Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quick Getaway: How Flies Escape Looming Predators

10.06.2014

When a fruit fly detects an approaching predator, the fly can launch itself into the air and soar gracefully to safety in a fraction of a second. But there's not always time for that.

Some threats demand a quicker getaway. New research from scientists at Howard Hughes Medical Institute's Janelia Research Campus reveals how a quick-escape circuit in the fly's brain overrides the fly's slower, more controlled behavior when a threat becomes urgent.


Photo by Igor Siwanowicz, HHMI/Janelia.

Scientists at HHMI's Janelia Research Campus discover how a quick-escape circuit in the fly's brain overrides the fly's slower, more controlled behavior when a threat becomes urgent.

“The fly's rapid takeoff is, on average, eight milliseconds faster than its more controlled takeoff,” says Janelia group leader Gwyneth Card. “Eight milliseconds could be the difference between life and death.”

Card studies escape behaviors in the fruit fly to unravel the circuits and processes that underlie decision making, teasing out how the brain integrates information to respond to a changing environment. Her team's new study, published online June 8, 2014, in the journal Nature Neuroscience, shows that two neural circuits mediate fruit flies' slow-and-stable or quick-but-clumsy escape behaviors. Card, postdoctoral researcher Catherine von Reyn, and their colleagues find that a spike of activity in a key neuron in the quick-escape circuit can override the slower escape, prompting the fly to spring to safety when a threat gets too near.

... more about:
»Looming »behavior »circuit »escape »fiber »flies »fly »neurons »stimulus

A pair of neurons -- called giant fibers -- in the fruit fly brain has long been suspected to trigger escape. Researchers can provoke this behavior by artificially activating the giant fiber neurons, but no one had actually demonstrated that those neurons responded to visual cues associated with an approaching predator, Card says. She was curious how the neurons could be involved in the natural behavior if they didn't seem to respond to the relevant sensory cues, so she decided to test their role.

Genetic tools developed in the lab of Janelia executive director Gerald Rubin enabled Card's team to switch the giant fiber neurons on or off, and then observe how flies responded to a predator-like stimulus. They conducted their experiments in an apparatus developed in Card's lab that captures videos of individual flies as they are exposed to a looming dark circle. The image is projected onto a hemispheric surface and expands rapidly to fill the fly's visual field, simulating the approach of a predator. “It's really like a domed IMAX for the fly,” Card explains. A high-speed camera records the response at 6,000 frames per second, allowing Card and her colleagues to examine in detail the series of events that make up the fly's escape.

To ensure their experiments were relevant to fruit flies' real-world experiences, Card teamed with fellow Janelia group leader Anthony Leonardo to record and analyze the trajectories and acceleration of damselflies – natural predators of the fruit fly – as they attacked. They designed their looming stimulus to mimic these features. “We wanted to make sure we were really challenging the animal with something that was like a predator attack,” Card says.

By analyzing more than 4,000 flies, Card and her colleagues discovered two distinct responses to the simulated predator: long and short escapes. To prepare for a steady take-off, flies took the time to raise their wings fully. Quicker escapes, in contrast, eliminated this step, shaving time off the take-off but often causing the fly to tumble through the air.

When the scientists switched off the giant fiber neurons, preventing them from firing, flies still managed to complete their escape sequence. “On a surface level evaluation, silencing the neuron had absolutely no effect,” Card says. “You can do away with this neuron that people thought was fundamental to this escape behavior, and flies still escape.” Shorter escapes, however, were completely eliminated. Flies without active giant fiber neurons invariably opted for the slower, steadier escape. In contrast, when the scientists switched giant fiber neurons on in the absence of a predator-like stimulus, flies enacted their quick-escape behavior. The evidence suggested the giant fiber neurons were involved only in short escapes, while a separate circuit mediated the long escapes.

Card and her colleagues wanted to understand how flies decide when to sacrifice stability in favor of a quicker response. To learn more, Catherine von Reyn, a postdoctoral researcher in Card's lab, set up experiments in which she could directly monitor activity in the giant fiber neurons. Surprisingly, she discovered that the giant fibers were not only active in short-mode escape, but also during some of the long-mode escapes. The situation was more complicated than their genetic experiments had suggested. “Seeing the dynamics of the electrophysiology allowed us to understand that the timing of the spike is important is determining the fly's choice of escape behavior,” Card says.

