Population biology of the sand dollar, Peronella lesueuri, in Cockburn Sound, southwest Australia

Peronella lesueuri, commonly known as the pink sand dollar, is an irregular echinoid that can be found in the sandy sediment substrates of Cockburn Sound, southwest Australia. The numbers in which they are found indicate that they are likely to be an ecologically significant species. This is the first study of the biology and ecology of this species. A survey of current spatial distribution and abundances of Peronella lesueuri populations at a range of sites within Cockburn Sound shows the presence of the sand dollars on the shallower, sandy sills that surround the Sound. P. lesueuri was notably absent from the deeper central basin of Cockburn Sound, where silt is a major component of the sediment. The population densities of P. lesueuri ranged from 0.3 to 2.5 individuals m-2 at sites no deeper than ten metres. Mean test lengths were larger at sites less than five metres in depth. Sediment grain size preference and food availability were likely factors that determined the spatial distribution of the sand dollars in Cockburn Sound. Detailed monthly sampling for population demographics was conducted at Jervoise Bay over a 23-month period in which significant temporal variations in the densities of the P. lesueuri were recorded. Two spikes in population densities in December 2010 and January 2011 were indicative of clear annual recruitment events. The spike in densities caused by recruitment, however, were quick to return to what appeared to be the stable population density of 0.13 – 0.3 individuals m-2. This study showed that the P. lesueuri reproductive cycle is annual, with peak spawning in summer. Gametogenesis was recorded in spring, spawning in summer, spent gonads in autumn and gonads recovered during winter. The gametogenic cycle of P. lesueuri underwent five distinct morphological stages; Recovery, Growth, Mature, Partially Spawned and Spent, similar to those described in other echinoderm gametogenic cycles. In the recovery stage, nutritive phagocytes filled the lumen of both the testes and ovaries. Primary gametocytes (Stage 1 gametes) were present large numbers. Growing gonads contained increasing numbers of secondary gametocytes. Mature gametes are present in some gonads while nutritive phagocytes decreased in volume. In fully mature male gonads, lumens were densely packed with spermatozoa. Two variants of the mature stage were observed in the ovaries; one was packed full of ova with few oocytes, the other contained oocytes in all stages of development. Some female sand dollars produced only one cohort of ova which are spawned out once all the ova are released, while others can produce several cohorts of ova throughout the spawning period. Partially spawned gonads contained large numbers of mature gametes although spaces left by spawned gametes were observed. Lumens of spent gonads were mostly empty, although unspawned gametes in various stages of degeneration were occasionally present. Unspawned gametes eventually broke down and were incorporated into the nutritive phagocytes. The gametogenic stages were highly synchronous between sexes. Juveniles attained sexual maturity at between one and a half and two years of age. Size frequency distributions as well as density variation over a 23-month period indicated that Peronella lesueuri recruits annually. Juveniles appeared in the adult population around May/June, five to six months after the start of the spawning period. Annual recruitment strength was variable and juvenile mortality was high. Up to 88% juvenile mortality was measured in the first year alone. Pooled length-at-age data derived from the 2009 and 2010 cohorts of recruits was combined with length-at-age data for large “adult” sand dollars obtained from growth zone counts to construct a scatter plot to fit a growth curve. Growth in P. lesueuri is sigmoidal and is best described by the Richards’ Growth Curve. Juvenile P. lesueuri grow quickly, with a maximum growth rate of 60 mm yr-1 at two years of age. Intermediate-sized sand dollars were scarcely encountered. The rapid growth rate of sand dollars of intermediate size predicted by the Richards’ growth curve coupled with high juvenile mortality provides an explanation for the scarcity of sand dollars between 50 and 100 mm. The growth rate slowed to close to zero at approximately two and a half years of age, and this may be associated with the attainment of sexual maturity. Maximum size in the population studied was 182 mm. The maximum life expectancy is approximately five years. This study indicated that P. lesueuri has diurnal and seasonal patterns of activity throughout the year, with greater movement rates in summer (mean of 5.3 cm hr-1, day; 3.9 cm hr-1, night) than in the winter (mean of 2.7 cm hr-1, day; 2.0 cm hr-1, night). Seasonal changes in temperature and physiological requirements by the sand dollar are the most likely reason for the seasonal differences; however reasons for diurnal movement variation were unclear. Direction of movement was found to be random at both times of the year. Based on the movement rates, and at a density estimate of 0.5 sand dollars per m-2, it is estimated that the sand dollars can rework the entire area of the sediments in the habitats they occupy in approximately 20 days. This study provided the first histological description of the gametogenic cycle in Peronella lesueuri and established that the reproductive cycle is annual. The growth rate and life expectancy of P. lesueuri was also determined. The study of diurnal and seasonal patterns of activity in P. lesueuri indicated that it was ecologically significant as a sediment bioturbator. While further research is required to fully assess the biological and ecological significance of P. lesueuri in Cockburn Sound, the densities in which P. lesueuri is found on the shallow sediment bottoms imply that they have a potentially important role as an agent in mediating biogeochemical processes in the surface sediments

