Dynamics of sperm quality in passerine birds

In many animal species, female mate with multiple males, which leads to competition among the ejaculates from rival males for fertilisation of eggs (i.e. sperm competition). Differences in sperm quality between males can affect the outcome of sperm competition. For example, males that produce longer sperm fertilise more eggs when in competition with males producing short sperm. Similarly, sperm swimming speed influences fertilisation success under conditions of sperm competition between males. In birds, studies investigating the impact of sperm quality on male fertilisation success measure these traits using digital image analysis of sperm length and specialised software that tracks the speed of individual sperm cells. Importantly, these analyses are typically performed on a single sample collected from each male. However, it is currently unclear whether sperm quality varies over successive ejaculates, and therefore whether or not data gained from a single sample is representative of a male.

 

In this project, you will measure sperm quality (sperm length and swimming speed) in sequentially collected ejaculates from male birds in order to investigate the potential for within-male variation in sperm quality. Samples have already been collected and thus are immediately available for analysis. Nonetheless, the student will have the opportunity to collect additional samples during the project period. The project will include handling and sampling of birds (house sparrows), microscopy, digital image analysis of sperm morphology and the use of computer-assisted sperm analysis software to measure sperm swimming speed. The student will also take a leading role in the statistical analysis of the data collected and can use these data and analyses for a report. Finally, the student will develop their research skills and there is the opportunity for them to come up with their own additional research questions (within the scope of the project) if desired.

 

Department of Animal Ecology Netherlands Institute of Ecology, NIOO-KNAW