Simulated Marine Heat Wave Alters Abundance and Structure of Vibrio Populations Associated with the Pacific Oyster Resulting in a Mass Mortality Event

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. Marine heat waves are predicted to become more frequent and intense due to anthropogenically induced climate change, which will impact global production of seafood. Links between rising seawater temperature and disease have been documented for many aquaculture species, including the Pacific oyster Crassostrea gigas. The oyster harbours a diverse microbial community that may act as a source of opportunistic pathogens during temperature stress. We rapidly raised the seawater temperature from 20 °C to 25 °C resulting in an oyster mortality rate of 77.4%. Under the same temperature conditions and with the addition of antibiotics, the mortality rate was only 4.3%, strongly indicating a role for bacteria in temperature-induced mortality. 16S rRNA amplicon sequencing revealed a change in the oyster microbiome when the temperature was increased to 25 °C, with a notable increase in the proportion of Vibrio sequences. This pattern was confirmed by qPCR, which revealed heat stress increased the abundance of Vibrio harveyi and Vibrio fortis by 324-fold and 10-fold, respectively. Our findings indicate that heat stress-induced mortality of C. gigas coincides with an increase in the abundance of putative bacterial pathogens in the oyster microbiome and highlights the negative consequences of marine heat waves on food production from aquaculture

Disease prevention strategies for QX disease (Marteilia sydneyi) of Sydney rock oysters (Saccostrea glomerata)

The Sydney rock oyster (Saccostrea glomerata) forms the basis of an important aquaculture industry on the east coast of Australia. During the 1970s, production of S. glomerata began to decline, in part as a result of mortalities arising from Queensland unknown (QX) disease. Histological studies implicated the paramyxean parasite Marteilia sydneyi in the disease outbreaks. Disease zoning was implemented to prevent the spread of M. sydneyi-infected oysters. This control measure hindered rock oyster farming, which historically has relied on transferring wild-caught spat between estuaries for on-growing to market size and has not prevented the subsequent occurrence of QX disease in the Georges and Hawkesbury rivers in central New South Wales. Management of QX disease has been hampered by the complicated life cycle of M. sydneyi, with outbreaks of QX disease likely to be regulated by a combination of the abundance of intermediate host of M. sydneyi, environmental stressors, and the immunocompetence of S. glomerata. The future of the Sydney rock oyster industry relies on understanding these factors and progressing the industry from relying on farming wild-caught seed to the successful commercialization of hatchery-produced QX-resistant S. glomerata

Determination of glucose exchange rates and permeability of erythrocyte membrane in preeclampsia and subsequent oxidative stress-related protein damage using dynamic-19F-NMR

The cause of the pregnancy condition preeclampsia (PE) is thought to be endothelial dysfunction caused by oxidative stress. As abnormal glucose tolerance has also been associated with PE, we use a fluorinated-mimic of this metabolite to establish whether any oxidative damage to lipids and proteins in the erythrocyte membrane has increased cell membrane permeability. Data were acquired using 19F Dynamic-NMR (DNMR) to measure exchange of 3-fluoro-3-deoxyglucose (3-FDG) across the membrane of erythrocytes from 10 pregnant women (5 healthy control women, and 5 from women suffering from PE). Magnetisation transfer was measured using the 1D selective inversion and 2D EXSY pulse sequences, over a range of time delays. Integrated intensities from these experiments were used in matrix diagonalisation to estimate the values of the rate constants of exchange and membrane permeability. No significant differences were observed for the rate of exchange of 3-FDG and membrane permeability between healthy pregnant women and those suffering from PE, leading us to conclude that no oxidative damage had occurred at this carrier-protein site in the membrane

"Nested" cryptic diversity in a widespread marine ecosystem engineer: a challenge for detecting biological invasions

<p>Abstract</p> <p>Background</p> <p>Ecosystem engineers facilitate habitat formation and enhance biodiversity, but when they become invasive, they present a critical threat to native communities because they can drastically alter the receiving habitat. Management of such species thus needs to be a priority, but the poorly resolved taxonomy of many ecosystem engineers represents a major obstacle to correctly identifying them as being either native or introduced. We address this dilemma by studying the sea squirt <it>Pyura stolonifera</it>, an important ecosystem engineer that dominates coastal communities particularly in the southern hemisphere. Using DNA sequence data from four independently evolving loci, we aimed to determine levels of cryptic diversity, the invasive or native status of each regional population, and the most appropriate sampling design for identifying the geographic ranges of each evolutionary unit.</p> <p>Results</p> <p>Extensive sampling in Africa, Australasia and South America revealed the existence of "nested" levels of cryptic diversity, in which at least five distinct species can be further subdivided into smaller-scale genetic lineages. The ranges of several evolutionary units are limited by well-documented biogeographic disjunctions. Evidence for both cryptic native diversity and the existence of invasive populations allows us to considerably refine our view of the native versus introduced status of the evolutionary units within <it>Pyura stolonifera </it>in the different coastal communities they dominate.</p> <p>Conclusions</p> <p>This study illustrates the degree of taxonomic complexity that can exist within widespread species for which there is little taxonomic expertise, and it highlights the challenges involved in distinguishing between indigenous and introduced populations. The fact that multiple genetic lineages can be native to a single geographic region indicates that it is imperative to obtain samples from as many different habitat types and biotic zones as possible when attempting to identify the source region of a putative invader. "Nested" cryptic diversity, and the difficulties in correctly identifying invasive species that arise from it, represent a major challenge for managing biodiversity.</p