Risk factors for a post-operative neutrally aligned total knee arthroplasty in the sagittal plane developing fixed flexion deformity at 2 years follow up study

Background: The incidence of fixed flexion deformity (FFD) following total knee arthroplasty (TKA) has been reported to be as high as 17%, increasing demand on the quadriceps and hindering mobility. The aim of this study is then to identify these predictors for the development of FFD.Methods: In this retrospective study, all patients who underwent primary TKA from January 2008 to June 2009 at a single institution were identified. All patients with neutral alignment in the sagittal place of the knee intra-operatively were identified and followed up. The knee motion was measured in both operated and contralateral knees and followed-up for a minimum of 24 months post-operatively.Results: Multivariate analysis demonstrated pre-operative FFD of the non-operated knee (p-value 0.03), pre-operative range of motion of the operated knee (p-value 0.01) and non-operated (p-value 0.01) knee and pre-operative maximum flexion of the operated knee (p-value 0.001) to be independent risk factors for development of FFD at 24 months.Conclusions: Independent risk factors for the development of post-operative FFD in TKA are pre-operative FFD of the operated knee, FFD of the non-operated knee and the maximum flexion of the operated knee. The relative risk of a male developing FFD is also as high as 1.34

Physico-chemical properties of newly discovered hydrothermal plumes above the Southern Mid-Atlantic Ridge (13°-33°S)

Highlights • Hydrothermal survey in the 13°-33°S region of the Mid-Atlantic Ridge based on hydrographic casts, noble gas observations and AUV dives. • Discovery of hydrothermal plumes above ten ridge segments pointing to 14 unknown active vent sites. • Rio de Janeiro Transform (22°S) likely represents a barrier separating different vent endemic faunal communities to the north and south. Abstract The oceanic crust is initially cooled and deep-sea chemosynthetic ecosystems are largely fed by hydrothermal circulation and venting on the seafloor. Much of this venting takes place at mid-ocean ridges and in order to make realistic models of the crust's thermal budget and to understand chemosynthetic biogeography it is important to have a detailed inventory of vent sites. Until recently, a major gap in this inventory was the Mid-Atlantic Ridge south of 13°S, a key region for vent fauna biogeography as it is the corridor linking the Atlantic to the Indian and Pacific Oceans. In spring 2013 we systematically surveyed the axial region between 13°S and 33°S for hydrothermal signals in the water column, using turbidity, oxidation-reduction-potential (ORP) and noble gases as indicators. Standard conductivity-temperature-depth (CTD) rosette water-sampler deployments were complimented by a novel autonomous underwater vehicle (AUV) deployment strategy, in which the AUV made single-pass, segment-scale (up to 100 km long) dives close to the seafloor to detect small vents. The ca. 2100 km-long survey covered 16 ridge segments and we identified previously unknown hydrothermal plumes above ten segments that point to 14 new hydrothermal vent fields. The majority of plumes are located at high-relief segment centers, where magmatism is robust. A wide gap in the distribution of vents in the 19°S-23°S region coincides with the Rio de Janeiro Transform, the maximum southward progression of North Atlantic Deep Waters and the maximum northwards extent of 3He-enriched waters with Pacific origins. Crossflowing currents in the transform and the large gap between adjacent vents may prevent a meridional connection between the vent fauna communities in the North Atlantic and along the Antarctic Ridges. This makes the region a prime target for future biogeographical studies

