The role of yolk protein dynamics and predator kairomones for the life history of Daphnia magna

Resource allocation for reproduction of daphniids is strongly determined by the production of yolk protein. It is the main process channeling material into the reproductive pool of the animals. My investigations of yolk protein dynamics provided evidence that Daphnia are able to exhibit flexible brood reduction behavior and that individuals do not use all of the produced yolk protein for reproduction. The animals show parental optimism, meaning that they start to produce more material for offspring than they actually release. Yolk protein dynamics were influenced by predator-released kairomones. Fish kairomones influenced the beginning of yolk production resulting in a shorter time until first reproduction. In addition, daphniids exposed to fish kairomones used more of the produced yolk protein for reproduction than did control animals. The fish kairomone did not influence the rate of yolk production. In contrast, Chaoborus kairomones influenced the rate of yolk production, but did not change either the beginning of yolk production or the proportion of yolk that was used for egg production. The yolk protein dynamics of daphniids and their ability to exhibit flexible brood reduction behavior can help to explain kairomone-induced life history modifications of daphniids in numerous life history experiments