Parasite mediated selection, sex and diapause in a natural population of Daphnia

Parasites are thought to have large effects on their host populations, driving genetic change, population density changes, speciation and be a major selective force maintaining sexual reproduction. Indirect signatures of parasite-mediated selection are common, but explicit examples of parasite-mediated selection in nature are lacking. In this thesis I examine parasite-mediated dynamics in a natural population of Daphnia magna that experiences an annual epidemic of the bacterial pathogen Pasteuria ramosa. I also test a novel hypothesis investigating the relationship between parasitism and the production of resting eggs. In chapter 2 a combined field study and laboratory infection experiment illustrates one of the best examples of parasite-mediated selection in a natural population, with Daphnia collected after a parasite epidemic having higher levels of parasite resistance than those collected before. This chapter also explored the relationship between parasitism and resting eggs, which are only produced during the sexual phase of reproduction. Daphnia that were reproducing sexually in the field prior to the parasite epidemic were more susceptible, supporting higher levels of parasite growth, than their asexual counterparts. This supports the idea that some genotypes invest in sex at the expense of parasite resistance. In chapter 3 I used molecular markers to investigate genotype frequency changes in the same population in relation to the parasite epidemic. The parasite epidemic was found to be associated with genetic change in the population, and a laboratory infection experiment revealed that the genotype most resistant to the parasite was also most common following the peak of the parasite epidemic. While chapter 2 explored a genetic relationship between susceptibility and resting eggs, chapter 4 explores whether crowding conditions, cues indicating parasite prevalence in the population, or direct exposure to parasite spores can induce resting egg production. I found that crowding conditions or parasite prevalence enhance levels of male and resting egg production, but patterns were entirely dependent on Daphnia genotypes. There was no indication that exposure to parasite spores affects levels of sexual reproduction

Density-and trait-mediated effects of a parasite and a predator in a tri-trophic food web

1. Despite growing interest in ecological consequences of parasitism in food webs, relatively little is known about effects of parasites on long-term population dynamics of non-host species or about whether such effects are density- or trait- mediated. 2. We studied a tri-trophic food chain comprised of: (i) a bacterial basal resource (Serratia fonticola), (ii) an intermediate consumer (Paramecium caudatum), (iii) a top predator (Didinium nasutum), and (iv) a parasite of the intermediate consumer (Holospora undulata). A fully-factorial experimental manipulation of predator and parasite presence/absence was combined with analyses of population dynamics, modelling, and analyses of host (Paramecium) morphology and behavior. 3. Predation and parasitism each reduced the abundance of the intermediate consumer (Paramecium), and parasitism indirectly reduced the abundance of the basal resource (Serratia). However, in combination, predation and parasitism had non-additive effects on the abundance of the intermediate consumer, as well as on that of the basal resource. In both cases, the negative effect of parasitism seemed to be effaced by predation. 4. Infection of the intermediate consumer reduced predator abundance. Modelling and additional experimentation revealed that this was most likely due to parasite reduction of intermediate host abundance (a density-mediated effect), as opposed to changes in predator functional or numerical response. 5. Parasitism altered morphological and behavioural traits, by reducing host cell length and increasing the swimming speed of cells with moderate parasite loads. Additional tests showed no significant difference in Didinium feeding rate on infected and uninfected hosts, suggesting that the combination of these modifications does not affect host vulnerability to predation. However, estimated rates of encounter with Serratia based on these modifications were higher for infected Paramecium than for uninfected Paramecium. 6. A mixture of density-mediated and trait-mediated indirect effects of parasitism on non- host species creates rich and complex possibilities for effects of parasites in food webs that should be included in assessments of possible impacts of parasite eradication or introduction

Intraspecific variation for host immune activation by the spider mite Tetranychus evansi

Many parasites can interfere with their host’s defences tomaximize their fitness. Here, we investigated if there isheritable variation in the spider miteTetranychus evansifortraits associated with how they interact with their host plant.We also determined if this variation correlates with mitefecundity.Tetranychus evansican interfere with jasmonate (JA)defences which are the main determinant of anti-herbivoreimmunity in plants. We investigated (i) variation in fecundityin the presence and absence of JA defences, making use ofa wild-type tomato cultivar and a JA-deficient mutant(defenseless-1), and (ii) variation in the induction of JAdefences, in fourT. evansifield populations and 59 inbredlines created from an outbred population originating fromcontrolled crosses of the four field populations. We observed astrong positive genetic correlation between fecundity in thepresence (on wild-type) and the absence of JA defences (ondefenseless-1). However, fecundity did not correlate with themagnitude of induced JA defences in wild-type plants. Ourresults suggest that the performance of the specialistT. evansiis not related to their ability to manipulate plant defences,either because all lines can adequately reduce levels ofdefences, or because they are resistant to them.info:eu-repo/semantics/publishedVersio

