title: Parasitized snails take the heat: a case of host manipulation?
abstract: Infection-induced changes in a host's thermal physiology can represent (1) a generalized host response to infection, (2) a pathological side-effect of infection, or (3), provided the parasite's development is temperature-dependent, a subtle case of host manipulation. This study investigates parasite-induced changes in the thermal biology of a first intermediate host infected by two castrating trematodes (genera Maritrema and Philophthalmus) using laboratory experiments and field surveys. The heat tolerance and temperatures selected by the snail, Zeacumantus subcarinatus, displayed alterations upon infection that differed between the two trematodes. Upon heating, snails infected by Maritrema sustained activity for longer durations than uninfected snails, followed by a more rapid recovery, and selected higher temperatures in a thermal gradient. These snails were also relatively abundant in high shore localities in the summer only, corresponding with seasonal elevated microhabitat temperatures. By contrast, Philophthalmus-infected snails fell rapidly into a coma upon heating and did not display altered thermal preferences. The respective heat tolerance of each trematode corresponded with the thermal responses induced in the snail: Maritrema survived exposure to 40°C, while Philophthalmus was less heat tolerant. Although both trematodes infect the same tissues, Philophthalmus leads to a reduction in the host's thermal tolerance, a response consistent with a pathological side effect. By contrast, Maritrema induces heat tolerance in the snail and withstood exposure to high heat. As the developmental rate and infectivity of Maritrema increase with temperature up to 25°C, one adaptive explanation for our findings is that Maritrema manipulates the snail's thermal responses to exploit warm microhabitats.
authors: Portobello Marine Laboratory, Department of Marine Science, University of Otago, Dunedin, New Zealand. amanda.bates@deakin.edu.au
authors: A E
authors: AE
authors: Bates
authors: F
authors: F
authors: Leiterer
authors: M L
authors: ML
authors: Wiedeback
authors: R
authors: R
authors: Poulin
references: Exp Parasitol. 1969 Aug;25(1):13-5
references: 5362576
references: Am J Physiol. 1976 Jul;231(1):198-203
references: 961860
references: Dis Aquat Organ. 2009 Nov 9;86(3):245-51
references: 20066959
references: Proc Biol Sci. 2002 Aug 7;269(1500):1599-607
references: 12184830
references: Nat Commun. 2010 May 04;1:14
references: 20975681
references: Naturwissenschaften. 2001 Apr;88(4):137-46
references: 11480701
references: Am J Trop Med Hyg. 1965 Nov;14(6):931-76
references: 5840648
references: Science. 1999 Sep 3;285(5433):1505-10
references: 10498537
references: Science. 2002 Jun 21;296(5576):2158-62
references: 12077394
references: J Theor Biol. 1980 Sep 7;86(1):169-76
references: 7464170
references: Parasitology. 1994;109 Suppl:S119-38
references: 7854846
references: Exp Parasitol. 1963 Dec;14:330-2
references: 14099845
references: J Parasitol. 2004 Apr;90(2):272-7
references: 15165049
references: Acta Physiol Scand. 1977 Oct;101(2):219-29
references: 303438
references: Oecologia. 1989 Sep;80(4):456-464
references: 28312828
references: Parasitology. 1991 Dec;103 Pt 3:357-62
references: 1780172
references: Parasitol Res. 2009 Oct;105(4):957-65
references: 19475423
references: Oecologia. 2002 Oct;133(2):261-266
references: 28547314
references: J Invertebr Pathol. 1971 Nov;18(3):412-8
references: 5151914
references: Comp Biochem Physiol A Comp Physiol. 1976;55(1):23-8
references: 8240
references: Biol Lett. 2010 Oct 23;6(5):669-73
references: 20375046
references: Parasitology. 2010 Sep;137(10):1487-91
references: 20500914