Host choice by larval parasites: a study of Biomphalaria glabrata snails and Schistosoma mansoni miracidia related to host size

Abstract

Within snail/trematode associations the age/size of the host at infection has consequences with regard to miracidial infection success, further intramolluscan parasite development and reproduction, and the host response, mainly in terms of growth and reproductive effort. Taking into account these differences, we were interested in determining whether miracidia could discriminate and make a choice between snails of different sizes. Using the Schistosoma mansoni/Biomphalaria glabrata system, we compared data on the snail infection rate and the mother sporocyst abundance among three size classes of snails (juvenile, subadult, and adult) exposed separately or together to the parasite larvae. When exposed individually, juvenile snails (3-5 mm) had significantly higher prevalence and abundance values than did subadult snails, followed by adult snails. In contrast, when snails of the three size classes were exposed together in heterogeneous size groups the prevalence and abundance values were always significantly higher for subadult snails of the 7- to 9-mm class than for juvenile and adult snails. A host choice experiment confirmed that significantly more miracidia were attracted by subadult snails, suggesting that the parasite has been selected for specific locating and recognition mechanisms increasing the infection rate of subadult snails when the latter have been exposed in a heterogeneous size group. Selective forces that may be responsible for such a preferential infectivity of the parasite vis-à-vis particular host age/size class are discussed in relation to host resources and host responses.

High temperature enhances host pathology in a snail–trematode system: possible consequences of climate change for the emergence of disease

“…These results indicate that earlier spring warming owing to climate change may disproportionately increase the hatching rate of R. ondatrae eggs relative to snail development, such that snails may be infected at a smaller size. This could alter the dynamics of R. ondatrae , since many aspects of trematode infections in snails are influenced by the size of the snail at infection, including both infection success and snail mortality (Kuris, 1980; Theron, Rognon & Pages, 1998).…”

Resources, key traits and the size of fungal epidemics in Daphnia populations

“…Similarly, improved condition could promote host growth. Larger hosts can have higher infection risk since they provide larger targets for vectors or free‐living parasites (Théron, Rognon & Pagés ; Daost et al . ).…”

“…Similarly, improved condition could promote host growth. Larger hosts can have higher infection risk since they provide larger targets for vectors or freeliving parasites (Th eron, Rognon & Pag es 1998;Daost et al 2010). Additionally, larger hosts may encounter more trophically transmitted parasites because they feed faster than smaller conspecifics (Hall et al 2007).…”

Drivers of aggregation in a novel arboreal parasite: the influence of host size and infra-populations

“…Host quality determines parasite growth, reproductive success, and survival (Théron et al, 1998;Barber, 2005;Tschirren et al, 2007;Poulin and Forbes, 2011). Parasites aggregate, whereby few parasites infect many hosts and many parasites infect few hosts (Shaw et al, 1998;Tschirren et al, 2007;Calabrese et al, 2011;Poulin and Forbes, 2011;Poulin, 2013).…”

“…Furthermore, parasite dissemination and infection mode influence host selection (Lester, 2012;Poulin, 2013). Overall parasite success relies on discriminating between heterogeneous hosts in fragmented populations (Théron et al, 1998). Host selection is particularly significant for New Zealand's largest endemic moth, Aenetus virescens (Doubleday) (Lepidoptera: Hepialidae), which has arguably the most unique lepidopteran life history on earth.…”