Microanalysis of courtship behaviour in Drosophila melanogaster

B. I. Arthur¹, Jr. and M. S. Magnusson²

¹Zoologisches Museum, Universitaet Zuerich, Zurich, Switzerland
²Human Behavior Laboratory, University of Iceland, Reykjavik, Iceland

The essential progressive sequence of fixed action patterns in the courtship behavior of Drosophila melanogaster is well established. However, given the small dimensions of the fly and the rapidity of its actions the finer structure of its behavior and interactions is less known. We therefore video-recorded the courtship of male-female pairs at a frame rate of 30/s and with image quality allowing visual identification of minute behavioral elements. This enabled us to identify and register precisely the times of occurrence of known elements of courtship behavior, but also of new behavioral elements invisible to the unaided eye. The coding thus resulted in real-time behavior records of considerable complexity. Previous studies of Drosophila melanogaster courtship behavior have mostly reported only the coarse elements of male activity and totally neglected female activity and the interactive nature of courtship. We guessed that the finer structure of such behavior might involve hidden patterns of value in courtship interaction. We therefore searched for possible hidden intra- and inter-individual temporal patterns using the Theme program to process the data from all the male-female dyads. It performs an intensive search for a particular but very large class of temporal patterns called t-patterns. This pattern type was specially developed for the detection of hidden structure in real-time behavior and interaction records. We detected special patterns characteristic of female receptivity that were dependent on their reproductive status and also of abnormal courtship displayed by a male carrying a mutant allele of the fruitless gene compared to normal male patterns. These analyses have revealed patterns whose appearance and disappearance typify the development of female sexual behavior and its subsequent modification after mating. Additionally, we found that patterns from dyads with fruitless mutant males showed less interaction with partner compared to normal males. T-patterns provide a promising approach to the usually elusive phenotyping of behavior and will facilitate studies into its molecular genetics basis.

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.

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