Proteomic analysis during larval development and metamorphosis of the spionid polychaete Pseudopolydora vexillosa

<p>Abstract</p> <p>Background</p> <p>While the larval-juvenile transition (metamorphosis) in the spionid polychaete <it>Pseudopolydora vexillosa </it>involves gradual morphological changes and does not require substantial development of juvenile organs, the opposite occurs in the barnacle <it>Balanus amphitrite</it>. We hypothesized that the proteome changes during metamorphosis in the spionids are less drastic than that in the barnacles. To test this, proteomes of pre-competent larvae, competent larvae (ready to metamorphose), and juveniles of <it>P. vexillosa </it>were compared using 2-dimensional gel electrophoresis (2-DE), and they were then compared to those of the barnacle.</p> <p>Results</p> <p>Unlike the significant changes found during barnacle metamorphosis, proteomes of competent <it>P. vexillosa </it>larvae were more similar to those of their juveniles. Pre-competent larvae had significantly fewer protein spots (384 spots), while both competent larvae and juveniles expressed about 660 protein spots each. Proteins up-regulated during competence identified by MALDI-TOF/TOF analysis included a molecular chaperon (calreticulin), a signal transduction regulator (tyrosin activation protein), and a tissue-remodeling enzyme (metallopeptidase).</p> <p>Conclusions</p> <p>This was the first time to study the protein expression patterns during the metamorphosis of a marine polychaete and to compare the proteomes of marine invertebrates that have different levels of morphological changes during metamorphosis. The findings provide promising initial steps towards the development of a proteome database for marine invertebrate metamorphosis, thus deciphering the possible mechanisms underlying larval metamorphosis in non-model marine organisms.</p

Crystallographic Interdigitation in Oyster Shell Folia Enhances Material Strength

Shells of oyster species belonging to the genus Crassostrea have similar shell microstructural features comprising well-ordered calcite folia. However, the mechanical strengths of folia differ dramatically between closely related species. For example, the calcareous shells of the Hong Kong oyster Crassostrea hongkongensis are stronger than those of its closest relative, the Portuguese oyster, Crassostrea angulata. Specifically, after removal of organic content, the folia of C. hongkongensis are 200% tougher and able to withstand a 100% higher crushing force than that of C. angulata. Detailed analyses of shell structural and mechanical features support the hypothesis that crystallographic interdigitations confer elevated mechanical strength in C. hongkongensis oyster shells compared to C. angulata shells. Consequently, the folia of C. hongkongensis are structurally equipped to withstand a higher external load compared to C. angulata. The observed relationships between oyster shell structure, crystallography, and mechanical properties provided an insightful context in which to consider the likely fate of these two species in future climate change scenarios. Furthermore, the interdisciplinary approach developed in this study through integrating electron backscatter diffraction (EBSD) data into finite element analysis (FEA) could be applied to other biomineral systems to investigate the relationship between crystallography and mechanical behavior

Surviving the Anthropocene: the resilience of marine animals to climate change

If marine organisms are to persist through the Anthropocene, they will need to be resilient, but what is resilience, and can resilience of marine organisms build within a single lifetime or over generations? The aim of this review is to evaluate the resilience capacity of marine animals in a time of unprecedented global climate change. Resilience is the capacity of an ecosystem, society, or organism to recover from stress. Marine organisms can build resilience to climate change through phenotypic plasticity or adaptation. Phenotypic plasticity involves phenotypic changes in physiology, morphology, or behaviour which improve the response of an organism in a new environment without altering their genotype. Adaptation is an evolutionary longer process, occurring over many generations and involves the selection of tolerant genotypes which shift the average phenotype within a population towards the fitness peak. Research on resilience of marine organisms has concentrated on responses to specific species and single climate change stressors. It is unknown whether phenotypic plasticity and adaptation of marine organisms including molluscs, echinoderms, polychaetes, crustaceans, corals, and fish will be rapid enough for the pace of climate change

