Posts Tagged 'mollusks'

Ocean acidification alters the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and gene expression of a bivalve species, Sinonovacula constricta

Although the impacts of ocean acidification on fertilization, embryonic development, calcification, immune response, and behaviour have been well studied in a variety of marine organisms, the physiological and molecular mechanism manifesting acidification stress on behavioural response remains poorly understood. Therefore, the impacts of future ocean acidification scenarios (pH at 7.8, 7.6, and 7.4) on the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and expression of energy-producing-related genes of the razor clam Sinonovacula constricta were investigated in the present study. The results showed that elevated CO2 partial pressure ( pCO2) (pH at 7.6 and 7.4) led to a significant reduction in the digging depth of the razor clam. In addition, exposure to pCO2-acidified seawater depressed the metabolism and activity of Ca2+/Mg2+-ATPase, which may partially contribute to the reduced digging depth detected. Furthermore, the expression of energy-producing-related genes was generally induced by exposure to acidified seawater and could be accounted for by an increased energy demand under acidification stress. The results obtained suggest ocean acidification may exert a behavioural impact through altering physiological condition in the razor clam.

Continue reading ‘Ocean acidification alters the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and gene expression of a bivalve species, Sinonovacula constricta’

Genome-wide identification, characterization and expression analyses of TLRs in Yesso scallop (Patinopecten yessoensis) provide insight into the disparity of responses to acidifying exposure in bivalves

  Highlights

  • Eighteen TLR superfamily members were identified in the P. yessoensis genome.
  • Phylogenetic analysis confirmed duplication and expansion of TLR genes in mollusk.
  • The 18 PyTLRs showed different immune response patterns to acidifying exposure.
  • Adaptive recruitment of tandem duplication of TLR genes have been arisen to the immune stress.

Abstract

Toll-like receptors (TLRs) play a crucial role in innate immunity by recognizing specific pathogen-associated molecular patterns, including lipoproteins, lipopeptides, lipopolysaccharide, flagellin, dsRNA, ssRNA and CpG DNA motifs. Although significant effects of TLRs on immunity have been reported in most vertebrates and some invertebrates, the complete TLR superfamily has not been systematically characterized in scallops. In this study, 18 TLR genes were identified from Yesso scallop (Patinopecten yessoensis) using whole-genome scanning. Phylogenetic and protein structural analyses were performed to determine the identities and evolutionary relationships of the 18 genes. Extensive expansion of TLR genes from the Yesso scallop genome indicated gene duplication events. In addition, expression profiling of PyTLRs was performed at different acidifying exposure levels (pH = 6.50, 7.50) with different challenge durations (3, 6, 12 and 24 h) via in silico analysis using transcriptome and genome databases. Our results confirmed the inducible expression patterns of PyTLRs under acidifying exposure, and the responses to immune stress may have arisen through adaptive recruitment of tandem duplications of TLR genes. Collectively, this study provides novel insight into PyTLRs as well as the specific role and response of TLR signaling pathways in host immune responses against acidifying exposure in bivalves.

 

Continue reading ‘Genome-wide identification, characterization and expression analyses of TLRs in Yesso scallop (Patinopecten yessoensis) provide insight into the disparity of responses to acidifying exposure in bivalves’

Exposure history determines pteropod vulnerability to ocean acidification along the US West Coast

The pteropod Limacina helicina frequently experiences seasonal exposure to corrosive conditions (Ωar  < 1) along the US West Coast and is recognized as one of the species most susceptible to ocean acidification (OA). Yet, little is known about their capacity to acclimatize to such conditions. We collected pteropods in the California Current Ecosystem (CCE) that differed in the severity of exposure to Ωar conditions in the natural environment. Combining field observations, high-CO2 perturbation experiment results, and retrospective ocean transport simulations, we investigated biological responses based on histories of magnitude and duration of exposure to Ωar < 1. Our results suggest that both exposure magnitude and duration affect pteropod responses in the natural environment. However, observed declines in calcification performance and survival probability under high CO2 experimental conditions do not show acclimatization capacity or physiological tolerance related to history of exposure to corrosive conditions. Pteropods from the coastal CCE appear to be at or near the limit of their physiological capacity, and consequently, are already at extinction risk under projected acceleration of OA over the next 30 years. Our results demonstrate that Ωar exposure history largely determines pteropod response to experimental conditions and is essential to the interpretation of biological observations and experimental results.

