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A Novel Method for Tracking Individuals of Fruit Fly Swarms Flying in a Laboratory Flight Arena.

Cheng XE, Qian ZM, Wang SH, Jiang N, Guo A, Chen YQ - PLoS ONE (2015)

Bottom Line: We found that there exists an asymptotic distance between fruit flies in swarms as the population density increases.Further, we discovered the evidence for repulsive response when the distance between fruit flies approached the asymptotic distance.Overall, the proposed tracking system presents a powerful method for studying flight behaviours of fruit flies in a three-dimensional environment.

View Article: PubMed Central - PubMed

Affiliation: School of Computer Science, Shanghai Key Laboratory of Intelligent Information Processing, Fudan University, Shanghai, China; Jingdezhen Ceramic Institute, Jingdezhen, China.

ABSTRACT
The growing interest in studying social behaviours of swarming fruit flies, Drosophila melanogaster, has heightened the need for developing tools that provide quantitative motion data. To achieve such a goal, multi-camera three-dimensional tracking technology is the key experimental gateway. We have developed a novel tracking system for tracking hundreds of fruit flies flying in a confined cubic flight arena. In addition to the proposed tracking algorithm, this work offers additional contributions in three aspects: body detection, orientation estimation, and data validation. To demonstrate the opportunities that the proposed system offers for generating high-throughput quantitative motion data, we conducted experiments on five experimental configurations. We also performed quantitative analysis on the kinematics and the spatial structure and the motion patterns of fruit fly swarms. We found that there exists an asymptotic distance between fruit flies in swarms as the population density increases. Further, we discovered the evidence for repulsive response when the distance between fruit flies approached the asymptotic distance. Overall, the proposed tracking system presents a powerful method for studying flight behaviours of fruit flies in a three-dimensional environment.

No MeSH data available.


Detecting.(a) The image at the left was filmed by a back-lit camera and the patch marked by the green rectangle was zoomed at the right. (b) The patch was overlaid with red blobs which were detected using background subtraction. (c) The patch was overlaid with refined blobs in which the pixels of wings were removed. (d) The result of fitting each blob with an ellipse.
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pone.0129657.g002: Detecting.(a) The image at the left was filmed by a back-lit camera and the patch marked by the green rectangle was zoomed at the right. (b) The patch was overlaid with red blobs which were detected using background subtraction. (c) The patch was overlaid with refined blobs in which the pixels of wings were removed. (d) The result of fitting each blob with an ellipse.

Mentions: Previous studies [10–14, 23] have demonstrated that the illumination was usually provided by front-lighting in laboratory. The front-lighting means lights and cameras are placed at the same side of the targets. It has the advantage of showing the rich texture of targets and the background. The rich texture however makes target detection and resolving body’s pixels very difficult. The back-lighting is the opposite, i.e. the targets are imaged as silhouettes against plain white background. In our problem, we moved the lights to the side of targets opposite the cameras, meaning that targets were back-lit in camera views. Fig 2a shows an image in which fruit flies were back-lit in the camera view. We presented a simple and efficient detecting approach in this paper. The proposed approach makes full use of the different levels of transparency between the wings and body of a fruit fly, in which the pixels of a fly’s wings have higher intensities than pixels of its body. The proposed detecting approach segments an image into blobs. Each blob is an image area with pixels’ locations and intensities, and each blob represents the observation of a certain fruit fly in a camera view. To simplify notation, all definitions in this section ignore subscripts for cameras and moments.


A Novel Method for Tracking Individuals of Fruit Fly Swarms Flying in a Laboratory Flight Arena.

Cheng XE, Qian ZM, Wang SH, Jiang N, Guo A, Chen YQ - PLoS ONE (2015)

Detecting.(a) The image at the left was filmed by a back-lit camera and the patch marked by the green rectangle was zoomed at the right. (b) The patch was overlaid with red blobs which were detected using background subtraction. (c) The patch was overlaid with refined blobs in which the pixels of wings were removed. (d) The result of fitting each blob with an ellipse.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4470659&req=5

pone.0129657.g002: Detecting.(a) The image at the left was filmed by a back-lit camera and the patch marked by the green rectangle was zoomed at the right. (b) The patch was overlaid with red blobs which were detected using background subtraction. (c) The patch was overlaid with refined blobs in which the pixels of wings were removed. (d) The result of fitting each blob with an ellipse.
Mentions: Previous studies [10–14, 23] have demonstrated that the illumination was usually provided by front-lighting in laboratory. The front-lighting means lights and cameras are placed at the same side of the targets. It has the advantage of showing the rich texture of targets and the background. The rich texture however makes target detection and resolving body’s pixels very difficult. The back-lighting is the opposite, i.e. the targets are imaged as silhouettes against plain white background. In our problem, we moved the lights to the side of targets opposite the cameras, meaning that targets were back-lit in camera views. Fig 2a shows an image in which fruit flies were back-lit in the camera view. We presented a simple and efficient detecting approach in this paper. The proposed approach makes full use of the different levels of transparency between the wings and body of a fruit fly, in which the pixels of a fly’s wings have higher intensities than pixels of its body. The proposed detecting approach segments an image into blobs. Each blob is an image area with pixels’ locations and intensities, and each blob represents the observation of a certain fruit fly in a camera view. To simplify notation, all definitions in this section ignore subscripts for cameras and moments.

Bottom Line: We found that there exists an asymptotic distance between fruit flies in swarms as the population density increases.Further, we discovered the evidence for repulsive response when the distance between fruit flies approached the asymptotic distance.Overall, the proposed tracking system presents a powerful method for studying flight behaviours of fruit flies in a three-dimensional environment.

View Article: PubMed Central - PubMed

Affiliation: School of Computer Science, Shanghai Key Laboratory of Intelligent Information Processing, Fudan University, Shanghai, China; Jingdezhen Ceramic Institute, Jingdezhen, China.

ABSTRACT
The growing interest in studying social behaviours of swarming fruit flies, Drosophila melanogaster, has heightened the need for developing tools that provide quantitative motion data. To achieve such a goal, multi-camera three-dimensional tracking technology is the key experimental gateway. We have developed a novel tracking system for tracking hundreds of fruit flies flying in a confined cubic flight arena. In addition to the proposed tracking algorithm, this work offers additional contributions in three aspects: body detection, orientation estimation, and data validation. To demonstrate the opportunities that the proposed system offers for generating high-throughput quantitative motion data, we conducted experiments on five experimental configurations. We also performed quantitative analysis on the kinematics and the spatial structure and the motion patterns of fruit fly swarms. We found that there exists an asymptotic distance between fruit flies in swarms as the population density increases. Further, we discovered the evidence for repulsive response when the distance between fruit flies approached the asymptotic distance. Overall, the proposed tracking system presents a powerful method for studying flight behaviours of fruit flies in a three-dimensional environment.

No MeSH data available.