Weather and the Success of Parasites in Population Regulation

1965 ◽  
Vol 97 (8) ◽  
pp. 848-863 ◽  
Author(s):  
Paul DeBach
Keyword(s):  
Population Regulation ◽  
Host Population ◽  
Population Increase ◽  
Population Densities ◽  
Upper Limits ◽  
Desert Areas ◽  
Low Levels ◽  
Favorable Weather ◽  
Host Parasite ◽  
Parasite Complex

AbstractExamples and data based on the host-parasite complex of the California red scale, Aonidiella aurantii (Maskell), and its parasites in untreated test plots in the citrus areas of southern California, not including the San Joaquin Valley and the desert areas, show the following: (1) Weather does not impose upper limits to host population increase. (2) In areas of favorable weather, certain parasites regulate host population densities at very low levels, other factors also being favorable. (3) The parasite Aphytis lingnanensis Compere is affected by weather differentially with respect to the host, and to varying degrees in different localities. The effects of field weather for each 2-week period of the year on all stages of this parasite individually as well as on population growth in held experimental cages are discussed. Adverse effects of weather on the parasite preclude successful population regulation of the host by the parasite at certain times or in particular areas but the range of the parasite is not restricted. (4) Another parasite, Comperiella bifasciata Howard, has its range restricted by weather and not by competition with other parasites to intermediate and interior citrus growing areas. It is never found along the coast. (5) Yet another parasite, Prospaltella perniciosi Tower, has its range restricted by competition and not by weather although it gives the appearance of being restricted by weather because it occurs only in coastal districts. (6) Examples are discussed of interactions between weather and dust, ants, or chemicals with parasites and hosts which result in various modifications of the abundance of the host and parasites. (7) Examples are discussed of the effect of weather on interactions between competing species of parasites and the host which have resulted in striking modifications of the previous distribution of certain parasites.

The cercarial output from three Nigerian bulinids infected with two strains of Schistosoma haematobium

1988 ◽  
Vol 62 (2) ◽  
pp. 133-140 ◽  
Author(s):  
S. E. Fryer ◽  
A. J. Probert
Keyword(s):  
Schistosoma Haematobium ◽  
Daily Production ◽  
Bulinus Truncatus ◽  
Low Levels ◽  
Host Parasite ◽  
Second Period ◽  
Initial Peak

ABSTRACTThe daily cercarial output of two Nigerian strains of Schistosoma haematobium in sympatric Bulinus truncatus, B. globosus and B. senegalensis was measured at weekly intervals from the start of emission to the snails' death. In all cases cercariae were released throughout the life of the host, with no cases of “self cure”. Patterns of output through the course of infections in B. truncatus and B. senegalensis were similar to those reported for S. haematobium by other workers, with daily production of cercariae rising to a peak within a few weeks of the onset of shedding, then declining until the host's death. In the longer lived B. globosus production was significantly higher, but declined to very low levels after the initial peak; in some individuals cercarial output remained very low, while others showed a second period of high cercarial emission. The relative compatibility of each host-parasite combination is discussed.

The effect of the acanthocephalan Pomphorhynchus laevis upon the respiration of its intermediate host, Gammarus pulex

Parasitology ◽  
1974 ◽  
Vol 68 (2) ◽  
pp. 271-284 ◽  
Author(s):  
A. E. Rumpus ◽  
C. R. Kennedy
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Host Population ◽  
Gammarus Pulex ◽  
Multiple Infections ◽  
Pomphorhynchus Laevis ◽  
Respiration Rates ◽  
Physiological Processes ◽  
Stage Of Development ◽  
Host Parasite