Supporting weight management services during the COVID-19 pandemic: Phase I insights

Societal changes required to manage the coronavirus (COVID-19) pandemic may have inadvertently promoted weight gain, due to the adverse impact on socio-economics, psychological health, and the resulting metabolic impact of elevated stress, emotional eating and physical inactivity. Evidence on the impact of COVID-19 has rapidly accumulated, to demonstrate that people living with obesity are at higher risk of severe illness from COVID-19 infection. It is therefore important to understand what is happening in terms of weight management practice to develop local and national thinking. This project will explore the impact of the COVID-19 upon the provision of tier 2 and 3 weight management services (WMS) in England during the lockdown period (phase I; March-June 2020); and determine what needs to happen in the future (phase II; September-November 2020). This report documents findings from phase I

Initial evaluation of nighttime restlessness in a naturally occurring canine model of osteoarthritis pain

Chronic pain due to osteoarthritis (OA) can lead to significant disruption of sleep and increased restlessness. Our objective was to assess whether naturally occurring canine OA is associated with nighttime restlessness and so has potential as a model of OA-associated sleep disturbance. The study was designed as a two-part prospective masked, placebo-controlled study using client-owned dogs (Part A n = 60; Part B n = 19). Inclusion criteria consisted of OA-associated joint pain and mobility impairment. The primary outcome measure for both parts was nighttime accelerometry. In Part B, quality of sleep was assessed using a clinical metrology instrument (Sleep and Night Time Restlessness Evaluation Score, SNoRE). Part A included dogs receiving two weeks of non-steroidal anti-inflammatory drug (NSAID) preceded with two weeks of no treatment. Part B was a crossover study, with NSAID/placebo administered for two weeks followed by a washout period of one week and another two weeks of NSAID/placebo. Repeated measures analysis of variance was used to assess differences between baseline and treatment. There were no significant changes in accelerometry-measured nighttime activity as a result of NSAID administration. SNoRE measures indicated significant improvements in aspects of the quality of nighttime sleep that did not involve obvious movement. These results reflect the few similar studies in human OA patients. Although accelerometry does not appear to be useful, this model has potential to model the human pain-related nighttime sleep disturbance, and other outcome measures should be explored in this model

Sex ratios in the rodent malaria parasite, Plasmodium chabaudi

The sex ratios of malaria and related Apicomplexan parasites play a major role in transmission success. Here, we address 2 fundamental issues in the sex ratios of the rodent malaria parasite, Plasmodium chabaudi. First we test the accuracy of empirical methods for estimating sex ratios in malaria parasites, and show that sex ratios made with standard thin smears may overestimate the proportion of female gametocytes. Secondly, we test whether the mortality rate differs between male and female gametocytes, as assumed by sex ratio theory. Conventional application of sex ratio theory to malaria parasites assumes that the primary sex ratio can be accurately determined from mature gametocytes circulating in the peripheral circulation. We stopped gametocyte production with chloroquine in order to study a cohort of gametocytes in vitro. The mortality rate was significantly higher for female gametocytes, with an average half-life of 8 h for female gametocytes and 16 h for male gametocytes

FOXP2-positive diffuse large B-cell lymphomas exhibit a poor response to R-CHOP therapy and distinct biological signatures.

FOXP2 shares partially overlapping normal tissue expression and functionality with FOXP1; an established diffuse large B-cell lymphoma (DLBCL) oncogene and marker of poor prognosis. FOXP2 is expressed in the plasma cell malignancy multiple myeloma but has not been studied in DLBCL, where a poor prognosis activated B-cell (ABC)-like subtype display partially blocked plasma cell differentiation. FOXP2 protein expression was detected in ABC-DLBCL cell lines, and in primary DLBCL samples tumoral FOXP2 protein expression was detected in both germinal center B-cell-like (GCB) and non-GCB DLBCL. In biopsies from DLBCL patients treated with immunochemotherapy (R-CHOP), ≥ 20% nuclear tumoral FOXP2-positivity (n = 24/158) correlated with significantly inferior overall survival (OS: P = 0.0017) and progression-free survival (PFS: P = 0.0096). This remained significant in multivariate analysis against either the international prognostic index score or the non-GCB DLBCL phenotype (P < 0.05 for both OS and PFS). Expression of BLIMP1, a marker of plasmacytic differentiation that is commonly inactivated in ABC-DLBCL, did not correlate with patient outcome or FOXP2 expression in this series. Increased frequency of FOXP2 expression significantly correlated with FOXP1-positivity (P = 0.0187), and FOXP1 co-immunoprecipitated FOXP2 from ABC-DLBCL cells indicating that these proteins can co-localize in a multi-protein complex. FOXP2-positive DLBCL had reduced expression of HIP1R (P = 0.0348), which is directly repressed by FOXP1, and exhibited distinct patterns of gene expression. Specifically in ABC-DLBCL these were associated with lower expression of immune response and T-cell receptor signaling pathways. Further studies are warranted to investigate the potential functional cooperativity between FOXP1 and FOXP2 in repressing immune responses during the pathogenesis of high-risk DLBCL

