EthoVision at the frontiers of research on fish behavior

 Though mainly used to track small rodents such as mice and rats, EthoVision, the computerized video-tracking system, is capable of tracking swim patterns of fish as well. The ability to track fish is important since zebrafish (Danio rerio) and the Japanese medaka (Oryzias latipes) may one day take over from rats as the most popular laboratory animals.
Reasons for this development are abundant. Both species are small and grow rapidly, with a short reproductive cycle and a large number of offspring per mating. This results in easy handling and cost efficiency. Furthermore, they are completely transparent, allowing internal organs and neurons to be visualized, they easily absorb compounds from the surrounding water and they can easily be mutagenized. More importantly, they are proven to share several genes with humans and model human biology closely. It is suggested that mental processes such as learning and memory are present, at least in zebrafish. Due to these advantageous characteristics, both medaka and zebrafish are used for investigations in genetics and developmental biology. In addition, zebrafish are frequently used for studies in behavioral biology and behavioral ecology. The behavioral output of zebrafish has only recently begun to receive attention and they are becoming more and more popular with behavioral research institutes and laboratories around the world. They are mainly used for investigation of behavioral changes induced by novel drugs or by substances such as alcohol. Frequently used test paradigms to achieve this include the novel tank test, the social preference test, the T-maze test and monitoring activity in a well plate.
The functionality of EthoVision tracking small fish in an open tank is demonstrated by research of Robert Gerlai, professor of psychology at the University of Toronto, Canada. In this study zebrafish participate in four different tests (novel open tank test, social preference test, aggression test and predator model test) and activity and locomotion are recorded manually as well as automatically with EthoVision. Comparison of the manually recorded data and the video-tracking data shows that EthoVision can reliably measure the location and intensity of swim in zebrafish.
Due to their small size and transparency the fish larvae can easily be individually placed and observed in wells of a 96-well plate. EthoVision is capable of tracking and quantifying swim patterns of these 96 fish larvae simultaneously. This greatly increases the throughput of experiments. For instance, this application is used when testing the effects of a substance, each row of the plate corresponding with another concentration of this substance.
To ensure robust tracking of small fish (larvae) in a well plate, Tracksys ltd developed a tower filming system, especially suitable for use in combination with EthoVision. The system consists of an infra-red light box with a holder on top and a rigid stand with an IR-sensitive camera positioned right above the holder. The holder is suitable for different sized well plates and ensures that the plate is always in exactly the same position. The rigid stand keeps the camera in the same position. The combination of an IR light source and an IR-sensitive camera allows tracking in the dark. When used in combination with EthoVision, small fish (larvae) housed in well plates can be reliably tracked, without repositioning of the plates or camera. For more information about this tower filming system, please contact us.
The functionality of EthoVision tracking zebrafish larvae in a 96-well plate can be illustrated by an investigation conducted by Scott C. Baraban, associate professor in the Neuroscience Program at the University of California, San Francisco and his co-workers. In this research zebrafish larvae were either treated or not treated with a common convulsant agent, pentylenetetrazole (PTZ), and individually placed in wells of a 96-well plate. Subsequently, EthoVision automatically tracked their paths and calculated the total distance traveled and the percentage of time spent moving. Besides the conclusion that the tested substance induced behavioral seizure activity in zebrafish that closely resembles that reported in rodents, this research illustrated that EthoVision is the right instrument to automatically measure seizure behaviors.
For further information about the use of medaka and zebrafish with EthoVision, please consult the following publications:
Anichtchik, O.V.; Kaslin, J.; Peitsaro, N.; Scheinin, M.; Panula, P. (2004). Neurochemical and behavioural changes in zebrafish Danio rerio after systemic administration of 6-hydroxydopamine and 1-methyl-4-phenyl-1,2,3,4-tetrahydroxyridine. Journal of Neurochemistry, 88, 443-453. Baraban, S.C.; Taylor, M.R.; Castro, P.A.; Baier, H. (2005). Pentylenetetrazole induced changes in zebrafish behavior, neural activity and c-fos expression. Neuroscience, 131, 759-768. Becker, C.G.; Lieberoth, B.C; Morellini, F.; Feldner, J.; Becker, T.; Schachner, M. (2004). L1.1 is involved in spinal cord regeneration in adult zebrafish. The Journal of Neuroscience, 24, 7837-7842.  Gerlai, R. (2005). Event recording and video-tracking: towards the development of high throughput zebrafish screens. Paper presented at Measuring Behavior 2005, 5th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands. Ishikawa, Y. (2000). Medakafish as a model system for vertebrate developmental genetics. BioEssays, 22, 487-495. Peitsaro, N.; Kaslin, J.; Anichtchik, O.V.; Panula, P. (2003). Modulation of the histaminergic system and behaviour by fluoromethylhistidine in zebrafish. Journal of Neurochemistry, 86, 432-441. Pritchard, V.L.; Lawrence, J.; Butlin, R.K.; Krause, J. (2001). Shoal choice in zebrafish, Danio rerio: the influence of shoal size and activity. Animal Behavior, 62, 1085-1088.