Ocean acidification reduces mechanical properties of the Portuguese oyster shell with impaired microstructure: a hierarchical analysis

Abstract. The rapidly intensifying process of ocean acidification (OA) in coastal areas due to anthropogenic CO2 is not only depleting carbonate ions necessary for calcification but also causing acidosis and disrupting internal pH homeostasis in several marine organisms. These negative consequences of OA on marine communities, particularly to shellfish oyster species, has been very well documented in recent studies, however, the consequences of these reduced or impaired calcification processes on the end-product, shells or skeletons, still remains one of the major research gaps. Shells produced by marine organisms under OA are expected to be corroded with disorganized or impaired crystal orientation or microstructures with reduced mechanical property. To bridge this knowledge gap and to test the above hypothesis, we investigated the effect of OA on shell of the commercially important oyster species (Crassostrea angulata) at ecologically and climatically relevant OA levels (using pH 8.1, 7.8, 7.5, 7.2 as proxies). In decreased pH conditions, a drop of shell hardness and stiffness was revealed by nanoindentation tests, while an evident loosened internal microstructure was detected by scanning electron microscopy (SEM). In contrary, the crystallographic orientation of oyster shell showed no significant difference with decreasing pH by Electron Back Scattered Diffraction (EBSD) analyses. These results indicate the loosened internal microstructure may be the cause of the OA induced reduction in shell hardness and stiffness. Micro-computed tomography analysis (Micro-CT) indicated that an overall "down-shifting" of mineral density in the shell with decreasing pH, which implied the loosened internal microstructure may run through the shell, thus inevitably limiting the effectiveness of the shell defensive function. This study surfaces potential bottom-up deterioration induced by OA on oyster shells, especially in their early juvenile life stage. This knowledge is critical to forecast the survival and production of edible oysters in future ocean. </jats:p

Temperature Modulates Coccolithophorid Sensitivity of Growth, Photosynthesis and Calcification to Increasing Seawater pCO2

Increasing atmospheric CO2 concentrations are expected to impact pelagic ecosystem functioning in the near future by driving ocean warming and acidification. While numerous studies have investigated impacts of rising temperature and seawater acidification on planktonic organisms separately, little is presently known on their combined effects. To test for possible synergistic effects we exposed two coccolithophore species, Emiliania huxleyi and Gephyrocapsa oceanica, to a CO2 gradient ranging from ,0.5–250 mmol kg21 (i.e. ,20–6000 matm pCO2) at three different temperatures (i.e. 10, 15, 20uC for E. huxleyi and 15, 20, 25uC for G. oceanica). Both species showed CO2-dependent optimum-curve responses for growth, photosynthesis and calcification rates at all temperatures. Increased temperature generally enhanced growth and production rates and modified sensitivities of metabolic processes to increasing CO2. CO2 optimum concentrations for growth, calcification, and organic carbon fixation rates were only marginally influenced from low to intermediate temperatures. However, there was a clear optimum shift towards higher CO2 concentrations from intermediate to high temperatures in both species. Our results demonstrate that the CO2 concentration where optimum growth, calcification and carbon fixation rates occur is modulated by temperature. Thus, the response of a coccolithophore strain to ocean acidification at a given temperature can be negative, neutral or positive depending on that strain’s temperature optimum. This emphasizes that the cellular responses of coccolithophores to ocean acidification can only be judged accurately when interpreted in the proper eco-physiological context of a given strain or species. Addressing the synergistic effects of changing carbonate chemistry and temperature is an essential step when assessing the success of coccolithophores in the future ocean

Seawater carbonate chemistry and larval growth response of the Portuguese oyster (Crassostrea angulata) in a laboratory experiment

