An experimental heat wave changes immune defense and life history traits in a freshwater snail
Article first published online: 10 DEC 2013
© 2013 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
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Ecology and Evolution
Volume 3, Issue 15, pages 4861–4871, December 2013
How to Cite
Ecology and Evolution 2013; 3(15): 4861–4871
- Issue published online: 10 DEC 2013
- Article first published online: 10 DEC 2013
- Manuscript Accepted: 11 OCT 2013
- Manuscript Revised: 8 OCT 2013
- Manuscript Received: 1 AUG 2013
- Emil Aaltonen Foundation
- Swiss National Science Foundation. Grant Numbers: 31003A, 140876, 31003A, 129961
- Global warming;
- immune function;
- life history traits;
- Lymnaea stagnalis ;
- resource allocation.
The predicted increase in frequency and severity of heat waves due to climate change is expected to alter disease dynamics by reducing hosts' ability to resist infections. This could take place via two different mechanisms: (1) through general reduction in hosts' performance under harsh environmental conditions and/or (2) through altered resource allocation that reduces expression of defense traits in order to maintain other traits. We tested these alternative hypotheses by measuring the effect of an experimental heat wave (25 vs. 15°C) on the constitutive level of immune defense (hemocyte concentration, phenoloxidase [PO]-like activity, antibacterial activity of hemolymph), and life history traits (growth and number of oviposited eggs) of the great pond snail Lymnaea stagnalis. We also manipulated the exposure time to high temperature (1, 3, 5, 7, 9, or 11 days). We found that if the exposure to high temperature lasted <1 week, immune function was not affected. However, when the exposure lasted longer than that, the level of snails' immune function (hemocyte concentration and PO-like activity) was reduced. Snails' growth and reproduction increased within the first week of exposure to high temperature. However, longer exposures did not lead to a further increase in cumulative reproductive output. Our results show that short experimental heat waves do not alter immune function but lead to plastic responses that increase snails' growth and reproduction. Thus, although the relative expression of traits changes, short experimental heat waves do not impair snails' defenses. Negative effects on performance get pronounced when the heat waves are prolonged suggesting that high performance cannot be maintained over long time periods. This ultimately reduces the levels of defense traits.