Measuring oral health during pregnancy: Sensitivity and specificity of a maternal oral screening (MOS) tool

Background: Being the parent of a severely injured child involves many stressors throughout the trauma journey. Internationally, little is known about the experiences or levels of emotional distress, parenting stress, quality of life, and resilience for parents of injured children. The aim of this study is to investigate the experiences, unmet needs and outcomes of parents of physically injured children 0–12 years over the 2 year period following injury. Methods/design: This is a prospective longitudinal study using an embedded mixed methods design. This design has a primary qualitative strand which incorporates supplementary quantitative data on child quality of life, and parental quality of life, parenting stress, emotional distress, and resilience at four time points; the acute hospitalisation phase, and at 6, 12 and 24 months following injury. The primary sample are parents of injured children 0–12 years hospitalised in the Australian states of New South Wales, Queensland, Victoria and South Australia. Primary data sources are child and parent demographic data; survey data; and semi-structured interview data across a 24 month period. Discussion: This study aims to address the existing gap in knowledge on the experiences and unmet support needs of parents in the 2 years following child injury to provide guidance for care provision for these families. There is a lack of evidence-based recommendations for supporting parents and families of injured children and strengthening their capacity to address the challenges they face

Food Security : Threats and Challenges of Sustainable Paddy Production in Sarawak

Rice is a staple food in Malaysia, hence paddy farming is vital to Malaysian households. However, the total amount of local rice output is still insufficient to meet household demand. There are several areas in Sarawak that are excellent for agriculture, particularly paddy growing. To maximise productivity, this potential agricultural area had not yet been used to its full potential. This study aims to highlight the challenges and threats facing Sarawak's paddy cultivation. This study collects qualitative information and contrasts findings from Sarawak's rural and sub-urban paddy farming. Interviews with 30 farmers were done in the sub-urban areas of Lundu and Siburan as well as the rural production areas of Bario and Long Seridan. Thematic analysis has been used to analyse the data. The results show that threats to and challenges to the sustainable production of the paddy sector include subsidies, a lack of understanding of the enhancement programme, a lack of communication channels to inform about production issues, a lack of marketing channels for the products, and other problems like price, ageing factors, and others. In the study, some suggestions for improving the sector will be found

Hydrothermal Activity and Seismicity at Teahitia Seamount: Reactivation of the Society Islands Hotspot?

Along mid-ocean ridges, submarine venting has been found at all spreading rates and in every ocean basin. By contrast, intraplate hydrothermal activity has only been reported from five locations, worldwide. Here we extend the time series at one of those sites, Teahitia Seamount, which was first shown to be hydrothermally active in 1983 but had not been revisited since 1999. Previously, submersible investigations had led to the discovery of low-temperature (≤30°C) venting associated with the summit of Teahitia Seamount at ≤1500 m. In December 2013 we returned to the same site at the culmination of the US GEOTRACES Eastern South Tropical Pacific (GP16) transect and found evidence for ongoing venting in the form of a non-buoyant hydrothermal plume at a depth of 1400 m. Multi-beam mapping revealed the same composite volcano morphology described previously for Teahitia including four prominent cones. The plume overlying the summit showed distinct in situ optical backscatter and redox anomalies, coupled with high concentrations of total dissolvable Fe (≤186 nmol/L) and Mn (≤33 nmol/L) that are all diagnostic of venting at the underlying seafloor. Continuous seismic records from 1986-present reveal a ∼15 year period of quiescence at Teahitia, following the seismic crisis that first stimulated its submersible-led investigation. Since 2007, however, the frequency of seismicity at Teahitia, coupled with the low magnitude of those events, are suggestive of magmatic reactivation. Separately, distinct seismicity at the adjacent Rocard seamount has also been attributed to submarine extrusive volcanism in 2011 and in 2013. Theoretical modeling of the hydrothermal plume signals detected suggest a minimum heat flux of 10 MW at the summit of Teahitia. Those model simulations can only be sourced from an area of low-temperature venting such as that originally reported from Teahitia if the temperature of the fluids exiting the seabed has increased significantly, from ≤30°C to ∼70°C. These model seafloor temperatures and our direct plume observations are both consistent with reports from Loihi Seamount, Hawaii, ∼10 year following an episode of seafloor volcanism. We hypothesize that the Society Islands hotspot may be undergoing a similar episode of both magmatic and hydrothermal reactivation

