Can you imagine looking for a destination without a GPS, visual landmarks, or even street signs?

This is the reality for fruit flies, as they search for food or a mate. Researchers have uncovered different cues that influence these searches, but until now, haven’t yet understood how individual directional cues and search movements are used together.

Findings from researchers in Drexel’s School of Biomedical Engineering, Science and Health Systems provide clarity on how flies find food, and also may help answer broader questions about how the ways that insects and animals search for food influences broader food ecology and the environment.

LIGHT_SENSE

The diagram above depicts a fly’s behavior in a small, circular arena. There is no light. Flies spend most of their time on the border and make occasional forays to the center (green lines). When a red light, which the flies cannot see but which activates genetically engineered olfactory neurons is turned on, flies think that there is an attractive odor in the center and start circling the center.

The team converted the flies’ olfactory nerve cells that usually respond to odors into light-sensing cells to detail the paths of flies as they find food, leave and attempt to return back to the food. To do this, the team projected light in a small region of a larger area to stimulate receptor nerve cells that control fruit flies’ sense of smell.

The study showed how non-orienting movements, such as slowing down significantly and turning frequently to stay in an area, can be an effective mechanism for finding resources when directional cues are absent.

“Non-orienting movements are also found in expert navigators, such as desert ants. Once they are near their home, they depend on these movements to get there,” says Associate Professor Vikas Bhandawat.

“One of the main takeaways here is that smell — as a sensation in the near past — is an effective sensory cue for flies, and likely many other animals,” adds lead author Liangyu Tao, a graduate student in the School of Biomedical Engineering, Science and Health Systems.