scholarly journals Multiple factors likely explain variation in investment in sexual reproduction by lake Daphnia populations

2021 ◽  
Author(s):  
Camden Gowler ◽  
Mary Rogalski ◽  
Clara Shaw ◽  
Katherine Hunsberger ◽  
Meghan Duffy
Keyword(s):  
Sexual Reproduction ◽  
Light Attenuation ◽  
Host Density ◽  
Multiple Factors ◽  
Time Series Dataset ◽  
Parasite Infections ◽  
Dominant Member ◽  
Cyclical Parthenogens ◽  
Daphnia Dentifera ◽  
Do So

Many organisms can reproduce both asexually and sexually. For cyclical parthenogens, periods of asexual reproduction are punctuated by bouts of sexual reproduction, and the timing of the shift from asexual to sexual reproduction has large impacts on fitness and population dynamics. We studied populations of Daphnia dentifera to determine the amount of investment in sexual reproduction as well as the factors associated with variation in investment in sex. To do so, we tracked host density, parasite infections, sexual reproduction, temperature, and light attenuation in 15 lake populations of D. dentifera for three years. We monitored infections by nine common parasites; this is notable since most prior studies on investment in sex and parasitism have focused on a single parasite, even though multiparasite communities are the norm in nature. We found substantial variation in investment in sex, with some populations reproducing entirely asexually throughout the study period and others shifting almost entirely to sexual reproduction by late autumn. We found that higher host density and parasitism were associated with greater investment in sex. Temperature and light attenuation were not as predictive of investment in sex, but received some statistical support. While correlational, our results leverage a large time series dataset and suggest multiple factors likely drive variation in sexual reproduction in this dominant member of lake food webs.

scholarly journals Density, parasitism, and sexual reproduction are strongly correlated in lake Daphnia populations

2021 ◽  
Author(s):  
Camden Gowler ◽  
Mary Rogalski ◽  
Clara Shaw ◽  
Katherine Hunsberger ◽  
Meghan Duffy
Keyword(s):  
Species Richness ◽  
Sexual Reproduction ◽  
Parasite Species ◽  
Host Density ◽  
Strongly Correlated ◽  
Substantial Variation ◽  
Factors Associated ◽  
Cyclical Parthenogens ◽  
Daphnia Dentifera ◽  
Do So

Many organisms can reproduce both asexually and sexually. For cyclical parthenogens, periods of asexual reproduction are punctuated by bouts of sexual reproduction, and the shift from asexual to sexual reproduction has large impacts on fitness and population dynamics. We studied populations of Daphnia dentifera to determine the amount of investment in sexual reproduction as well as the factors associated with variation in investment in sex. To do so, we tracked host density, infections by nine different parasites, and sexual reproduction in 15 lake populations of D. dentifera for three years. Sexual reproduction was seasonal, with male and ephippial female production beginning as early as late September and generally increasing through November. However, there was substantial variation in the prevalence of sexual individuals across populations, with some populations remaining entirely asexual throughout the study period and others shifting almost entirely to sexual females and males. We found strong relationships between density, prevalence of infection, parasite species richness, and sexual reproduction in these populations. However, strong collinearity between density, parasitism, and sexual reproduction means that further work will be required to disentangle the causal mechanisms underlying these relationships.

scholarly journals Last-come, best served? Mosquito biting order and Plasmodium transmission

2020 ◽  
Vol 287 (1939) ◽  
pp. 20202615
Author(s):  
J. Isaïa ◽  
A. Rivero ◽  
O. Glaizot ◽  
P. Christe ◽  
R. Pigeault
Keyword(s):  
Host Population ◽  
Environmental Stochasticity ◽  
Parasite Transmission ◽  
Temporal Heterogeneity ◽  
Mosquito Vectors ◽  
Plastic Response ◽  
Multiple Factors ◽  
Parasite Infections ◽  
Underlying Mechanisms ◽  
Plasmodium Transmission

