O.H. Spieser, W. Scholz, G. Staaks and D. Baganz
Department of Biology and Ecology of Fishes, Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
Using an automated behaviour measuring system we investigated the influence of the naturally occuring cyanotoxin Microcystin-LR on zebrafish. The measuring system BehavioQuant® was designed to record behavioural parameters of different organisms. It is able to register up to 200 untagged objects and makes use of the integrative whole-organism behavorial response by recording and quantifying the spontaneous locomotor activity of all observed objects. The measured characteristics of objects (location, direction of movements and speed) make it possible to describe certain behavioural patterns similar to an ethogram. The concrete parameters in our experiental design with fish were: swimming speed (motility), count of turnings, swimming depth, horizontal location and individual distances.
The animals were observed by a video camera. The three dimensional movements of organisms were in this case projected on a two dimensional area. The video signal was processed by a digitizer board inside an Intel-based computer system. With a frequency of 25 s-1 every picture of the experimental chamber was in real time compared point-by-point with a background reference picture, which can be generated in preset intervals. The x-y positions of recognized objects are written to disk for every measuring interval.
An online or offline working software component reconstructs the pathways of the objects and allows to calculate the means or distributions of mentioned parameters in user definable time intervals. The online data analysis proceeds during breaks between two measuring intervals, the offline version is to be used in case of continiouse observation on an a separate computer with the collected data sets. Furthermore some statistics like mean, median, standard deviation, variance, U- and t-tests can be calculated by the software package. With an external statistical program methods of time series analysis can be included.
To ensure the continuous observation of individuals and register movements during the especially interesting spaces of dawn, dusk and night the system was adapted with cameras which are able to handle normal as well as infrared light. The system can be used with up to 16 observation units which are then sequentially processed by the digitizer board.
We are using the BehavioQuant system to determine the influences of toxic chemicals on aquatic organisms at the behavioural level. Thereby changes in behaviour of animals can often indicate very low levels of stress which don't come along with pathologic effects.
The effects and the toxic potential of Microcystin-LR, a cyanobacteria toxin which may occur in eutrophic lakes during the mass developments of these algae, was investigated regarding the behaviour of zebrafish (Brachydanio rerio). We worked with four concentrations of a polluted lakewater and one control group. A schoal of 7 individuals was kept in each of the test aquaria. They had a 12 hours day and night and were fed twice a day automatically. Once a day the aquaria were cleaned. Under the influence of relevant concentrations of the substance the fish showed characteristic changes in behaviour. A significant relation between concentration and effects was found. The maximum of activity during the day shifted from the early morning hours towards the afternoon. The response to food over the whole day and the spawning activities during the morning hours were dramatically reduced at the higher concentrations.
BehavioQuant® has been developed by the GSF-Research-Center of Environment and Health and Metacom GmbH, Munich.