Tracking the movement of C. elegans is a well-stablished route to identify and refine understanding of microcircuits that control behaviour. Over several years a number of different experimental platforms and associated software for video analysis have been developed to facilitate this (1). To contribute to this we have designed a relatively low cost modular system for real-time tracking and analysis of worm locomotory behaviour. TrakBox (EMbody Biosignals Ltd) (2) is assembled from 3-D printed components in which a robotic arm moves a USB camera to maintain the animal being tracked within a target site. Reverse kinematics is used to decode the coordinates of the worm as it moves around the plate with continuous tracking being possible for at least 24 h. Videos may also be captured but are not required for the behavioural analyses. Advanced signal processing filters and corrects the worm position over time and constantly updates a series of behaviour parameters calculated 'on the fly'. TrakBox software derives parameters over the entire course of tracking that describe worm position, instantaneous velocity, instantaneous direction of travel, dwelling and roaming times and number of reversals. The user may define the behavioural parameters of interest and they may be displayed as a graphical representation. As a proof of concept we compared the behaviour of N2 and a mod-1 mutant. mod-1 encodes a serotonin-gated chloride channel and a loss of function mutant exhibits increased exploration and extended roaming time (3). TrakBox efficiently extracted this phenotype by analysing roaming/dwelling fractions of time, velocity and reversal events and their duration. Thus, we show TrakBox permits discrete real-time analysis of C. elegans locomotory behaviour that circumvents the need for post-hoc analysis of videos. This experimental platform also has applications for investigation of the effects of drugs on behaviour, may be applied to analysis of other microscopic nematodes including pest species, have uses in field studies and provide an affordable option for class room demonstration of C. elegans biology. (1) Husson, S. J. et al. Keeping track of worm trackers (September 10, 2012), WormBook, ed. (2) http://embody-biosignals.com/ (3) Flavell, S. W., N. Pokala, E. Z. Macosko, D. R. Albrecht, J. Larsch and C. I. Bargmann (2013). "Serotonin and the neuropeptide PDF initiate and extend opposing behavioral states in C. elegans." Cell 154(5): 1023-1035

Affiliations:
- Warwick Engineering in Biomedicine, University of Warwick (UK)
- Biological Sciences, University of Southampton, Southampton (UK), Southampton, GB