Aaron Wiegand

Spatial analysis of biomineralization associated gene expression from the mantle organ of the pearl oyster Pinctada maxima

BackgroundBiomineralization is a process encompassing all mineral containing tissues produced within an organism. One of the most dynamic examples of this process is the formation of the mollusk shell, comprising a variety of crystal phases and microstructures. The organic component incorporated within the shell is said to dictate this architecture. However general understanding of how this process is achieved remains ambiguous. The mantle is a conserved organ involved in shell formation throughout molluscs. Specifically the mantle is thought to be responsible for secreting the protein component of the shell. This study employs molecular approaches to determine the spatial expression of genes within the mantle tissue to further the elucidation of the shell biomineralization.ResultsA microarray platform was custom generated (PmaxArray 1.0) from the pearl oyster Pinctada maxima. PmaxArray 1.0 consists of 4992 expressed sequence tags (ESTs) originating from mantle tissue. This microarray was used to analyze the spatial expression of ESTs throughout the mantle organ. The mantle was dissected into five discrete regions and analyzed for differential gene expression with PmaxArray 1.0. Over 2000 ESTs were determined to be differentially expressed among the tissue sections, identifying five major expression regions. In situ hybridization validated and further localized the expression for a subset of these ESTs. Comparative sequence similarity analysis of these ESTs revealed a number of the transcripts were novel while others showed significant sequence similarities to previously characterized shell related genes.ConclusionsThis investigation has mapped the spatial distribution for over 2000 ESTs present on PmaxArray 1.0 with reference to specific locations of the mantle. Expression profile clusters have indicated at least five unique functioning zones in the mantle. Three of these zones are likely involved in shell related activities including formation of nacre, periostracum and calcitic prismatic microstructure. A number of novel and known transcripts have been identified from these clusters. The development of PmaxArray 1.0, and the spatial map of its ESTs expression in the mantle has begun characterizing the molecular mechanisms linking the organics and inorganics of the molluscan shell.

Transcriptome Analysis of the Sydney Rock Oyster, Saccostrea glomerata: Insights into Molluscan Immunity

Background Oysters have important ecological functions in their natural environment, acting as global carbon sinks and improving water quality by removing excess nutrients from the water column. During their life-time oysters are exposed to a variety of pathogens that can cause severe mortality in a range of oyster species. Environmental stressors encountered in their habitat can increase the susceptibility of oysters to these pathogens and in general have been shown to impact on oyster immunity, making immune parameters expressed in these marine animals an important research topic. Results Paired-end Illumina high throughput sequencing of six S. glomerata tissues exposed to different environmental stressors resulted in a total of 484,121,702 paired-end reads. When reads and assembled transcripts were compared to the C. gigas genome, an overall low level of similarity at the nucleotide level, but a relatively high similarity at the protein level was observed. Examination of the tissue expression pattern showed that some transcripts coding for cathepsins, heat shock proteins and antioxidant proteins were exclusively expressed in the haemolymph of S. glomerata, suggesting a role in innate immunity. Furthermore, analysis of the S. glomerata ORFs showed a wide range of genes potentially involved in innate immunity, from pattern recognition receptors, components of the Toll-like signalling and apoptosis pathways to a complex antioxidant defence mechanism. Conclusions This is the first large scale RNA-Seq study carried out in S. glomerata, showing the complex network of innate immune components that exist in this species. The results confirmed that many of the innate immune system components observed in mammals are also conserved in oysters; however, some, such as the TLR adaptors MAL, TRIF and TRAM are either missing or have been modified significantly. The components identified in this study could help explain the oysters’ natural resilience against pathogenic microorganisms encountered in their natural environment.

The contribution of energy systems during the upper body Wingate anaerobic test.

The purpose of this study was to measure the contribution of the aerobic, anaerobic lactic, and alactic systems during an upper body Wingate Anaerobic test (WAnT). Oxygen uptake and blood lactate were measured before, during, and after the WAnT and body composition analyzed by dual-energy X-ray absorptiometry. The contribution of the energy systems was 11.4% ± 1.4%, 60.3% ± 5.6%, and 28.3% ± 4.9% for the aerobic, anaerobic lactic, and alactic systems, respectively.