Genomic view of the evolution of the complement system

The recent accumulation of genomic information of many representative animals has made it possible to trace the evolution of the complement system based on the presence or absence of each complement gene in the analyzed genomes. Genome information from a few mammals, chicken, clawed frog, a few bony fish, sea squirt, fruit fly, nematoda and sea anemone indicate that bony fish and higher vertebrates share practically the same set of complement genes. This suggests that most of the gene duplications that played an essential role in establishing the mammalian complement system had occurred by the time of the teleost/mammalian divergence around 500 million years ago (MYA). Members of most complement gene families are also present in ascidians, although they do not show a one-to-one correspondence to their counterparts in higher vertebrates, indicating that the gene duplications of each gene family occurred independently in vertebrates and ascidians. The C3 and factor B genes, but probably not the other complement genes, are present in the genome of the cnidaria and some protostomes, indicating that the origin of the central part of the complement system was established more than 1,000 MYA

Bioaccumulation of heavy metals by tunicates

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Intraspecific differences in the transcriptional stress response of two populations of Sydney rock oyster increase with rising temperatures

The vulnerability of sessile organisms to warming temperatures may depend on their capacity to adaptively alter their expression of genes associated with stress mitigation. We compared the transcriptional profile of 2 populations of Sydney rock oysters Saccostrea glomerata (one that had been selectively bred over 7 generations for fast growth and disease resistance and one wild type that had not been subjected to selection) following exposure to an artificial temperature gradient in the field. Oysters were attached to white, grey or black stone pavers that experienced mean maximum substrate temperatures of approximately 34, 37 and 40°C, respectively, at low tide. Across all pavers, selectively bred oysters suffered 12% higher mortality than wild-type oysters, although this difference was not significant. Expression profiles did not differ between oyster populations on the coolest (white) pavers. However, divergent transcriptional profiles of genes associated with the key intracellular stress mechanisms of antioxidant defence, heat shock response, energy metabolism and the cytoskeleton were detected in oysters on the hottest (black) pavers. Expression of these genes was upregulated at high temperatures by the selectively bred oysters but displayed little change, or was suppressed at high temperature among the nonselected wild-type oysters. One potential explanation is that the selectively bred oysters have traded off rapid growth for a lower thermal maximum. Complementary physiological and ecological studies are needed to confirm this hypothesis.Dominic McAfee, Vivian R. Cumbo, Melanie J. Bishop, David A. Rafto

Aquatic animal health subprogram: Development of a DNA microarray to identify markers of disease in pearl oysters (Pinctada maxima) and to assess overall oyster health

This project used DNA-based technology to study the effects of environmental stress on pearl oysters. During the oyster farming process, oysters are subjected to a range of changes in their environment, such as fluctuating temperature and salinity. These changes are exacerbated by farming practices, during which oysters are exposed to additional stresses, such as routine antifouling and nucleation. All of these factors have the potential to stress oysters, potentially affecting their growth, susceptibility to disease and other important characteristics that decrease productivity. At its most basic level, stress causes changes in the activity of genes in oysters, switching some on and turning others off. It is these changes in gene activity that alter characteristics such as growth rate and susceptibility to disease

Aquatic animal health subprogram: Development of a DNA microarray to identify markers of disease in pearl oysters (Pinctada maxima) and to assess overall oyster health

This project used DNA-based technology to study the effects of environmental stress on pearl oysters. During the oyster farming process, oysters are subjected to a range of changes in their environment, such as fluctuating temperature and salinity. These changes are exacerbated by farming practices, during which oysters are exposed to additional stresses, such as routine antifouling and nucleation. All of these factors have the potential to stress oysters, potentially affecting their growth, susceptibility to disease and other important characteristics that decrease productivity. At its most basic level, stress causes changes in the activity of genes in oysters, switching some on and turning others off. It is these changes in gene activity that alter characteristics such as growth rate and susceptibility to disease