A pervasive characteristic of parasite infections is their tendency to be overdispersed. Understanding the mechanisms underlying this overdispersed distribution is of key importance as it may impact the transmission dynamics of the pathogen. Although multiple factors ranging from environmental stochasticity to inter-individual heterogeneity may explain parasite overdispersion, parasite infection is also overdispersed in an inbred host population maintained under laboratory conditions, suggesting that other mechanisms are at play. Here, we show that the aggregated distribution of malaria parasites within mosquito vectors is partially explained by a temporal heterogeneity in parasite infectivity triggered by the bites of mosquitoes. Parasite transmission tripled between the mosquito's first and last blood feed in a period of only 3 h. Surprisingly, the increase in transmission is not associated with an increase in parasite investment in production of the transmissible stage. Overall, we highlight that Plasmodium is capable of responding to the bites of mosquitoes to increase its own transmission at a much faster pace than initially thought and that this is partly responsible for overdispersed distribution of infection. We discuss the underlying mechanisms as well as the broader implications of this plastic response for the epidemiology of malaria.

The prevalence of avian Plasmodium is higher in undisturbed tropical forests of Cameroon

2009 ◽  
Vol 25 (4) ◽  
pp. 439-447 ◽  
Author(s):  
Camille Bonneaud ◽  
Irem Sepil ◽  
Borja Milá ◽  
Wolfgang Buermann ◽  
John Pollinger ◽  
...  
Keyword(s):  
Rain Forest ◽  
Forest Type ◽  
Natural Populations ◽  
Host Density ◽  
Parasite Prevalence ◽  
Haemosporidian Parasites ◽  
Habitat Differences ◽  
Parasite Infections ◽  
Host Parasite ◽  
Avian Plasmodium

Abstract:Habitat fragmentation and deforestation are thought to disrupt host–parasite interactions and increase the risk of epizootic outbreaks in wild vertebrates. A total of 220 individuals from three species of African rain-forest bird (Andropadus latirostris, Andropadus virens, Cyanomitra obscura), captured in two pristine and two agroforests in Cameroon, were screened for the presence of avian haemosporidian parasites (species of Plasmodium and Haemoproteus) to test whether habitat differences were associated with differences in the prevalence of infectious diseases in natural populations. Thirteen mitochondrial lineages, including 11 Plasmodium and two Haemoproteus lineages were identified. Whereas levels of Haemoproteus spp. infections were too low to permit analysis, the prevalence of infections with Plasmodium spp. reached significantly greater levels in undisturbed mature forests. Importantly however, the significant association between forest type and parasite prevalence was independent of host density effects, suggesting that the association did not reflect changes in host species composition and abundance between forest types. Our results illustrate how characterizing land-cover differences, and hence changes, may be a prerequisite to understanding and predicting patterns of parasite infections in natural populations of rain-forest birds.

scholarly journals Role of Increasing Levels of Non-Performing Assets in Bank’s Deteriorating Financial Position After COVID: A Review of Literature

2021 ◽  
Author(s):  
Prasanth Selvam ◽  
S Sudhamathi
Keyword(s):  
Bank Failures ◽  
Review Of Literature ◽  
Indian Government ◽  
Multiple Factors ◽  
Financial Position ◽  
Reserve Bank ◽  
Reserve Bank Of India ◽  
Do So ◽  
Leading Journals

After the 2009 planet-wide crisis, Non-Performing Assets (NPA) have seen an unprecedented rise. Along with the Indian Government, the Reserve Bank of India (RBI) introduced rules and provided guidelines to control the increasing amount of NPA, but failed to do so. The ever - NPA level has contributed to a decline in the bank's revenue and profitability level, adding further to its failures. The report contains an analysis of literature published by renowned scholars on rising NPA and bank failures. The report provides an overview of the diverse perspectives of experts and regulators. It reviews a total of 105 academic papers published in leading journals. The key aim of the report is to address the multiple factors instigating the NPA's growing degree. It also discusses the role of these factors in the failure of the numerous banks following Covid 19. It is undisputed that the journey to recovery is incredibly long, but the study proposes steps to control and decrease increasing NPA levels that can be taken.

