Ralph Tollrian is academic chair for evolutionary Ecology and Biodiversity of animals at the Ruhr-University Bochum, Germany
Abstract:
The fascinating ability of organisms to estimate their predation risk, based on chemical cues released by predators, and to form adequate defences against these predators only when the defences are needed, has been reported from unicellular organisms to vertebrates. While protecting the individual, inducible defences bear the potential of influencing population dynamics and food webs. E.g., defences have been found to dampen predator-prey oscillations and to facilitate successful invasions.
Especially Daphnia has been found to respond with inducible defences to a range of their predators, even including plants. These defences may be specific to single predators or act as a multi-tool against different predators.
Despite their relevance not much is known about the internal pathways of the defence formation. First results show that in responses to different predators different neurophysiological pathways are involved. Genetic analyses identify a range of genes which are involved in defence formation and even the well-studied carapace of Daphnia still holds some surprises. But inducible defences are no safe harbour for prey organisms. New results indicate that they will be affected by man-made environmental changes with the potential for large-scale effects.  I will review inducible defences in Daphnia and present new results.