Immune attack makes female flies dump their sperm store

UCF Biology professor Ken Fedorka has recently discovered that if a female fruit fly receives sperm from an infected male fly she will likely dump the sperm. His research paper (read it here) also explains how the sperm can suffer if the male or female fly is sick.

Sperm viability has been associated with the degree of promiscuity across species, as well as the degreeof reproductive success within species. Thus, sperm survival within the female reproductive tract likelyplays a key role in how mating systems evolve. In the fruit fly, Drosophila melanogaster, however, theextent and cause of sperm death has been the subject of recent debate. Here, we assess sperm deathwithin the female reproductive tract of D. melanogaster following single and multiple matings in order toelucidate the extent of death and its potential mechanisms, including an acute female response tomating, female age and/or sperm senescence. We found no evidence that sperm viability was influencedby an acute female response or female age. We also found that rival ejaculates did not influence viability,supporting recent work in the system. Instead, the majority of death appears to be due to the aging ofmale gametes within the female, and that at least some dead resident sperm remain in the female aftermultiple mating. In contrast to earlier in vivo work, we found that overall sperm death was minimal(8.7%), indicating viability should have a negligible influence on female remating rates.

Fedorka on his research:

Like the organisms I study, my research program has also become an amalgamation of traits, drawing theory and technique from several different disciplines within evolutionary biology, including sexual selection, ecological immunology and evolutionary ecology.  These disciplines have provided me with the tools needed to address a diversity of questions regarding adaptive evolution. Some of my current research interests include:

• The role of the thermal environment in shaping innate immunity.
• The role of the Y-chromosome in constraining immune system evolution
• The role of the mating environment in modifying male ejaculate composition
• The role of gene flow asymmetry in constraining species range expansion
• The antagonistic coevolution of reproductive and immune systems
• Terminal investment and the production of dishonest male signals.