Lee Ehrman1, & Y.-K. Kim2
In a series of investigations into the development of discriminatory behavior in the D. paulistorum semispecies complex (Y.-K. Kim, L. Ehrman, and H. R. Koepfer, 1992, Behav. Genet. 22, 545-556; Y.-K. Kim, L. Ehrman, and H. R. Koepfer, 1996, Behav. Genet. 26, 15-25; Y.-K. Kim, H. R. Koepfer, and L. Ehrman, 1996, Behav. Genet. 26, 27-37), differences in courtship between control males and socially-isolated males (since egg deposition), representing each of the six D. paulistorum semispecies, were observed, and responses of females toward courtship from these two types of males scored. As controls, courtship elements and sequences did not unequivocally identify any given semispecies. However, for each element, there were consistent quantitative differences among semispecies: These six semispecies were significantly different from each other for all seven male courtship elements and for all four female responses, except standing. Developmental isolation was apparently sufficient enough to change courtship activities and mating performance: Socially-isolated males displayed more total courtship than did controls. Further, when mate competition for virgin females was observed between socially-isolated males and controls, such high levels of sexual activities led to impressive mating successes. Females simply preferred males that were more sexually active, in these instances, the socially-isolated ones. However, socially-isolated males from all six semispecies displayed homosexual behavior toward other males in our observation chambers. These findings suggest the possibility of changes in D. paulistorum brain structure. Thus, experience-dependent modification of brain structure (G. M. Technau, 1984, J. Neurogenet. 1, 113-126; A. Balling, G. M. Technau, and M. Heisenberg, 1987, J. Neurogenet. 4, 65-73; M. Heisenberg, M. Heusipp, and C. Wanke, 1995, J. Neurosci. 15, 1951-1960) during the development of individuals isolated from conspecifics will be observed.
Address: Division of Natural Sciences, State University of New York, 735 Anderson, Hill Road, Purchase, NY 10577, U. S. A.; TEL: 914-251-6671; FAX:, 914-251-6635; E-mail: lehrman@purvid.purchase.edu
1Division of Natural Sciences, State University of New York, Purchase, NY 10577, U. S. A. 2Department of Genetics, University of Georgia, Athens, GA 30602, U. S. A. 3Supported by Whitehall Foundation