Impacts of UV radiation on inducible defense traits of Daphnia pulex

Abstract

In aquatic environments predator threats can be present as chemical cues which can induce defensive traits in prey. Such predatory induced cues can be responsible for changes in morphology, life histories and behavior. Predator-induced plasticity has allowed for prey such as Daphnia pulex to avert capture by common predators such as Chaoborus larvae. Planktonic crustaceans offer a good opportunity to recreate aquatic ecosystem predator-prey dynamics such as Daphnia-Chaoborus interactions by use of microcosms in short term experiments. In this study two distinct clones Daphnia pulex were exposed to predatory cues, in order to observe the response rate of neckteeth formation in juvenile offspring. To test for the combined effect of kairomones, and an ever-present additional stressor, ultraviolet radiation (UVR) were applied in ecologically relevant levels in a two by two factorial experimental design. Results found that UVR exposure has a significant impact on the offspring’s ability to produce the defensive trait and resulted in inter-clonal differences in response rates to body size development. The use of a multifaceted design allowed for the investigation of the allocation of energy to abiotic and biotic stressors found in the natural environment of the key stone species Daphnia pulex.