Baseline and longitudinal grey matter changes in newly diagnosed Parkinson\u27s disease: ICICLE-PD study

Mild cognitive impairment in Parkinson\u27s disease is associated with progression to dementia (Parkinson\u27s disease dementia) in a majority of patients. Determining structural imaging biomarkers associated with prodromal Parkinson\u27s disease dementia may allow for the earlier identification of those at risk, and allow for targeted disease modifying therapies. One hundred and five non-demented subjects with newly diagnosed idiopathic Parkinson\u27s disease and 37 healthy matched controls had serial 3 T structural magnetic resonance imaging scans with clinical and neuropsychological assessments at baseline, which were repeated after 18 months. The Movement Disorder Society Task Force criteria were used to classify the Parkinson\u27s disease subjects into Parkinson\u27s disease with mild cognitive impairment (n = 39) and Parkinson\u27s disease with no cognitive impairment (n = 66). Freesurfer image processing software was used to measure cortical thickness and subcortical volumes at baseline and follow-up. We compared regional percentage change of cortical thinning and subcortical atrophy over 18 months. At baseline, cases with Parkinson\u27s disease with mild cognitive impairment demonstrated widespread cortical thinning relative to controls and atrophy of the nucleus accumbens compared to both controls and subjects with Parkinson\u27s disease with no cognitive impairment. Regional cortical thickness at baseline was correlated with global cognition in the combined Parkinson\u27s disease cohort. Over 18 months, patients with Parkinson\u27s disease with mild cognitive impairment demonstrated more severe cortical thinning in frontal and temporo-parietal cortices, including hippocampal atrophy, relative to those with Parkinson\u27s disease and no cognitive impairment and healthy controls, whereas subjects with Parkinson\u27s disease and no cognitive impairment showed more severe frontal cortical thinning compared to healthy controls. At baseline, Parkinson\u27s disease with no cognitive impairment converters showed bilateral temporal cortex thinning relative to the Parkinson\u27s disease with no cognitive impairment stable subjects. Although loss of both cortical and subcortical volume occurs in non-demented Parkinson\u27s disease, our longitudinal analyses revealed that Parkinson\u27s disease with mild cognitive impairment shows more extensive atrophy and greater percentage of cortical thinning compared to Parkinson\u27s disease with no cognitive impairment. In particular, an extension of cortical thinning in the temporo-parietal regions in addition to frontal atrophy could be a biomarker in therapeutic studies of mild cognitive impairment in Parkinson\u27s disease for progression towards dementia

Causes and consequences of dispersal in biodiverse spatially structured systems: what is old and what is new?

Dispersal is a well recognized driver of ecological and evolutionary dynamics, and simultaneously an evolving trait. Dispersal evolution has traditionally been studied in single-species metapopulations so that it remains unclear how dispersal evolves in spatially structured communities and food webs. Since most natural systems are biodiverse and spatially structured, and thus affected by dispersal and its evolution, this knowledge gap should be bridged. Here we discuss whether knowledge established in single-species systems holds in spatially structured multispecies systems and highlight generally valid and fundamental principles. Most biotic interactions form the ecological theatre for the evolutionary dispersal play because interactions mediate patterns of fitness expectations in space and time. While this allows for a simple transposition of certain known drivers to a multispecies context, other drivers may require more complex transpositions, or might not be transferred. We discuss an important quantitative modulator of dispersal evolution in the increased trait dimensionality of biodiverse meta-systems and an additional driver in co-dispersal. We speculate that scale and selection pressure mismatches due to co-dispersal, together with increased trait dimensionality may lead to slower and more "diffuse" evolution in biodiverse meta-systems. Open questions and potential consequences in both ecological and evolutionary terms call for more investigation