Today, scientists at the Howard Hughes Medical Institute’s Janelia Research Campus have released a new and revolutionary resource. This new tool represents a giant leap forward in the study of motor control related to wing movements in fruit flies. This exciting innovation provides critical information about the underlying complex neural circuits. Together, these circuits constitute essential circuitry for the flight and courtship behaviors of these insects. The research published in the journal eLife describes how scientists tracked down single motor neurons to specific behaviors. This important, seminal work opens the door for future research into this area of motor control.
Scientist team leader Wyatt Korff, Senior Director of Team Projects at Janelia. Their’e primarily interested in the peculiar wing patterns that fruit fly females display. Through these behaviors we encounter some of the most fascinating examples of motor control found anywhere in the animal kingdom. The fine-tuning that fruit flies are able to achieve through small adaptations in flight posture can greatly impact their aerodynamic performance. Up close and personal, male D. simulans courtship song is a complex mix of sounds. To communicate, they do this through finely orchestrated wing-beat patterns unique to their species.
Mapping Neural Circuits
The authors carried out a massive effort to rigorously define the cell types in the dorsal dv VNC. These cell types are instrumental in the regulation of wing movement. They then characterized 196 unique cell types that could be targeted by 195 semi-stabilized fly driver lines present in their library. This detailed mapping provides important new clues about how these secreting cells might communicate. They send and receive neurological signals from your muscles to the brain and vice versa.
To further explore the unique function of motor neurons, the group focused on wing motor neurons using selective wing motor neuronal reagents. Their results revealed that stimulation of a steering muscle motor neuron, called i2, reduces wing stroke amplitude. This finding shines a bright light on the essential role i2 plays in wing motion. Activation of another related MN (called i1) had no impact on wing stroke amplitude. This distinction implies that different populations of neurons might underlie the control of different features of wing motion.
“Together the results lay the groundwork for a basic functional architecture of the neuronal circuitry controlling wing movements and provide an important resource for future investigations of the neurons underlying motor behavior,” – Wyatt Korff
Implications for Future Research
The new resource will accelerate research into the complex networks of neurons that coordinate all fruit fly behaviors. This encompasses the development of lateral flexion of the wings, coupling of the neck and, more interestingly, coordination of the halteres. Thanks to advances in techniques like optogenetics, scientists are now able to directly probe these premotor circuits. This will give them an opportunity to discover the important behaviors that contribute to fruit flies’ survival and reproduction.
Erica Ehrhardt, lead researcher on the project, stated that the importance of wing behaviors is a critical key to understanding motor control. She noted, “Wing behaviors comprise some of the most fascinating examples of motor control.” Through understanding these complex mechanisms, researchers aim to figure out the general rules that might govern these principles in different species.
“The library should enable researchers to probe the premotor circuits controlling the rich set of behaviors that require wing, neck or haltere coordination, such as flight or courtship,” – Wyatt Korff
Understanding Behavior through Neural Mechanisms
The research represents a unique chance to get to the bottom of how even slight changes in wing motion can translate to more pronounced behavioral effects. While in flight, small changes have significant aerodynamic impacts for fruit flies. Male fruit flies have to go through an elaborate courtship dance. They create a specific sound by beating their wings in a very controlled way to lure prospective mates.
Ehrhardt pointed out the importance of recognizing these behavioral nuances: “In flight, subtle adjustments can have large aerodynamic consequences, whereas on the ground male flies’ tightly patterned and subtle wing vibrations create a species-specific courtship song.” In so doing, this duality serves to underscore the critical importance of motor control to fitness—both survival and reproductive success.
PPD and criminal justice researchers are thrilled with this new ranging resource. They’re sure it’ll prove to be an indispensable resource for continued research seeking to untangle the intricacies of fruit fly motor control and behavior. If further research proves successful, it could provide important information about similar processes in other organisms.