Explaining variability in parasite aggregation levels among host samples

SUMMARYAggregated distributions among individual hosts are a defining feature of metazoan parasite populations. Heterogeneity among host individuals in exposure to parasites or in susceptibility to infection is thought to be the main factor generating aggregation, with properties of parasites themselves explaining some of the variability in aggregation levels observed among species. Here, using data from 410 samples of helminth parasites on fish hosts, I tested the contribution of (i) within-sample variation in host body size, taken as a proxy for variability in host susceptibility, and (ii) parasite taxon and developmental stage, to the aggregated distribution of parasites. Log-transformed variance in numbers of parasites per host was regressed against log mean number across all samples; the strong relationship (r2 = 0·88) indicated that aggregation levels are tightly constrained by mean infection levels, and that only a small proportion of the observed variability in parasite aggregation levels remains to be accounted for by other factors. Using the residuals of this regression as measures of ‘unexplained’ aggregation, a mixed effects model revealed no significant effect of within-sample variation in host body size or of parasite taxon or stage (i.e. juvenile versus adult) on parasite aggregation level within a sample. However, much of the remaining variability in parasite aggregation levels among samples was accounted for by the number of individual hosts examined per sample, and species-specific and study-specific effects reflecting idiosyncrasies of particular systems. This suggests that with most differences in aggregation among samples already explained, there may be little point in seeking universal causes for the remaining variation.

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Consumer and host body size effects on the removal of trematode cercariae by ambient communities

Parasitology ◽

10.1017/s0031182018001488 ◽

2018 ◽

Vol 146 (3) ◽

pp. 342-347

Author(s):

Jennifer E. Welsh ◽

Anke Hempel ◽

Mirjana Markovic ◽

Jaap van der Meer ◽

David W. Thieltges

Keyword(s):

Body Size ◽

Size Effects ◽

Laboratory Experiments ◽

Feeding Activity ◽

Removal Rates ◽

Host Interactions ◽

Host Body ◽

Species Specific ◽

Host Body Size ◽

Significant Mortality

AbstractParasite transmission can be altered via the removal of parasites by the ambient communities in which parasite–host interactions take place. However, the mechanisms driving parasite removal remain poorly understood. Using marine trematode cercariae as a model system, we investigated the effects of consumer and host body size on parasite removal rates. Laboratory experiments revealed that consumer or host body size significantly affected cercarial removal rates in crabs, oysters and cockles but not in shrimps. In general, cercarial removal rates increased with consumer (crabs and oysters) and host (cockles) body size. For the filter feeding oysters and cockles, the effects probably relate to their feeding activity which is known to correlate with bivalve size. Low infection levels found in cockle hosts suggest that parasite removal by hosts also leads to significant mortality of infective stages. The size effects of crab and shrimp predators on cercarial removal rates were more complex and did not show an expected size match-mismatch between predators and their cercarial prey, suggesting that parasite removal rates in predators are species-specific. We conclude that to have a comprehensive understanding of parasite removal by ambient communities, more research into the various mechanisms of cercarial removal is required.

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The evolution of body size in the Monogenea: the role of host size and latitude

Canadian Journal of Zoology ◽

10.1139/z96-082 ◽

1996 ◽

Vol 74 (4) ◽

pp. 726-732 ◽

Cited By ~ 17

Author(s):

Robert Poulin

Keyword(s):

Body Size ◽

Interspecific Variation ◽

Host Size ◽

Independent Contrasts ◽

Related Factors ◽

Host Body ◽

Phylogenetically Independent Contrasts ◽

Using Data ◽

Host Body Size

Monogeneans form a diverse group of parasitic platyhelminths that show substantial interspecific variation in body size, though this variation remains largely unexplained. The relationships between monogenean body size and both host body size and latitude were examined in comparative analyses using data from 613 monogenean species. First, phylogenetically independent contrasts among 39 monogenean families revealed no relationship between host size and parasite size. However, large parasite size was consistently associated with high latitude, suggesting that larger body size in monogeneans may result more from external factors such as temperature than from host-related factors. The potential effects of other variables (site of attachment on the host, host taxonomy, and type of aquatic habitat) could not be assessed in the analysis. Second, analyses among genera within families failed to show any consistent relationships between monogenean body size and either host size or latitude. The results of this study suggest that latitude had an evolutionary influence on monogenean body size, though this may be only visible in comparisons among higher taxonomic levels, and that monogenean body size has not simply adjusted to host body size following host-switching events.