Functional heterogeneity of POMC neurons relies on mTORC1 signaling.

Hypothalamic pro-opiomelanocortin (POMC) neurons are known to trigger satiety. However, these neuronal cells encompass heterogeneous subpopulations that release γ-aminobutyric acid (GABA), glutamate, or both neurotransmitters, whose functions are poorly defined. Using conditional mutagenesis and chemogenetics, we show that blockade of the energy sensor mechanistic target of rapamycin complex 1 (mTORC1) in POMC neurons causes hyperphagia by mimicking a cellular negative energy state. This is associated with decreased POMC-derived anorexigenic α-melanocyte-stimulating hormone and recruitment of POMC/GABAergic neurotransmission, which is restrained by cannabinoid type 1 receptor signaling. Electrophysiology and optogenetic studies further reveal that pharmacological blockade of mTORC1 simultaneously activates POMC/GABAergic neurons and inhibits POMC/glutamatergic ones, implying that the functional specificity of these subpopulations relies on mTORC1 activity. Finally, POMC neurons with different neurotransmitter profiles possess specific molecular signatures and spatial distribution. Altogether, these findings suggest that mTORC1 orchestrates the activity of distinct POMC neurons subpopulations to regulate feeding behavior

In silico identification of two peptides with antibacterial activity against multidrug-resistant Staphylococcus aureus

Here we report two antimicrobial peptides (AMPs), HG2 and HG4 identified from a rumen microbiome metagenomic dataset, with activity against multidrug-resistant (MDR) bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA) strains, a major hospital and community-acquired pathogen. We employed the classifier model design to analyse, visualise, and interpret AMP activities. This approach allowed in silico discrimination of promising lead AMP candidates for experimental evaluation. The lead AMPs, HG2 and HG4, are fast-acting and show anti-biofilm and anti-inflammatory activities in vitro and demonstrated little toxicity to human primary cell lines. The peptides were effective in vivo within a Galleria mellonella model of MRSA USA300 infection. In terms of mechanism of action, HG2 and HG4 appear to interact with the cytoplasmic membrane of target cells and may inhibit other cellular processes, whilst preferentially binding to bacterial lipids over human cell lipids. Therefore, these AMPs may offer additional therapeutic templates for MDR bacterial infections

In silico identification of two peptides with antibacterial activity against multidrug-resistant Staphylococcus aureus

Here we report two antimicrobial peptides (AMPs), HG2 and HG4 identified from a rumen microbiome metagenomic dataset, with activity against multidrug-resistant (MDR) bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA) strains, a major hospital and community-acquired pathogen. We employed the classifier model design to analyse, visualise, and interpret AMP activities. This approach allowed in silico discrimination of promising lead AMP candidates for experimental evaluation. The lead AMPs, HG2 and HG4, are fast-acting and show anti-biofilm and anti-inflammatory activities in vitro and demonstrated little toxicity to human primary cell lines. The peptides were effective in vivo within a Galleria mellonella model of MRSA USA300 infection. In terms of mechanism of action, HG2 and HG4 appear to interact with the cytoplasmic membrane of target cells and may inhibit other cellular processes, whilst preferentially binding to bacterial lipids over human cell lipids. Therefore, these AMPs may offer additional therapeutic templates for MDR bacterial infections