Use of local ecological knowledge in the management of algal blooms

More frequent and severe algal blooms are symptomatic of increasing ecosystem stress in coastal waters. Economic losses typically follow and local governments are forced to ‘manage’ this issue. Because many blooms are not monitored, local ecological knowledge (LEK) and oral history are the only practical tools to obtain data on bloom characteristics and identify their drivers. LEK was applied to outbreaks of brown algae on popular tourist beaches in south-east Queensland (Australia). Structured interviews with local citizens who had a close and frequent connection with the ocean provided 541 bloom records, which showed that blooms are regional (≥400 km) rather than local, and that they are a historical (≥40 years) rather than a recent phenomenon. LEK frequently cited that particular wind regimes coincided with the arrival of blooms, but this could not be verified by statistical cross-validation with empirical data. Harnessing LEK was valuable in engaging citizens, in generating testable hypotheses about plume causes, in providing a previously unrecognized historical perspective and in identifying the correct spatial scale of the issue. Multi-pronged approaches will be most effective in addressing blooms where local mitigation actions are combined with broader regional coastal environmental conservation efforts.

Changes in drive phase lower limb kinematics during a 60 min cycling time trial

OBJECTIVES The aim of this study was to evaluate changes in the three dimensional lower limb kinematics during a simulated cycling time trial. DESIGN Repeated measures. METHODS Ten experienced male road cyclists performed a 60 min cycling test at a workload based on previous onset of blood lactate accumulation (OBLA) testing. The time trial (TT) was divided into six 10 min periods consisting of 8 min cycling at steady state (88% of OBLA) followed by a 90 s effort phase (140% of OBLA) and a 30 s recovery phase (60% of OBLA). Three-dimensional kinematic data (200 Hz) were recorded in the last minute of each steady state phase with specific attention directed at changes in range of motion (ROM) and consistency of orientation at the hip, knee and ankle joints during drive phase. RESULTS from repeated measures ANOVA indicated a mean effect for test duration on the drive phase ROM in both hip extension (p=0.027) and ankle dorsi flexion (p<0.001). The SD of the mean tibial rotation during the drive phase was the only measure of movement consistency that showed an effect for test duration (p=0.031). CONCLUSIONS These findings indicated that participants tended to increase the ROM in hip extension and ankle flexion during drive phase at the end of a TT. Changes in the consistency of tibial rotation during the drive phase may be an important indicator of fatigue and should be monitored by coaches during training due to its possible relationship with injury and fatigue.

A systematic approach for modelling quantitative lake ecosystem data to facilitate proactive urban lake management

BackgroundThe management of the health of urban lake systems is often reactive and is instigated in response to poor aesthetic quality or physicochemical measurements, rather than from an overall assessment of ecosystem health. Interpreting physicochemical monitoring data in isolation is problematic for two main reasons: the suite of parameters that are monitored may be limited; and the contribution that any single parameter has towards water quality or health varies considerably depending on the nature of the system of interest. Extending monitoring programs to include flora and fauna results in a better dataset of ecosystem status, but also increases the complexity in interpreting whether the status is good or poor.ResultsThis paper details a process by which a large set of quantitative biological, physical, chemical and social indicators may be transformed into a simple, but informative, numerical index that represents the overall ecosystem health, while also identifying the likely source and scale of pressure for remedial management action. The flexibility of the proposed approach means that it can be readily adapted to other lake systems and environments, or even to include or exclude different indicators. A case study is presented in which the model is used to assess a comprehensive longitudinal dataset that resulted from monitoring a constructed urban lake in Southeast Queensland, Australia.ConclusionsThe sensitivity analysis and case study indicate that the model identifies how changes in individual monitoring parameters result in changes in overall ecosystem health, and thus illustrates its potential as a lake management tool.

Community well-being as a critical component of urban lake ecosystem health

Urban lakes are often monitored and managed with limited consideration of adjacent communities. Generally, when communities are considered in relation to urban lakes, they are viewed simply as sources of pollutants. Given the inevitable interactions between an urban lake and the surrounding inhabitants, the community must be considered explicitly when assessing the ecosystem health of urban lakes, as the two entities intrinsically comprise interrelated parts of a single ecosystem. In this study, the reciprocal links between a residential community and a series of urban lakes in South East Queensland have been examined to facilitate a dynamically linked, fully integrated ecosystem health assessment of constructed urban lakes. Residents’ attitudes towards, and values derived from, a series of urban lakes were surveyed, as well as residents’ behaviours which may impact upon urban lake health. The results indicate that residents derive both tangible and intangible benefits from the urban lakes, but feel little responsibility for lake health or custodianship over the lakes. Greater recognition within urban lake management frameworks of the links between urban lake systems and their surrounding communities may help to foster and enhance both community well-being, a greater sense of custodianship for such systems and improved management.