The respiration rates of individual Gammarus pulex infected by larval Pomphorhynchus laevis were investigated with particular reference to the stage of development of the host and parasite and to the water temperature. At 20°C the oxygen consumption of Gammarus of all sizes was reduced by an average of 19·3 % by the presence of cystacanths of the parasite, but was unaffected by the presence of acanthellae. It is considered that the small size of this larval stage, in relation to that of its host, is responsible for the failure to detect an effect. Multiple infections did not exert any greater effect upon host respiration than single cystacanths, nor did it appear that the parasite had different effects upon hosts of different sexes. At 10°C no significant differences were observed between the respiration rates of infected and uninfected gammarids. The parasite was probably still depressing the host respiration rate at this temperature, but the oxygen uptake of G. pulex is so low that the differences between infected and uninfected individuals were too small to be detected. The parasite has a direct effect upon the physiological processes of the host, but neither the mechanism of this nor the reasons for the different effects found in different host-parasite systems are yet understood. Despite the pronounced effect of P. laevis on respiration of individual hosts, its effect upon the oxygen consumption of a natural host population is small since only a small proportion of the population carries infections and water temperatures remain below 10°C for over half the year.

Population variation in the metabolic response of deer mice to infection with Capillaria hepatica (Nematoda)

2001 ◽  
Vol 79 (4) ◽  
pp. 554-561 ◽  
Author(s):  
Shawn Meagher ◽  
Timothy P O'Connor
Keyword(s):  
Cold Stress ◽  
Metabolic Response ◽  
Host Population ◽  
Population Variation ◽  
Deer Mice ◽  
Negative Consequences ◽  
Capillaria Hepatica ◽  
Generation Times ◽  
Stress Maximum ◽  
Host Parasite

The effects of parasites on their hosts can vary among host populations, but few studies have examined geographic variation in host-parasite interactions. We examined the effects of Capillaria hepatica (Nematoda) infection on deer mice (Peromyscus maniculatus gracilis) from two different populations. Specifically, we measured the basal metabolic rate (BMR), cold-stress maximum oxygen consumption (MRpeak), metabolic scope (MRpeak/BMR), and thermogenic endurance of infected and uninfected mice from one population with, and a second population without, a history with C. hepatica. Infection had no effect on BMR, but did have effects on cold-stress measures. A previous study documented a significant relationship between survival and MRpeak in wild deer mice; hence, the effects of infection on the parameters that we measured could influence fitness. Only mice that had no historical association with C. hepatica displayed negative consequences of infection, which suggests that the historical host population has evolved mechanisms to cope with infection. Models of the evolution of virulence should include evolutionary responses of both hosts and parasites, particularly when systems involve macroparasites that have long generation times.

scholarly journals Assessing the direct and indirect effects of food provisioning and nutrient enrichment on wildlife infectious disease dynamics

2018 ◽  
Vol 373 (1745) ◽  
pp. 20170101 ◽  
Author(s):  
David J. Civitello ◽  
Brent E. Allman ◽  
Connor Morozumi ◽  
Jason R. Rohr
Keyword(s):  
Nutrient Enrichment ◽  
Management Strategies ◽  
Wildlife Disease ◽  
Host Population ◽  
Food Provisioning ◽  
Resource Subsidies ◽  
Predator Species ◽  
Interacting Species ◽  
Integrative View ◽  
Host Parasite

Anthropogenic resource supplementation can shape wildlife disease directly by altering the traits and densities of hosts and parasites or indirectly by stimulating prey, competitor or predator species. We first assess the direct epidemiological consequences of supplementation, highlighting the similarities and differences between food provisioning and two widespread forms of nutrient input: agricultural fertilization and aquatic nutrient enrichment. We then review an aquatic disease system and a general model to assess whether predator and competitor species can enhance or overturn the direct effects of enrichment. All forms of supplementation can directly affect epidemics by increasing host population size or altering parasite production within hosts, but food provisioning is most likely to aggregate hosts and increase parasite transmission. However, if predators or competitors increase in response to supplementation, they could alter resource-fuelled outbreaks in focal hosts. We recommend identifying the traits of hosts, parasites or interacting species that best predict epidemiological responses to supplementation and evaluating the relative importance of these direct and indirect mechanisms. Theory and experiments should examine the timing of behavioural, physiological and demographic changes for realistic, variable scenarios of supplementation. A more integrative view of resource supplementation and wildlife disease could yield broadly applicable disease management strategies. This article is part of the theme issue ‘Anthropogenic resource subsidies and host–parasite dynamics in wildlife’.

