Predator-prey interactions are an important aspect of most ecosystems. As both predatory and prey, Daphnia magna serves as a unique model organism in aquatic ecology (Lampert 2006). D. magna consumes different types of appropriately sized particles, this includes algae, bacteria and protozoans (Lampert 2006). As prey, D. magna is well known for its morphological defences, that were developed in some individuals in response to certain predators (Lampert 2006). These defense mechanisms include helmets, crest, tail spines, and neck teeth (Lampert 2006). Other defensive behavioral responses can be triggered by the presences of chemical substances emitted in the near environment from predators (Pijanowska 1997). This leads to the question of how would the presence of a predator would affect behaviors such as feeding in D. magna.
Our hypothesis was that the presence of a predator will affect the feeding rate of D. magna. We predicted that if the D. magna is exposed to predators while feeding, they will have a slower feeding rate. We …show more content…
Three beakers were filled with 100 mL of river water and 1 mL of algae. Three other beakers were filled with 50 mL of water, 50 mL of predator cue from Lepomis macrochirus, and 1 mL of algae. Samples were taken from these beakers and pipetted into test tubes. These test tubes were placed in a fluorometer and measured for fluorescence, these values were recorded. Samples were then returned to their corresponding beaker. Ten similarly-sized D. magna were pipetted into each of the beakers for a period of 20 minutes. The D. magna were removed from the beakers and returned to a tank. Samples were taken from each of the beakers and placed in labeled test tubes. These test tubes were again placed in a fluorometer and measured. Units from the initial and final flourometer readings were converted from FIU to the number of cells using the following