Sexual frustration and learning in fruit flies


By observing the mating rituals of fruit flies after different mating experiences, researchers have gained a greater understanding of how animals organize their behavioral responses in complex learning situations. The work is reported in the February 8 issue of Current Biology by Dr. Leslie Griffith, of Brandeis University, and colleagues at the University of Toronto.

Previous studies have demonstrated successful learning in the fruit fly (Drosophila melanogaster) under standardized laboratory conditions. In natural environments, however, the cues for learning are rarely clear cut. Animals are routinely presented with complex stimuli and must alter their behavior to give priority to the most relevant recent experience. To investigate how animals deal with learning multiple cues, we have explored the ability male fruit flies learn to discriminate between the pheromonal signals given off by different types of female flies.

Male courtship in fruit flies is a stereotyped set of behaviors that are stimulated by pheromones given off by female flies. Although courtship appears to be a "hard-wired" aspect of the male nervous system, the decision to initiate the behavior can be influenced by previous experience. This study demonstrates that Drosophila males can be trained to discriminate between different types of female pheromones: males will suppress courtship of the class of female that was associated in past experience with a failure to copulate. This "trainer-specific" learning is mediated by hydrocarbon olfactory cues and modifies the male's ability to subsequently respond to pheromones. Concurrent and serial presentation of different types of female pheromones demonstrated that the ability to retain the memory of a particular pheromonal cue could be modified by the order in which the cues were presented. Simultaneous presentation of two pheromone cues during training involving failed copulation resulted in males learning to avoid both types of females. If cues were presented serially, however, the formation of memory for the second cue actively suppressed retention of the memory for the first cue. This ability to modify learned behavior is essential for the successful navigation of experience-rich natural environments.

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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