Influence of Winter Annual Weed Removal Timings on Soybean Cyst Nematode Population Density and Plant Biomass

Weed Science ◽  
2010 ◽  
Vol 58 (4) ◽  
pp. 381-386 ◽  
Author(s):  
Valerie A. Mock ◽  
J. Earl Creech ◽  
Virginia R. Ferris ◽  
Steven G. Hallett ◽  
William G. Johnson
Keyword(s):  
Soybean Cyst Nematode ◽  
Plant Biomass ◽  
Cyst Nematode ◽  
Population Increase ◽  
Population Densities ◽  
Soybean Production ◽  
Winter Annual ◽  
Winter Annual Weeds ◽  
Annual Weeds ◽  
Weed Removal

Soybean cyst nematode (SCN) is one of the most yield limiting pathogens in U.S. soybean production. Henbit and purple deadnettle are winter annual weeds shown to facilitate SCN reproduction after crop harvest in the eastern Corn Belt. These weeds, along with volunteer soybean that germinates in autumn after harvest, are common to postharvest soybean production fields and provide an opportunity for SCN reproduction and population increase outside of the typical soybean production season. The objective of this experiment was to determine if autumn removal of these weeds and volunteer soybean can influence the winter weed seedbank, plant biomass, and SCN population densities. Microplots were established with or without Lamium spp. and volunteer soybean, and four winter weed removal timings (none, October, December, and May). Dry weights of autumn Lamium spp. were reduced 50% in October when grown in competition with volunteer soybean. SCN juveniles were found in henbit roots at higher densities in October (42 per gram of root) than December (5 per gram of root) and were also found in the roots of volunteer soybean (14 per gram of root) in October. SCN egg population densities were 50% lower in August after the summer fallow period. The results of this experiment suggest that autumn removal of winter annual weeds and volunteer soybean did not reduce SCN populations.

scholarly journals The mode of host–parasite interaction shapes coevolutionary dynamics and the fate of host cooperation

2012 ◽  
Vol 279 (1743) ◽  
pp. 3742-3748 ◽  
Author(s):  
Benjamin J. Z. Quigley ◽  
Diana García López ◽  
Angus Buckling ◽  
Alan J. McKane ◽  
Sam P. Brown
Keyword(s):  
Stochastic Modelling ◽  
Host Population ◽  
Social Traits ◽  
The Social ◽  
Population Structures ◽  
Modelling Techniques ◽  
Virus Interactions ◽  
Host Parasite ◽  
The Impact ◽  
Genetic Specificity

Antagonistic coevolution between hosts and parasites can have a major impact on host population structures, and hence on the evolution of social traits. Using stochastic modelling techniques in the context of bacteria–virus interactions, we investigate the impact of coevolution across a continuum of host–parasite genetic specificity (specifically, where genotypes have the same infectivity/resistance ranges (matching alleles, MA) to highly variable ranges (gene-for-gene, GFG)) on population genetic structure, and on the social behaviour of the host. We find that host cooperation is more likely to be maintained towards the MA end of the continuum, as the more frequent bottlenecks associated with an MA-like interaction can prevent defector invasion, and can even allow migrant cooperators to invade populations of defectors.

Population regulation in ticks: the role of acquired resistance in natural and unnatural hosts

Parasitology ◽  
1979 ◽  
Vol 79 (1) ◽  
pp. 141-156 ◽  
Author(s):  
Sarah E. Randolph
Keyword(s):  
Population Regulation ◽  
Acquired Resistance ◽  
Subsequent Development ◽  
Immunological Response ◽  
Threshold Level ◽  
Tick Population ◽  
Dependent Manner ◽  
Laboratory Mice ◽  
Natural Hosts ◽  
Host Parasite

SUMMARYAttachment, engorgement and subsequent development of successive infestations of Ixodes trianguliceps larvae and nymphs on natural hosts, Apodemus sylvaticus, and unnatural hosts, laboratory mice, are compared. In laboratory mice, primary infestations above a threshold level of about 10 ticks elicit an immunological response which reduces, in a density-dependent manner, the rate of successful tick engorgement during subsequent infestations. In contrast, in A. sylvaticus successive infestations of larvae result in unchanged or slightly improved survival through to nymphs. The relevance of these results to the concept of host-parasite co-evolution and to tick population regulation is discussed.

