Parasite abundance decreases with host density: evidence of the encounter-dilution effect for a parasite with a complex life cycle

Buck, Julia C.; Lutterschmidt, William I.

doi:10.1007/s10750-016-2874-8

Cited by 43 publications

(43 citation statements)

References 30 publications

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“…, Rohr et al. ) and natural populations (Ewers , Buck and Lutterschmidt ) that showed reduced per capita infection risk for hosts living at high densities. Our results appear to contrast with findings that microphallid trematode abundance in a second intermediate isopod host was higher at sites with higher isopod density (Hansen and Poulin ).…”

Section: Discussionmentioning

confidence: 99%

“…) and natural populations (Ewers ), and trematode metacercaria abundance in second intermediate hosts declines with increasing host density in mesocosms (Rohr et al. ) and natural populations (Buck and Lutterschmidt ). Although elevated host density in a patch is predicted to reduce per capita infection risk (Anderson ), evidence for safety in numbers due to infective‐stage depletion from a field study that tracks parasite recruitment has been lacking, and no study has scaled up from the patch to the entire host population.…”

Section: Introductionmentioning

confidence: 99%

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Host density increases parasite recruitment but decreases host risk in a snail–trematode system

Buck

Hechinger

Wood

et al. 2017

Ecology

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Most species aggregate in local patches. High host density in patches increases contact rate between hosts and parasites, increasing parasite transmission success. At the same time, for environmentally transmitted parasites, high host density can decrease infection risk to individual hosts, because infective stages are divided among all hosts in a patch, leading to safety in numbers. We tested these predictions using the California horn snail, Cerithideopsis californica (=Cerithidea californica), which is the first intermediate host for at least 19 digenean trematode species in California estuaries. Snails become infected by ingesting trematode eggs or through penetration by free-swimming miracidia that hatch from trematode eggs deposited with final-host (bird or mammal) feces. This complex life cycle decouples infective-stage production from transmission, raising the possibility of an inverse relationship between host density and infection risk at local scales. In a field survey, higher snail density was associated with increased trematode (infected snail) density, but decreased trematode prevalence, consistent with either safety in numbers, parasitic castration, or both. To determine the extent to which safety in numbers drove the negative snail-density-trematode-prevalence association, we manipulated uninfected snail density in 83 cages at eight sites within Carpinteria Salt Marsh (California, USA). At each site, we quantified snail density and used data on final-host (bird and raccoon) distributions to control for between-site variation in infective-stage supply. After three months, overall trematode infections per cage increased with snail biomass density. For egg-transmitted trematodes, per-snail infection risk decreased with snail biomass density in the cage and surrounding area, whereas per-snail infection risk did not decrease for miracidium-transmitted trematodes. Furthermore, both trematode recruitment and infection risk increased with infective-stage input, but this was significant only for miracidium-transmitted species. A model parameterized with our experimental results and snail densities from 524 field transects estimated that safety in numbers, when combined with patchy host density, halved per capita infection risk in this snail population. We conclude that, depending on transmission mode, host density can enhance parasite recruitment and reduce per capita infection risk.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Host density increases parasite recruitment but decreases host risk in a snail–trematode system

Buck

Hechinger

Wood

et al. 2017

Ecology

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“…The use of parasites as a bioindicator of ecosystem health is not novel [63,64] and may be particularly useful in environmental monitoring [65][66][67] and the monitoring of anthropogenic related pollutants [68]. Buck and Lutterschmidt further illustrated the link between host density, which is influenced by urbanization, and parasite abundance within this aquatic system [30].…”

Section: Discussionmentioning

confidence: 99%

“…A Previous survey of fishes (Permit # 29-WMB-01-147) was conducted in June 2001 and August 2002 [28] and served as the foundational data for investigating the effects of urbanization on biodiversity [28][29][30]. In October 2012, we collected only Lepomis specimens (Permit # 29-WJH-12-192) for this study using a backpack electrofisher until a minimum of 20 L. auritus and/or L. macrochirus were obtained from each of the eight creeks.…”

Section: Fish Collectionmentioning

confidence: 99%

“…This watershed ( Figure 1) is experiencing rapid urban development and changes in land-use which are predicted to influence common metrics of environmental quality. This study and other related investigations (e.g., [28][29][30]) were aimed at assessing potential biological and environmental effects of land-use change related to urbanization. Biodiversity metrics, indicator species and FA could serve as potential ecological drivers in the application of the Land use Evolution and impact Assessment Model (LEAM) at Fort Benning.…”

Section: Introductionmentioning

confidence: 99%

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Fluctuating Asymmetry in Two Common Freshwater Fishes as a Biological Indicator of Urbanization and Environmental Stress within the Middle Chattahoochee Watershed

2016

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Deviations in bilateral symmetry or fluctuating asymmetry of an organism may result under environmental stressors that reduce developmental homeostasis and stability. Anthropogenic stressors such as increased urbanization can negatively impact environmental quality of aquatic ecosystems. Researchers have stressed the value in finding easy, accurate and inexpensive methods for assessing potential stress within ecosystems. Here we use fluctuating asymmetry (FA) as a useful quantitative tool in assessing the environmental quality and potential urban-based stressors within eight creeks of the Bull and Upatoi Creeks Watershed within the larger watershed of the Middle Chattahoochee. Using Geographic Information System (GIS), we characterize land-use patterns and a decreasing urbanization gradient as related to each creek's eastward position from Columbus, Georgia. We collected two common fishes (redbreast sunfish; Lepomis auritus and bluegill; Lepomis macrochirus), measured both metric and meristic traits and investigated if the degree of FA in these two common fishes correlated with the urbanization gradient across creeks. We found significant differences in FA among creeks with one of the highest FA measures for the most urban creek. Principal component analysis (PCA) scores of urbanization and water chemistry were regressed against FA scores. We found no significant relationship between urbanization and FA nor environmental water chemistry and FA among creeks. We comment on the use of FA as a potential response variable and biological indicator of environmental stress within this watershed.

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Crowding does not affect monarch butterflies’ resistance to a protozoan parasite

Alaidrous

Villa

Roode

et al. 2022

Ecology and Evolution

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Host density is an important factor when it comes to parasite transmission and host resistance. Increased host density can increase contact rate between individuals and thus parasite transmission. Host density can also cause physiological changes in the host, which can affect host resistance. Yet, the direction in which host density affects host resistance remains unresolved. It is also unclear whether food limitation plays a role in this effect. We investigated the effect of larval density in monarch butterflies, Danaus plexippus , on the resistance to their natural protozoan parasite Ophryocystis elektroscirrha under both unlimited and limited food conditions. We exposed monarchs to various density treatments as larvae to mimic high densities observed in sedentary populations. Data on infection and parasite spore load were collected as well as development time, survival, wing size, and melanization. Disease susceptibility under either food condition or across density treatments was similar. However, we found high larval density impacted development time, adult survival, and wing morphology when food was limited. This study aids our understanding of the dynamics of environmental parasite transmission in monarch populations, which can help explain the increased prevalence of parasites in sedentary monarch populations compared to migratory populations.

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Parasite abundance decreases with host density: evidence of the encounter-dilution effect for a parasite with a complex life cycle

Cited by 43 publications

References 30 publications

Host density increases parasite recruitment but decreases host risk in a snail–trematode system

Host density increases parasite recruitment but decreases host risk in a snail–trematode system

Fluctuating Asymmetry in Two Common Freshwater Fishes as a Biological Indicator of Urbanization and Environmental Stress within the Middle Chattahoochee Watershed

Crowding does not affect monarch butterflies’ resistance to a protozoan parasite

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