BLOCH QAZI, M.C.*; WOLFNER, M.F.; Gustavus Adolphus College, St. Peter, MN; Cornell University, Ithaca, NY: Egg-independent sperm release in female Drosophila melanogaster

In many species female sperm storage is an essential component of female fertility. One possible reason for this is that female sperm storage may help coordinate the relative availability of gametes thereby increasing fertilization efficiency. Sperm transfer, sperm storage and fertilization efficiency have been studied extensively in the fruit fly, Drosophila melanogaster. Since repeated matings are costly to females, we wished to test whether sperm release from storage was coordinated with egg presence and ovulation, which could prevent the waste of stored sperm. Using genetically identical females that were either normal or did not contain eggs, we compared sperm depletion patterns by counting the number of stored sperm remaining at several times after the start of egg laying. Significant numbers of sperm were released from storage whether or not eggs were present. Therefore, sperm release from storage is not tightly coupled with egg presence or ovulation. These results suggest that continuous sperm release may be a safeguard against missed fertilization opportunities and that costs associated with remating due to sperm depletion may not be as great as the costs associated with missed fertilization opportunities.