SEASONAL ABUNDANCE OF RED AND GREEN MORPHS OF THE TOBACCO APHID (HOMOPTERA: APHIDIDAE) ON FLUE-CURED TOBACCO IN GEORGIA

1989 ◽  
Vol 24 (4) ◽  
pp. 531-538 ◽  
Author(s):  
Robert M. McPherson
Keyword(s):  
High Temperatures ◽  
Field Experiments ◽  
Aphid Population ◽  
Seasonal Abundance ◽  
Population Increase ◽  
Population Densities ◽  
Early Season ◽  
Myzus Nicotianae ◽  
Aphid Populations ◽  
Tobacco Aphid

The seasonal abundance of red and green morphs of the tobacco aphid, Myzus nicotianae Blackman, was investigated on flue-cured tobacco in Georgia during 1987–1988. The effect of tobacco transplantation date also was examined in 1988. Aphid populations peaked on tobacco in mid-June 1987, then rapidly declined following the removal of the terminal floral branch (topping). Early season samples contained both green and red morphs; however, by early June, and throughout the remainder of the season, the aphid population was almost exclusively comprised of the red morph. Similar results were obtained in 1988, although population densities were higher and peaked earlier in the early transplanting (30 March) compared to the 14 April and 28 April transplantings. Regardless of transplanting date, the red morphs began a rapid population increase about 45 days after transplantation, and this increase continued until plants were topped. Daily high temperatures exceeding 35°C did not appear detrimental to the red morphs in these field experiments.

The regulation of host population growth by parasitic species

Parasitology ◽  
1978 ◽  
Vol 76 (2) ◽  
pp. 119-157 ◽  
Author(s):  
R. M. Anderson
Keyword(s):  
Population Growth ◽  
Reproductive Potential ◽  
Parasite Burden ◽  
Host Population ◽  
Parasitic Species ◽  
Regulatory Influence ◽  
Host Mortality ◽  
Parasite Reproduction ◽  
Over Dispersion ◽  
Host Parasite

SummaryThe nature of parasitism at the population level is defined in terms of the parasite's influence on the natural intrinsic growth rate of its host population. It is suggested that the influence on this rate is related to the average parasite burden/host and hence to the statistical distribution of parasites within the host population.Theoretical models of host–parasite associations are used to assess the regulatory influence of parasitic species on host population growth. Model predictions suggest that three specific groups of population processes are of particular importance: over-dispersion of parasite numbers/host, density dependence in parasite mortality or reproduction and parasite-induced host mortality that increases faster than linearly with the parasite burden. Other population mechanisms are shown to have a destabilizing influence, namely: parasite-induced reduction in host reproductive potential, direct parasite reproduction within the host and time delays in the development of transmission stages of the parasite.These regulatory and destabilizing processes are shown to be commonly observed features of natural host-parasite associations. It is argued that interactions in the real world are characterized by a degree of tension between these regulatory and destabilizing forces and that population rate parameter values in parasite life-cycles are very far from being a haphazard selection of all numerically possible values. It is suggested that evolutionary pressures in observed associations will tend to counteract a strong destabilizing force by an equally strong regulatory influence. Empirical evidence is shown to support this suggestion in, for example, associations between larval digeneans and molluscan hosts (parasite-induced reduction in host reproductive potential counteracted by tight density-dependent constraints on parasite population growth), and interactions between protozoan parasites and mammalian hosts (direct parasite reproduction counteracted by a well-developed immunological response by the host).The type of laboratory and field data required to improve our understanding of the dynamical properties of host–parasite population associations is discussed and it is suggested that quantitative measurement of rates of parasite-induced host mortality, degrees of over-dispersion, transmission rates and reproductive and mortality rates of both host and parasite would provide an important first step. The value of laboratory work in this area is demonstrated by reference to studies which highlight the regulatory influence of parasitic species on host population growth.

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