Journal Molluscan Studies Advance Access originally published online on June 16, 2009
Journal of Molluscan Studies 2009 75(4):391-396; doi:10.1093/mollus/eyp035
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Correlation between parasite prevalence and adult size in a trematode-mollusc system: evidence for evolutionary gigantism in the freshwater snail Galba truncatula?
1Department of Ecology and Evolution, Biophore, University of Lausanne, CH-1015 Lausanne, Switzerland; and 2Present address: Institut des Sciences de l'Évolution UMR 5554, Place Eugène Bataillon, CC 65–Université Montpellier 2, 34095 Montpellier cedex 5, France
Correspondence: E. Chapuis; e-mail: elodie.chapuis{at}univ-montp2.fr
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Abstract |
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The snail-trematode host-parasite system has been widely studied, as trematodes are known to greatly influence the fitness of their hosts. Indeed, during their development, the trematodes castrate the snail and one possible consequence of infection is gigantism of the snail. Snail gigantism is usually investigated experimentally by comparing the size of healthy and artificially infected snails. Here, I focused on naturally infected populations in order to investigate if snails submitted to trematode pressure have evolved specific life-history traits to respond to the parasite prevalence in their natural population. To this end, I estimated the correlations between measures of size (obtained from healthy laboratory individuals originating from populations) and the parasite prevalence at the population level. I found that the adult size of populations was positively correlated with population prevalence, an indication that gigantism might be operating. Moreover, I found a positive relation between growth and fecundity in healthy populations, while no such trade off was found in highly parasitized populations, suggesting that there may be a cost in fecundity to this gigantism.
(Received 14 January 2009; accepted 5 May 2009)