Abstract

We investigated the sex specific effect of Serratia marcescens infection through septic injury on two components of fitness, survivorship and adult competitive reproductive fitness in male and femaleDrosophila melanogaster. Under competitive conditions, infected females showed significantly lower reproductive output compared to control females. However, male reproductive fitness was not affected by infection. We did not find any cost of injury and immune deployment in our study indicating that the fitness cost resulted only from sustained infection or virulence. However, the bacteria was found to be pathogenic, growing equally well in males and females and causing about 80% mortality over an eleven day period with no significant difference in mortality between sexes. Thus, such sex specific effects of pathogens on individual components of fitness indicate that the total fitness cost experienced by each sex might be very different, even within a given regime, thereby affecting the evolution of antibacterial immunity.

Key words: Sex-specific effect, fitness, survivorship, Serratia marcescens, Drosophila melanogaster.