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First study on the helminth community structure of the neotropical marsupial Metachirus myosuros (Didelphimorphia, Didelphidae)

Revista Brasileira de Parasitologia Veterinária ◽

10.1590/s1984-29612020064 ◽

2020 ◽

Vol 29 (3) ◽

Author(s):

Bruna Silva Cirino ◽

Sócrates Fraga da Costa Neto ◽

Arnaldo Maldonado Júnior ◽

Rosana Gentile

Keyword(s):

Community Structure ◽

Body Size ◽

Abundant Species ◽

Northeastern Brazil ◽

Helminth Parasites ◽

Helminth Community ◽

Component Community ◽

Host Body ◽

Marsupial Species ◽

Host Body Size

Abstract Metachirus myosuros is a marsupial species widely distributed in South America. Despite this, there is a lack of knowledge about its helminth parasites and helminth community structure. The aims of this study were to describe the species composition and determine the parasitological parameters of helminth communities of M. myosuros in preserved areas of the Atlantic Forest, Igrapiúna, Bahia state, northeastern Brazil. Parasites were searched from 19 specimens of this marsupial (18 were infected with at least one species), counted and identified. Ten species of helminth parasites were obtained: 7 nematodes, 2 platyhelminths and 1 acanthocephalan. The most abundant species were Aspidodera raillieti, Cruzia tentaculata, Physaloptera mirandai and Viannaia conspicua (Nematoda). These species were also the only dominant ones in the component community. Male hosts had higher prevalence of P. mirandai and greater abundance of V. conspicua. We observed a relationship between host body size and helminth abundance in both male and female hosts, and between host body size and helminth species richness in female hosts. This was the first study to analyze the helminth fauna and helminth community structure of M. myosuros. This was the first report of occurrences of A. raillieti and Didelphonema longispiculata in M. myosuros.

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Helminth communities in the burrowing toad, Rhinella fernandezae, from Northeastern Argentina

Biologia ◽

10.2478/s11756-013-0272-5 ◽

2013 ◽

Vol 68 (6) ◽

Cited By ~ 6

Author(s):

Monika Hamann ◽

Arturo Kehr ◽

Cynthya González

Keyword(s):

Species Richness ◽

Body Size ◽

Feeding Habits ◽

Abiotic Factors ◽

Helminth Species ◽

Individual Species ◽

Helminth Parasites ◽

Importance Value ◽

Host Body ◽

Host Body Size

AbstractThe main goals of this study were to determine the richness and diversity of helminth parasites of Rhinella fernandezae at the component and infracommunity levels and determine the ecological implications of different biotic and abiotic factors. Specimens were collected near the city of Corrientes, Corrientes Province, Argentina. Prevalence of infection was 94% in the specimens examined (n = 65). The helminth component community in R. fernandezae in this area was comprised a total of 22 species. Of all helminth species, only three (Catadiscus inopinatus, Cosmocerca podicipinus and C. parva) were dominant (importance value: I > 1.0) in the community. The most abundant species were B. tetracotyloides (d = 0.43) among the larvae and C. podicipinus (d = 0.09) among adult worms. At the infracommunity level, the mean individual species richness (2.28 ± 1.48) (mean ± SD) was no more than 3 helminth species per infected host; the diversity and equitability of helminths were 0.23 ± 0.21 and 0.48 ± 0.38, respectively. The host body size was the main factor in determining the parasite abundance. Species richness was significantly and positively correlated with host body size. The parasite helminth species predominantly showed an overdispersed pattern of distribution. Helminth species showed two negative and significant pairs of covariation and one significant pair of association (P < 0.05). R. fernandezae has a wide variety of parasites relating to the host microhabitat, mobility and feeding habits.

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