Parasites alter host phenotype and may create a new ecological niche for snail hosts - PubMed (original) (raw)

Parasites alter host phenotype and may create a new ecological niche for snail hosts

Osamu Miura et al. Proc Biol Sci. 2006.

Abstract

By modifying the behaviour and morphology of hosts, parasites may strongly impact host individuals, populations and communities. We examined the effects of a common trematode parasite on its snail host, Batillaria cumingi (Batillariidae). This widespread snail is usually the most abundant invertebrate in salt marshes and mudflats of the northeastern coast of Asia. More than half (52.6%, n=1360) of the snails in our study were infected. We found that snails living in the lower intertidal zone were markedly larger and exhibited different shell morphology than those in the upper intertidal zone. The large morphotypes in the lower tidal zone were all infected by the trematode, Cercaria batillariae (Heterophyidae). We used a transplant experiment, a mark-and-recapture experiment and stable carbon isotope ratios to reveal that snails infected by the trematode move to the lower intertidal zone, resume growth after maturation and consume different resources. By simultaneously changing the morphology and behaviour of individual hosts, this parasite alters the demographics and potentially modifies resource use of the snail population. Since trematodes are common and often abundant in marine and freshwater habitats throughout the world, their effects potentially alter food webs in many systems.

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Figures

Figure 1

Figure 1

Body size and habitat differentiation between uninfected and infected snails in OT. (a) Mean shell length along the vertical gradients. (b) Prevalence of C. batillariae and other trematode species along the vertical gradients. Error bars represent±1 s.e.

Figure 2

Figure 2

Mean shell length of uninfected and infected snails along the vertical gradients in all three sites (a) OT (b) MK (c) IK. Error bars represent±1 s.e. Samples of fewer than 5 individuals are not shown.

Figure 3

Figure 3

The growth rate of uninfected and infected snails. (a) Relationship between growth rate and shell width in uninfected B. cumingi snails and in those infected by the trematode, C. batillariae. The data are shown as logarithmic dot-plots. The regression lines were calculated with linear regression on raw data for infected and uninfected snails. (b) Examples of marked shells of uninfected (left) and infected (right) snails (scale bar, 1 cm). The snail on the left shows the thickened lip of the aperture (varix) indicating cessation of rapid growth in an uninfected snail. The snail on the right, infected by C. batillariae, exhibits gigantism, rapid growth beyond the varix. The arrow indicates the varix (old maturation point) of the infected snail.

Figure 4

Figure 4

Locations of recaptured snails. Open circles indicate uninfected snails, and filled circles indicate snails infected by C. batillariae. The area of each circle is proportional to the number of the snails found at each location. The intersection of dotted lines indicates the release location of marked snails.

References

    1. Baudoin M. Host castration as a parasitic strategy. Evolution. 1975;29:335–352. -PubMed
    1. Berdoy M, Webster J.P, Macdonald D.W. Fatal attraction in rats infected with Toxoplasma gondii. Proc. R. Soc. B. 2000;267:1591–1594. -DOI -PMC -PubMed
    1. Byers J.E. Competition between two estuarine snails: implications for invasions of exotic species. Ecology. 2000;81:1225–1239.
    1. Combes C. Ethological aspects of parasite transmission. Am. Nat. 1991;138:867–880. -DOI
    1. Curtis L.A. Vertical distribution of an estuarine snail altered by a parasite. Science. 1987;235:1509–1511. -PubMed

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