Hormesis on life-history traits: is there such thing as a free lunch?
The term “hormesis” is used to describe dose–response relationships where the response is reversed between low and high doses of a stressor (generally, stimulation at low doses and inhibition at high ones). A mechanistic explanation is needed to interpret the relevance of such responses, but there does not appear to be a single universal mechanism underlying hormesis. When the endpoint is a life-history trait such as growth or reproduction, a stimulation of the response comes with costs in terms of resources. Organisms have to obey the conservation laws for mass and energy; there is no such thing as a free lunch. Based on the principles of Dynamic Energy Budget theory, we introduce three categories of explanations for hormesis that obey the conservation laws: acquisition (i.e., increasing the input of energy into the individual), allocation (i.e., rearranging the energy flows over various traits) and medication (e.g., the stressor is an essential element or acts as a cure for a disease or infection). In this discussion paper, we illustrate these explanations with cases where they might apply, and elaborate on the potential consequences for field populations.
KeywordsHormesis Energy budget Mechanisms Life-history traits Trade off
This research has been financially supported by the European Union under the 7th Framework Programme (project acronym CREAM, contract number PITN-GA-2009-238148).
- Baturo W, Lagadic L, Caquet T (1995) Growth, fecundity and glycogen utilization in Lymnaea palustris exposed to atrazine and hexachlorobenzene in freshwater mesocosms. Environ Toxicol Chem 14:503–511Google Scholar
- Hammers-Wirtz M, Ratte HT (2000) Offspring fitness in Daphnia: is the Daphnia reproduction test appropriate for extrapolating effects on the population level? Environ Toxicol Chem 19:1856–1866Google Scholar
- Kooijman SALM (Acc.) Waste to hurry: dynamic energy budgets explain the need of wasting to fully exploit blooming resources. Oikos (accepted for publication)Google Scholar
- Zimmer EI, Jager T, Ducrot V, Lagadic L, Kooijman SALM (2012) Juvenile food limitation in standardized tests—a warning to ecotoxicologists. Ecotoxicology 21:2195–2204Google Scholar