Related Experiment Video
Updated: Mar 1, 2026
09:34
Assessing Differences in Sperm Competitive Ability in Drosophila
Published on: August 22, 2013
15.1K
SPERM DISPLACEMENT WITHOUT SPERM TRANSFER IN DROSOPHILA MELANOGASTER
Lawrence G Harshman1, Timothy Prout2
1Department of Entomology, University of California, Davis, California, 95616.
Summary
Second matings in Drosophila melanogaster reduce the effectiveness of sperm from the first male. This sperm incapacitation mechanism contributes to sperm displacement and the last-male advantage in fruit flies.
Area of Science:
- Reproductive Biology
- Behavioral Ecology
- Genetics
Background:
- Sperm displacement, where the last male's sperm fertilizes most eggs, is common in many species.
- The underlying mechanisms of sperm displacement are not fully understood in most cases.
Purpose of the Study:
- To investigate the role of seminal fluid components in sperm displacement in Drosophila melanogaster.
- To determine if the second male's semen actively incapacitates resident sperm from a previous mating.
Main Methods:
- Females were mated sequentially with sterile males, one with normal semen and one with deficient semen, to assess effects on resident sperm.
- Interrupted copulations were used, varying the duration of the second mating (instant, 2 min, 4 min) to correlate semen transfer with sperm reduction.
Main Results:
- Normal semen from the second male significantly reduced resident sperm numbers compared to deficient semen.
- Longer copulation durations during the second mating (2 and 4 min) led to greater reductions in resident sperm compared to instant interruptions.
Conclusions:
- The findings strongly suggest a sperm incapacitation process mediated by the second male's semen.
- This incapacitation mechanism likely contributes to the sperm displacement phenomenon and last-male advantage in Drosophila melanogaster.
- The identified mechanism may be relevant to sperm displacement in other species where the process remains unclear.