Heeding the Sirens: The Politics of IMF Program Participation

2014 ◽  
Vol 3 (1) ◽  
pp. 73-93 ◽  
Author(s):  
Irfan Nooruddin ◽  
Byungwon Woo
Keyword(s):  
Economic Crisis ◽  
Domestic Politics ◽  
Program Participation ◽  
Economic Distress ◽  
Political Incentives ◽  
Political Determinants ◽  
Time Series Dataset ◽  
Regime Types ◽  
Imf Programs ◽  
Do So

Given similar economic distress indicators, why do some states enter into International Monetary Fund (IMF) programs while others do not? Building on extant studies of IMF program participation that highlight the importance of various economic and political determinants, this article proposes an argument focusing on the political incentives of the IMF and a borrowing country when they engage in IMF program negotiations. Specifically, the study develops a domestic politics argument to highlight the interactions among sovereignty costs, competence costs, economic conditions and domestic regime types, and tests the argument using a cross-national time-series dataset of all IMF agreements between 1970 and 2006. It finds that when the economic crisis is mild, democracies are less likely than non-democracies to enter IMF programs, but that when the economic crisis is severe, democracies are more likely to do so than their autocratic counterparts. The article attributes this tendency to democratic leaders’ electoral vulnerability and shows that these patterns become more pronounced as elections draw near.

Infections by the trematode Microphallus nicolli and the acanthocephalan Profilicollis altmani in relation to the reproductive condition of their intermediate host, the Pacific mole crab Emerita analoga

2020 ◽  
Vol 70 (4) ◽  
pp. 417-425
Author(s):  
Ritindra N. Bhaduri
Keyword(s):  
Host Species ◽  
Egg Production ◽  
Carapace Length ◽  
Parasite Prevalence ◽  
Reproductive State ◽  
Reproductive Condition ◽  
Emerita Analoga ◽  
The Pacific ◽  
Parasite Infections ◽  
Do So

Abstract Parasites can dramatically influence fecundity of their hosts, so for any host species it is important to establish whether parasite infections affect host reproduction. The Pacific mole crab, Emerita analoga, commonly harbors metacercarial cysts of the trematode Microphallus nicolli and cystacanths of the acanthocephalan Profilicollis altmani. Although these helminths are known to infect primarily larger female mole crabs, they may do so disproportionately when tied to their host’s reproductive condition. This study was undertaken to examine differences in parasite prevalence and abundance between non-ovigerous and ovigerous hosts. Crabs from Del Monte Beach, Monterey, California were collected, carapace length measured, sexed, examined for parasites, and had their reproductive state noted. The vast majority of the crabs sampled were infected with at least one parasite, and over half of the crabs had both M. nicolli and P. altmani. Ovigerous females were significantly larger than non-ovigerous crabs. Prevalence of both trematode metacercarial cysts and acanthocephalan cystacanths was significantly higher in ovigerous females than in non-ovigerous ones. Egg-bearing females were also more heavily infected by both parasites than non-egg-bearing individuals. These results suggest that larger ovigerous crabs may provide greater resources and thus are able to support higher levels of infections. This study shows that neither parasite prevalence nor abundance seemed to affect egg production in E. analoga.

Holding replication studies to mainstream standards of evidence

2018 ◽  
Vol 41 ◽  
Author(s):  
Duane T. Wegener ◽  
Leandre R. Fabrigar
Keyword(s):  
Replication Studies ◽  
Replication Research ◽  
Standards Of Evidence ◽  
Do So

AbstractReplications can make theoretical contributions, but are unlikely to do so if their findings are open to multiple interpretations (especially violations of psychometric invariance). Thus, just as studies demonstrating novel effects are often expected to empirically evaluate competing explanations, replications should be held to similar standards. Unfortunately, this is rarely done, thereby undermining the value of replication research.

