Attraction of Flatworms at Various Hunger Levels Toward Cues from an Odonate Predator

Different hunger levels can modify a prey's antipredator behavior in the presence or absence of food. Satiated animals often forego foraging if a predator is nearby, whereas starved animals may risk a predator encounter to search for food. This study evaluated the influence of nutritional state on the behavior of the flatworm Dugesia dorotocephala in the presence of food, predator, and crushed conspecific cues. We found that flatworms are attracted to cues originating from a food source, crushed conspecifics, and a predator (dragonfly larva) compared with control cues. Among the different hunger level treatment groups, levels of satiation had no influence on activity levels but significantly influenced time spent close to and distance from the cue source. Flatworm movement toward predator cues emitted from dragonfly larvae is contrary to our expectations. These results suggest either a unique case of chemical mimicry from the dragonfly larvae or an inherent attraction of planarians to odonate predators that allows them to scavenge the remains of other odonate prey items.