Abstract
BackgroundDrosophila larvae have been used as a model to study to genetic and cellular circuitries modulating behaviors. One of the challenges in behavioral study is the quantification of complex phenotypes such as locomotive behaviors. Experimental capability can be greatly enhanced by an automatic single-animal tracker that records an animal at a high resolution for an extended period, and analyzes multiple behavioral parameters.ResultsHere we present MaggotTracker, a single-animal tracking system for Drosophila larval locomotion analysis. This system controls the motorized microscope stage while taking a video, so that the animal remains in the viewing center. It then reduces the animal to 13 evenly distributed points along the midline, and computes over 20 parameters evaluating the shape, peristalsis movement, stamina, and track of the animal.To demonstrate its utility, we applied MaggotTracker to analyze both wild-type and mutant animals to identify factors affecting locomotive behaviors. Each animal was tracked for four minutes. Our analysis on Canton-S third-instar larvae revealed that the distance an animal travelled was correlated to its striding speed rather than the percentage of time the animal spent striding, and that the striding speed was correlated to both the distance and the duration of one stride. Sexual dimorphism was observed in body length but not in locomotive parameters such as speed. Locomotive parameters were affected by animal developmental stage and the crawling surface. No significant changes in movement speed were detected in mutants of circadian genes such as period (per), timeout, and timeless (tim). The MaggotTracker analysis showed that ether a go-go (eag), Shaker (Sh), slowpoke (slo), and dunce (dnc) mutant larvae had severe phenotypes in multiple locomotive parameters such as stride distance and speed, consistent with their function in neuromuscular junctions. Further, the phenotypic patterns of the K+ channel genes eag, Sh and slo are highly similar.ConclusionsThese results showed that MaggotTracker is an efficient tool for automatic phenotyping. The MaggotTracker software as well as the data presented here can be downloaded from our open-access site www.WormLoco.org/Mag.Electronic supplementary materialThe online version of this article (doi:10.1186/s12861-015-0062-0) contains supplementary material, which is available to authorized users.
Highlights
Drosophila larvae have been used as a model to study to genetic and cellular circuitries modulating behaviors
Drosophila larvae display a rich collection of locomotive behaviors such as peristaltic crawling, pausing, and turning [1,2]
Hardware components of MaggotTracker The hardware for MaggotTracker is composed of a digital camera, a dissecting microscope, a motorized stage, and a computer that controls the camera and the stage (Figure 1)
Summary
Drosophila larvae have been used as a model to study to genetic and cellular circuitries modulating behaviors. One of the challenges in behavioral study is the quantification of complex phenotypes such as locomotive behaviors. Experimental capability can be greatly enhanced by an automatic single-animal tracker that records an animal at a high resolution for an extended period, and analyzes multiple behavioral parameters. The fruit fly Drosophila melanogaster is a highly popular model organism for behavioral studies. Quantitative analysis of these behaviors is often needed to investigate the molecular and cellular circuitry modulating such behaviors. There are two types of systems providing such analysis: single-animal tracker and multi-animal tracker. A single-animal tracker often changes its position to follow one animal. Multi-animal trackers provide a higher throughput, and single-animal trackers enable a higher resolution. As singleanimal trackers can use a higher magnification, more phenotypic details can be extracted from the images and videos
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