Electron Microscopy of a Herpesvirus Isolated from Marek's Disease in Duck and Chicken Embryo Fibroblast Cultures

1968 ◽  
Vol 26 ◽  
pp. 222-223 ◽  
Author(s):  
Keyvan Nazerian
Keyword(s):  
Inclusion Bodies ◽  
Chicken Embryo Fibroblast ◽  
Marek's Disease ◽  
Marek’S Disease ◽  
Duck Embryo Fibroblast ◽  
Multinucleated Cells ◽  
Viral Particles ◽  
Infected Cells ◽  
And Control ◽  
Do So

A herpes-like virus has been isolated from duck embryo fibroblast (DEF) cultures inoculated with blood from Marek's disease (MD) infected birds. Cultures which contained this virus produced MD in susceptible chickens while virus negative cultures and control cultures failed to do so. This and other circumstantial evidence including similarities in properties of the virus and the MD agent implicate this virus in the etiology of MD.Histochemical studies demonstrated the presence of DNA-staining intranuclear inclusion bodies in polykarocytes in infected cultures. Distinct nucleo-plasmic aggregates were also seen in sections of similar multinucleated cells examined with the electron microscope. These aggregates are probably the same as the inclusion bodies seen with the light microscope. Naked viral particles were observed in the nucleus of infected cells within or on the edges of the nucleoplasmic aggregates. These particles measured 95-100mμ, in diameter and rarely escaped into the cytoplasm or nuclear vesicles by budding through the nuclear membrane (Fig. 1). The enveloped particles (Fig. 2) formed in this manner measured 150-170mμ in diameter and always had a densely stained nucleoid. The virus in supernatant fluids consisted of naked capsids with 162 hollow, cylindrical capsomeres (Fig. 3). Enveloped particles were not seen in such preparations.

Debates in Dysphagia Management: How Do You Use Evidence-Based Practice in Your Dysphagia Patient Care?

2011 ◽  
Vol 20 (4) ◽  
pp. 121-123
Author(s):  
Jeri A. Logemann
Keyword(s):  
Decision Making ◽  
Patient Care ◽  
Clinical Outcomes ◽  
Clinical Judgment ◽  
Clinical Decision Making ◽  
Evidence Based Practice ◽  
Clinical Decision ◽  
Evidence Based ◽  
Clinical Method ◽  
Do So

Evidence-based practice requires astute clinicians to blend our best clinical judgment with the best available external evidence and the patient's own values and expectations. Sometimes, we value one more than another during clinical decision-making, though it is never wise to do so, and sometimes other factors that we are unaware of produce unanticipated clinical outcomes. Sometimes, we feel very strongly about one clinical method or another, and hopefully that belief is founded in evidence. Some beliefs, however, are not founded in evidence. The sound use of evidence is the best way to navigate the debates within our field of practice.

Case Exercise: Biomechanics in Rearend Motor Vehicle Collisions

2007 ◽  
Vol 12 (3) ◽  
pp. 4-7
Author(s):  
Charles N. Brooks ◽  
Christopher R. Brigham
Keyword(s):  
Motor Vehicle ◽  
Body Position ◽  
Motor Vehicle Collisions ◽  
Time Curve ◽  
Vehicle Collisions ◽  
Need For Treatment ◽  
Multiple Factors ◽  
Bodily Injury ◽  
Vehicle Collision ◽  
Physical Findings

Abstract Multiple factors determine the likelihood, type, and severity of bodily injury following a motor vehicle collision and, in turn, influence the need for treatment, extent of disability, and likelihood of permanent impairment. Among the most important factors is the change in velocity due to an impact (Δv). Other factors include the individual's strength and elasticity, body position at the time of impact, awareness of the impending impact (ie, opportunity to brace, guard, or contract muscles before an impact), and effects of braking. Because Δv is the area under the acceleration vs time curve, it combines force and duration and is a useful way to quantify impact severity. The article includes a table showing the results of a literature review that concluded, “the consensus of human subject research conducted to date is that a single exposure to a rear-end impact with a Δv of 5 mph or less is unlikely to result in injury” in most healthy, restrained occupants. Because velocity incorporates direction as well as speed, a vehicular occupant is less likely to be injured in a rear impact than when struck from the side. Evaluators must consider multiple factors, including the occupant's pre-existing physical and psychosocial status, the mechanism and magnitude of the collision, and a variety of biomechanical variables. Recommendations based solely on patient history and physical findings (and, perhaps, imaging studies) may be ill-informed.

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