Thermal preferences of resistant and susceptible strains ofBiomphalaria glabrata(Gastropoda) exposed toschistosoma mansoni(Trematoda)

Abstract

The thermal preferences of two strains of the snail Biomphalaria glabrata, one resistant to, and one susceptible to, the parasite Schistosoma mansoni were determined in an aquatic thermal gradient. Snails were tested without exposure to the parasite, and 2 h and 5 weeks after exposure to trematode miracidia. The mean temperature selected by susceptible strain snails 2 h post-exposure tended to be lower than that of unexposed controls, although this was not statistically significant. In this strain, at 5 weeks post-exposure, the preferred temperature dropped by 1.9 +/- 0.5 degree C. The resistant strain displayed a significant drop of 1.8 +/- 0.6 degree C 2 h post-exposure. These results are consistent with the hypothesis that a drop in mean temperatures selected by snails is due to altered levels of endogenous cytokines such as IL-1 or TNF in association with parasite activation of the snail internal defense system.

Symptoms of behavioural anapyrexia – Reverse fever as a defence response of snails to fluke invasion

“…This treatment imitated mechanical damage to the body caused by the passage of cercariae through the epithelium of the host. Snails penetrated by miracidia also responded with a reduction in the preferred temperature (Lefcort and Bayne, 1991), as did individuals shedding cercariae of several species of these parasites ( _ Zbikowska, 2006). According to these authors, an invasion of miracidia and shedding cercariae constitute two critical moments in the snail-trematode interaction, during which, for example, the number of active hemocytes in the host hemolymph increases significantly.…”

Parasitized snails take the heat: a case of host manipulation?

“…Instead, snails infected with Philophthalmus display characteristics which are typical of general infection-related responses to elevated heat, including decreased activity, that in other infected invertebrates relate to physiological alterations upon infection that may or may not be advantageous to either the host or parasite (Holmes and Zohar 1990;Ewald 1980). For instance, Lefcort and Bayne (1991) reported that the drop in the mean temperatures selected by one snail species (Biomphalaria glabrata) infected by a trematode (Schistosoma mansoni) may relate to higher levels of endogenous cytokines in association with parasite activation of the host's internal defence system, without obvious immediate adaptive signiWcance.…”

“…Although less well documented, selection of cool temperatures upon infection can also retard parasite development (e.g., Moore and Freehling 2002). However, alterations in host behavior may simply be a side-eVect of the infection and beneWt neither the host nor parasite (Campbell et al 2010;Kavaliers and Colwell 1992;Lefcort and Bayne 1991;Holmes and Zohar 1990;Minchella 1985;Ewald 1980).…”

Cockroach hosts in thermal gradients suppress parasite development

“…Under colder conditions, these workers live longer and produced fewer mature parasitoids than they would in a warmer environment (Muller and SchmidHempel 1993). Thermal preferences of snails (Biomphalaria glabrata) infected with schistosomes are also cooler than those of uninfected conspecifics (Lefcort and Bayne 1991). While the developmental effects of such preferences on the parasite were not investigated, it is reasonable to hypothesize negative effects (Blankespoor et al 1989; but see Chernin 1967).…”