Continue reading ‘Exposure history determines pteropod vulnerability to ocean acidification along the US West Coast’

Trade-offs in a high CO2 habitat on a subsea volcano: condition and reproductive features of a bathymodioline mussel

Northwest Eifuku submarine volcano (Mariana Volcanic Arc) emits very high concentrations of CO2 at a vent where the mussel Bathymodiolus septemdierum experiences pH as low as 5.2. We examined how this natural setting of high pCO2 influences shell, body, and reproductive condition. Calcification is highly compromised: at a given shell volume, shells from NW Eifuku weigh about half those from reference sites in the south Pacific, and dissolution of the inner shell is evident. However, the condition indices of some NW Eifuku mussels were equal to or higher than those from Lau back-arc basin and the New Hebrides Island Arc. NW Eifuku mussels in pH 5.2 fluids had the highest symbiont abundances in gill bacteriocytes, probably due to greater dissolved sulphide access. Excess energy demands imposed by high pCO2 conditions appears moderated by adequate food availability through symbiont chemosynthesis. In the sample with the lowest body condition, gametogenesis was lagging, although all mussels in high pCO2 had developing gonads and the complete gametogenic cycle was present in our samples. Gamete development is synchronous between sexes and is possibly periodic. While mussels are functionally dioecious, protogynous hermaphroditism can occur—a first record for the genus—which may be an adaptation to resource availability. B. septemdierum likely makes energy allocation trade-offs among calcification, body mass maintenance, reproduction and other processes to maximize fitness. We suggest that flexibility to divert energy from shell formation, combined with good food supply, can mitigate the manifestation of high CO2 stress on B. septemdierum.

Continue reading ‘Trade-offs in a high CO2 habitat on a subsea volcano: condition and reproductive features of a bathymodioline mussel’

Physiological responses to ocean acidification and warming synergistically reduce condition of the common cockle Cerastoderma edule

The combined effect of ocean acidification and warming on the common cockle Cerastoderma edule was investigated in a fully crossed laboratory experiment. Survival of the examined adult organisms remained high and was not affected by elevated temperature (+3 °C) or lowered pH (-0.3 units). However, the morphometric condition index of the cockles incubated under high pCO2 conditions (i.e. combined warming and acidification) was significantly reduced after six weeks of incubation. Respiration rates increased significantly under low pH, with highest rates measured under combined warm and low pH conditions. Calcification decreased significantly under low pH while clearance rates increased significantly under warm conditions and were generally lower in low pH treatments. The observed physiological responses suggest that the reduced food intake under hypercapnia is insufficient to support the higher energy requirements to compensate for the higher costs for basal maintenance and growth in future high pCO2waters.

Continue reading ‘Physiological responses to ocean acidification and warming synergistically reduce condition of the common cockle Cerastoderma edule’

Pteropod shell condition, locomotion, and long-term population trends in the context of ocean acidification and environmental change

Thecosome pteropods are planktonic mollusks that form aragonite shells and that may experience increased dissolution and other adverse effects due to ocean acidification. This thesis focuses on assessing the possible biological effects of ocean acidification on the shells and locomotion of pteropods and examining the response of a local pteropod population to environmental change over time. I analyzed shell condition after exposing pteropods to elevated CO2 as well as in natural populations to investigate the sensitivity of the shells of different species to aragonite saturation state (ΩA). The pteropods (Limacina retroversa) from laboratory experiments showed the clearest pattern of shell dissolution in response to decreased ΩA, while wild populations either had non-significant regional trends in shell condition (Clio pyramidata) or variability in shell condition that did not match expectations due to regional variability in ΩA (Limacina helicina). At locations with intermediate ΩA (1.5-2.5) the variability seen in L. helicina shell condition might be affected by food availability more than ΩA. I examined sinking and swimming behaviors in the laboratory in order to investigate a possible fitness effect of ocean acidification on pteropods. The sinking rates of L. retroversa from elevated CO2 treatments were slower in conjunction with worsened shell condition. These changes could increase their vulnerability to predators in the wild. Swimming ability was mostly unchanged by elevated CO2 after experiments that were up to three weeks in duration. I used a long-term dataset of pteropods in the Gulf of Maine to directly test whether there has been a population effect of environmental change over the past several decades. I did not observe a population decline between 1977 and 2015, and L. retroversa abundance in the fall actually increased over the time series. Analysis of the habitat use of L. retroversa revealed seasonal associations with temperature, salinity, and bottom depths. The combination of laboratory experiments and field surveys helped to address gaps in knowledge about pteropod ecology and improve our understanding of the effects of ocean acidification on pteropods.

Continue reading ‘Pteropod shell condition, locomotion, and long-term population trends in the context of ocean acidification and environmental change’

The impacts of seawater acidification on Ruditapes philippinarum sensitivity to carbon nanoparticles

In the present study, the impacts of multi-walled carbon nanotubes (MWCNTs), one of the most important NMs used in broad industrial and biomedical applications, on the clam Ruditapes philippinarum were evaluated under actual and predicted ocean acidification conditions. For this, oxidative stress, metabolic capacity and neurotoxicity related biomarkers were measured after a long-term exposure of clams to different conditions. The results obtained revealed that under low pH conditions the toxicity of MWCNTs was similar to the impacts measured under control pH. In both cases the energy-related responses in contaminated clams were altered with an increase of their metabolism which resulted into the expenditure of their energy reserves (lower glycogen content). Moreover, R. philippinarum showed oxidative stress when exposed to MWCNTs expressed by higher lipid peroxidation, lower ratio between reduced and oxidized glutathione and activation of antioxidant defences and biotransformation mechanisms. Additionally, neurotoxicity was observed by inhibition of Cholinesterases activity in organisms exposed to MWCNTs at both pHs.

Continue reading ‘The impacts of seawater acidification on Ruditapes philippinarum sensitivity to carbon nanoparticles’


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