = 0.006). Between the years of 2001 and 2005, a large change in genetic composition was observed (I = 0.582; P < 0.001). Although nothing is known about natural changes in the genetic composition of this species with time, the results suggest a strong impact of human activities on natural stocks of P. perna, which is expected to be related to heavy extraction and farming.

Physiological rates in different classes of sizes of Perna perna (Linnaeus, 1758) submmited to experimental loboratory conditions

Physiological studies of the mussel Perna perna in Brazil are almost 30 years behind those of other, more exhaustively investigated species, such as Mytilus edulis. Little is known about the variations in physiological rates due to size and the consequences of maintaining P. perna in laboratory conditions. This work investigated the variations in respiration, clearance, excretion and absorption efficiency rates of P. perna, classified by size and acclimatized in a laboratory, monitoring the mussels’ respiration rates and biometry over a period of 30 days, in laboratory conditions. The respiration, clearance and excretion rates presented an allometric relation with the dry weight of the organisms, with b values of 0.66, 0.48 and 0.91 respectively. On the other hand, these same rates, when considered by weight (specific rates) showed a relationship that was inverse to the size of the organisms. Only the absorption efficiency was independent of the weight of the mussel. In terms of acclimatization, it was observed that it takes 10 days for the respiration rate of the mussel P. perna to stabilize in laboratory conditions, after which it follows a routine metabolism.

Pollution monitoring in Southeast Asia using biomarkers in the mytilid mussel Perna viridis (Mytilidae: Bivalvia)

Mytilid mussels have been extensively used in marine pollution monitoring programmes in temperate regions of the world although widespread subtropical representatives such as Perna viridis have only comparatively recently been utilised to monitor the sublethal effects of pollution in Southeast Asia. P. viridis is considered a subtropical equivalent of the temperate Mytilus sp. and has considerable potential for pollution monitoring throughout its geographical range. This paper reviews the current status of biomarkers in P. viridis and provides some recommendations on biological-effects monitoring to facilitate the assessment of coastal pollution in Southeast Asia.