Measuring Behavior 2005: Zemek and Socha

Searching for diel rhythmicity in behavioral data collected by The Observer

R. Zemek and R. Socha

Department of experimental ecology, Institute of Entomology, Èeské Budìjovice, Czech Republic

Biological rhythms are usually studied using various activity monitors like infrared sensors. These electronic devices can be used for automated recording of locomotion but not for complex behavioral activities like feeding, especially in small objects like insects. This paper describes how to perform simple chronobiological analysis of data obtained by The Observer^® (Noldus Information Technology bv, The Netherlands) using feeding behavior of the firebug, Pyrrhocoris apterus (Heteroptera) as an example.

A two-week study of bugs’ behavior was carried out under constant laboratory conditions. Since direct continuous observation would not be possible for such a long period including the scotophase, the arena with bugs was recorded by infra-red-sensitive CCD video camera connected to a time-lapse video recorder via VITC generator. Each video cassette represented a 24-hours record. Data on feeding activities were obtained from videotaped recordings using The Observer 3.0 with Support Package for Video Tape Analysis. For further analysis raw observation data files (*.ODF) were used.

The files were merged and time values were first converted into angles where a period of 24h corresponds to a full turn of 360 degrees. Hence time t is converted to an angle as 360t/1440 where t is in minutes. Data for each experimental group were pooled and the mean vector r was calculated. Its rectangular coordinates served to derive the mean or peak time of feeding activity. Calculations and plotting of 14-days ethograms and circular graphs were made using Fudgit and Gnuplot programs under Linux. Finally, randomization test was applied to examine whether there is statistical evidence of non-randomness of activity or whether the activity is uniformly distributed throughout the day-night cycle. This test was performed using a PASCAL program RanDir originally developed by Dr. Nachman for testing
orientation of organisms.

The study was supported by grant No. 206/03/0016 from the Grant Agency of the Czech Republic.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.