Based on their data, Card and von Reyn propose that a looming stimulus first activates a circuit in the brain that initiates a slow escape, beginning with a controlled lift of the wings. When the object looms closer, filling more of the fly's field of view, the giant fiber activates, prompting a more urgent escape. “What determines whether a fly does a long-mode or a short-mode escape is how soon after the wings go up the fly kicks its legs and it starts to take off,” Card says. “The giant fiber can fire at any point during that sequence. It might not fire at all – in which case you get this nice long, beautifully choreographed takeoff. It might fire right away, in which case you get an abbreviated escape.” The more quickly an object approaches, the sooner the giant fiber is likely to fire, increasing the probability of a short escape.

Card remains curious about many aspects of escape behavior. How does a fly calculate the orientation of a threat and decide in which direction to flee, she wonders. What makes a fly decide to initiate a takeoff as opposed to other evasive maneuvers? The relatively compact circuits that control these sensory-driven behaviors provide a powerful system for exploring the mechanisms that animals use to selecting one behavior over another, she says. “We think that you can really ask these questions at the level of individual neurons, and even individual spikes in those neurons.”

Jim Keeley | newswise
Further information:
http://www.hhmi.org

Further reports about: Looming behavior circuit escape fiber flies fly neurons stimulus

More articles from Life Sciences:

nachricht Gene switch may repair DNA and prevent cancer
12.02.2016 | Institute for Integrated Cell-Material Sciences at Kyoto University

nachricht New method opens crystal clear views of biomolecules
11.02.2016 | Deutsches Elektronen-Synchrotron DESY

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Production of an AIDS vaccine in algae

Today, plants and microorganisms are heavily used for the production of medicinal products. The production of biopharmaceuticals in plants, also referred to as “Molecular Pharming”, represents a continuously growing field of plant biotechnology. Preferred host organisms include yeast and crop plants, such as maize and potato – plants with high demands. With the help of a special algal strain, the research team of Prof. Ralph Bock at the Max Planck Institute of Molecular Plant Physiology in Potsdam strives to develop a more efficient and resource-saving system for the production of medicines and vaccines. They tested its practicality by synthesizing a component of a potential AIDS vaccine.

The use of plants and microorganisms to produce pharmaceuticals is nothing new. In 1982, bacteria were genetically modified to produce human insulin, a drug...

Im Focus: The most accurate optical single-ion clock worldwide

Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock which attains an accuracy which had only been predicted theoretically so far. Their optical ytterbium clock achieved a relative systematic measurement uncertainty of 3 E-18. The results have been published in the current issue of the scientific journal "Physical Review Letters".

Atomic clock experts from the Physikalisch-Technische Bundesanstalt (PTB) are the first research group in the world to have built an optical single-ion clock...

Im Focus: Goodbye ground control: autonomous nanosatellites

The University of Würzburg has two new space projects in the pipeline which are concerned with the observation of planets and autonomous fault correction aboard satellites. The German Federal Ministry of Economic Affairs and Energy funds the projects with around 1.6 million euros.

Detecting tornadoes that sweep across Mars. Discovering meteors that fall to Earth. Investigating strange lightning that flashes from Earth's atmosphere into...

Im Focus: Flow phenomena on solid surfaces: Physicists highlight key role played by boundary layer velocity

Physicists from Saarland University and the ESPCI in Paris have shown how liquids on solid surfaces can be made to slide over the surface a bit like a bobsleigh on ice. The key is to apply a coating at the boundary between the liquid and the surface that induces the liquid to slip. This results in an increase in the average flow velocity of the liquid and its throughput. This was demonstrated by studying the behaviour of droplets on surfaces with different coatings as they evolved into the equilibrium state. The results could prove useful in optimizing industrial processes, such as the extrusion of plastics.

The study has been published in the respected academic journal PNAS (Proceedings of the National Academy of Sciences of the United States of America).

Im Focus: New study: How stable is the West Antarctic Ice Sheet?

Exceeding critical temperature limits in the Southern Ocean may cause the collapse of ice sheets and a sharp rise in sea levels

A future warming of the Southern Ocean caused by rising greenhouse gas concentrations in the atmosphere may severely disrupt the stability of the West...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Symposium on Climate Change Adaptation in Africa 2016

12.02.2016 | Event News

Travel grants available: Meet the world’s most proficient mathematicians and computer scientists

09.02.2016 | Event News

AKL’16: Experience Laser Technology Live in Europe´s Largest Laser Application Center!

02.02.2016 | Event News

 
Latest News

LIGO confirms RIT's breakthrough prediction of gravitational waves

12.02.2016 | Physics and Astronomy

Gene switch may repair DNA and prevent cancer

12.02.2016 | Life Sciences

Using 'Pacemakers' in spinal cord injuries

12.02.2016 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>