Kathleen Siwicki, PhD

Professor
Biology Department
Swarthmore College

Pheromones and Memory of Unsuccessful Courtship

Dr. Siwicki launched her career as a Drosophila neurobiologist studying rhythmic expression of the period gene as a postdoctoral fellow in Jeff Hall’s lab. She studied with Dr. Hall from 1985 to 1989.

Dr. Siwicki’s research focus shifted to courtship behavior shortly after reading Dr. Hall’s influential 1994 review, The Mating of a Fly. While courtship is largely an innate behavior in male fruit flies, their sexual behavior can be influenced by unsuccessful attempts to court unreceptive females. When a male is paired with an unreceptive, mated female, he learns to suppress his courtship behavior toward this female, and it remains suppressed in subsequent pairings with virgins (Siegel and Hall, 1979). This experience-dependent modification of male courtship behavior is known as conditioned courtship suppression. Recent experiments in the Siwicki lab have addressed the role of female aphrodisiac pheromones in this learning and memory paradigm. Using genetic variants that produce flies with distinctive pheromonal blends, the researchers in the Siwicki lab have tested the requirement for specific compounds in both the acquisition and expression of males’ memory of unsuccessful courtship. On the one hand, the results suggest that some components of the female pheromonal profile are required to elicit the males’ memory of the aversive experience with mated females. On the other hand, work from the Siwicki lab has found that males can be trained to suppress their courtship by pheromonally depleted mated females. This suggests that they can acquire the memory even while courting females that lack the aphrodisiac pheromones in question. Additional behavioral studies with males carrying mutations or deletions of genes expressed selectively in chemosensory appendages further suggest a requirement for chemosensory signaling in both acquisition and expression of conditioned courtship suppression. The work discussed was completed by teams of talented Swarthmore undergraduates who have worked in her lab, in conjunction with the continuing influence of many colleagues who have shared the formative experiences of Brandeis neurogenetics.