Rising anthropogenic carbon dioxide (CO2) dissolving into coastal waters is decreasing the pH and carbonate ion concentration, thereby lowering the saturation state of calcium carbonate (CaCO3) minerals through a process named ocean acidification (OA). The unprecedented threats posed by such low pH on calcifying larvae of several edible oyster species have not yet been fully explored. Effects of low pH (7.9, 7.6, 7.4) on the early growth phase of Portuguese oyster (Crassostrea angulata) veliger larvae was examined at ambient salinity (34 ppt) and the low-salinity (27 ppt) treatment. Additionally, the combined effect of pH (8.1, 7.6), salinity (24 and 34 ppt) and temperature (24 °C and 30 °C) was examined using factorial experimental design. Surprisingly, the early growth phase from hatching to 5-day-old veliger stage showed high tolerance to pH 7.9 and pH 7.6 at both 34 ppt and 27 ppt. Larval shell area was significantly smaller at pH 7.4 only in low-salinity. In the 3-factor experiment, shell area was affected by salinity and the interaction between salinity and temperature but not by other combinations. Larvae produced the largest shell at the elevated temperature in low-salinity, regardless of pH. Thus the growth of the Portuguese oyster larvae appears to be robust to near-future pH level (> 7.6) when combined with projected elevated temperature and low-salinity in the coastal aquaculture zones of South China Sea

Seawater carbonate chemistry and survival and growth of oyster species Crassostrea hongkongensis

The majority of common edible oysters are projected to grow more slowly and have smaller impaired shells because of anthropogenic CO2-induced reductions in seawater carbonate ion concentration and pH, a process called ocean acidification (OA). Recent evidence has shown that OA has carryover effects, for example, larvae exposed to OA will also exhibit either positive or negative effects after metamorphosis. This study examined the hidden carryover effects of OA exposure during parental and larval stages on post-metamorphic traits of the commercially important oyster species Crassostrea hongkongensis. Adults of C. hongkongensis were exposed to control pH (pHNBS 8.0) and OA-induced low pH (pHNBS 7.4) conditions. Their larval offspring were then exposed to the same aquarium conditions before being out-planted as post-metamorphic juveniles at a mariculture site for 10 months. Initially, larval offspring were resilient to low pH with or without parental exposure. The larvae exposed to low pH had significantly faster development and higher percentage of settlement success compared to control groups. The out-planted juveniles with parental exposure had improved survival and growth compared to juveniles without parental exposure, regardless of the larval exposure history. This implies that transgenerational effects due to parental exposure not only persists but also have a greater influence than the within-generational effects of larval exposure. Our results shed light on the importance of linking the various life history stages when assessing the OA-induced carryover capacity of C. hongkongensis in the natural environment. Understanding these linked relationships helps us better predict the species rapid adaptation responses in the face of changing coastal conditions due to OA

Seawater carbonate chemistry and wild oyster population resistance to ocean acidification

The carbon dioxide induced ocean acidification (OA) process is well known to have profound effects on physiology, survival and immune responses in marine organisms, and particularly calcifiers including edible oysters. At the same time, some wild populations could develop a complex and sophisticated immune system to cope with multiple biotic and abiotic stresses, such as bacterial infections and OA, over the long period of coevolution with the environment. However, it is unclear how immunological responses and the underlying mechanisms are altered under the combined effect of OA and bacterial infection, especially in the ecologically and economically important edible oysters. Here, we collected the wild population of oyster species Crassostrea hongkongensis (the Hong Kong oyster) from their native estuarine area and carried out a bacterial challenge with the worldwide pervasive pathogen of human foodborne disease, Vibrio parahaemolyticus, to investigate the host immune responses and molecular mechanisms under the high-CO2 and low pH-driven OA conditions. The wild population had a high immune resistance to OA, but the resistance is compromised under the combined effect of OA and bacterial infection both in vivo or in vitro. We classified all transcriptomic genes based on expression profiles and functional pathways and identified the specifically switched on and off genes and pathways under combined effect. These genes and pathways were mainly involved in multiple immunological processes including pathogen recognition, immune signal transduction and effectors. This work would help understand how the immunological function and mechanism response to bacterial infection in wild populations and predict the dynamic distribution of human health-related pathogens to reduce the risk of foodborne disease under the future climate change scenario