Host tree influences on longicorn beetle (Coleoptera: Cerambycidae) attack in subtropical Corymbia (Myrtales: Myrtaceae)

ABSTRACT Phoracantha longicorn beetles are endemic to Australia, and some species have become significant pests of eucalypts worldwide, yet little is known about their host plant interactions and factors influencing tree susceptibility in Australia. Here, we investigate the host relationships of Phoracantha solida (Blackburn, 1894) on four eucalypt taxa (one pure species and three hybrid families), examining feeding site physical characteristics including phloem thickness, density, and moisture content, and host tree factors such as diameter, height, growth, taper, and survival. We also determine the cardinal and vertical (within-tree) and horizontal (between-tree) spatial distribution of borers. Fewer than 10% of P. solida attacks were recorded from the pure species (Corymbia citriodora subsp. variegate (Hook)), and this taxon also showed the highest survival, phloem thickness, relative growth rate, and bark:wood area. For the two most susceptible taxa, borer severity was negatively correlated with moisture content, and positively related to phloem density. Borers were nonrandomly and nonuniformly distributed within trees, and were statistically aggregated in 32% of plots. More attacks were situated on the northern side of the tree than the other aspects, and most larvae fed within the lower 50 cm of the bole, with attack height positively correlated with severity. Trees with borers had more dead neighbors, and more bored neighbors, than trees without borers, while within plots, borer incidence and severity were positively correlated. Because the more susceptible taxa overlapped with less susceptible taxa for several physical tree factors, the role of primary and secondary chemistries in determining host suitability needs to be investigated. Nevertheless, taxon, moisture content, phloem density, tree size, and mortality of neighboring trees appeared the most important physical characteristics influencing host suitability for P. solida at this site.

Ecological implications of standard fire-mapping approaches for fire management of the World Heritage Area, Fraser Island, Australia

The characterisation of spatiotemporal fire patchiness is requisite for informing biodiversity conservation management in many landscape settings. Often, conservation managers are reliant on manually derived fire-history mapping products that delineate fire perimeters. An alternative standard approach concerns the application of remote sensing, typically using band combination indices obtained from relatively fine-scale imagery sensors. For Fraser Island, a World Heritage Area in subtropical, fire-prone eastern Australia, we contrast diagnostic fire-regime characteristics for differentvegetationtypesovera20-yearperiod(1989-2008)asderivedfromhistoricalmanual,andremotelysensed,fire- mapping approaches. For the remote sensing component we adapt a commonly used approach utilising a differenced normalised burn ratio (dNBR) index derived from Landsat Thematic Mapper imagery. Manual mapping resulted in overestimation of fire-affected area (especially large fires) and fire frequency, whereas the dNBR procedure resulted in underestimation of fire-affected area under low fire-severity conditions, and overestimation of fire patchiness. Of significance for conservation management, (1) age class and related distributions for flammable vegetation types differed markedly between the two mapping approaches, (2) regardless, both methods demonstrated that substantial fuel loads had accumulated in flammable vegetation types by the end of the study period and (3) fuel age was shown to have a more significant effect than did seasonality on the incidence of very large (.1000ha) fires. The study serves as an introduction to ongoing research concerning the measurement and application of fire patchiness to conservation management in flammable eastern Australian vegetation types. Additional keywords: dNBR, dry sclerophyll woodland, fire regime, NBR, patchiness, patch mosaic, wallum heath.

Molecular analysis of the Sydney rock oyster (Saccostrea glomerata) CO2 stress response

BackgroundHuman activities have led to a substantial increase in carbon dioxide (CO2) emission, with further increases predicted. A RNA-Seq study on adult Saccostrea glomerata was carried out to examine the molecular response of this bivalve species to elevated pCO2.ResultsA total of 1626 S. glomerata transcripts were found to be differentially expressed in oysters exposed to elevated pCO2 when compared to control oysters. These transcripts cover a range of functions, from immunity (e.g. pattern recognition receptors, antimicrobial peptides), to respiration (e.g. antioxidants, mitochondrial respiratory chain proteins) and biomineralisation (e.g. carbonic anhydrase). Overall, elevated levels of CO2 appear to have resulted in a priming of the immune system and in producing countermeasures to potential oxidative stress. CO2 exposure also seems to have resulted in an increase in the expression of proteins involved in protein synthesis, whereas transcripts putatively coding for proteins with a role in cilia and flagella function were down-regulated in response to the stressor. In addition, while some of the transcripts related to biomineralisation were up-regulated (e.g. carbonic anhydrase 2, alkaline phosphatase), a small group was down-regulated (e.g. perlucin).ConclusionsThis study highlighted the complex molecular response of the bivalve S. glomerata to expected near-future ocean acidification levels. While there are indications that the oyster attempted to adapt to the stressor, gauged by immune system priming and the increase in protein synthesis, some processes such cilia function appear to have been negatively affected by the elevated levels of CO2.